How Food Works. The Facts Visually Explained ( PDFDrive )

FWHOOOOWRDKS



FWHOOOOWRDKS

Editorial consultant Contributors CONTENTS Dr. Sarah Brewer Joel Levy, Ginny Smith Project Art Editors Senior Editor Duncan Turner Rob Houston Francis Wong Editors Steve Woosnam-Savage Lili Bryant Wendy Horobin Designers Janet Mohun Gregory McCarthy Martyn Page Francesco Piscitelli Illustrators Mark Clifton US Editor Phil Gamble Margaret Parrish Mike Garland Managing Art Editor Jacket Editor Michael Duffy Claire Gell Senior Jacket Managing Editor Designer Angeles Gavira Guerrero Mark Cavanagh Jackets Design Development Manager Producer, Pre-production Sophia MTT Catherine Williams Producer Publisher Anna Vallarino Liz Wheeler Art Director Publishing Director Karen Self Jonathan Metcalf First American Edition, 2017 Published in the United States by DK Publishing 345 Hudson Street, New York, New York 10014 Copyright © 2017 Dorling Kindersley Limited DK, a Division of Penguin Random House LLC 17 18 19 20 21 10 9 8 7 6 5 4 3 2 1 001–300198–May/2017 All rights reserved. Without limiting the rights under the copyright reserved above, no part of this publication may be reproduced, stored in or introduced into a retrieval system, or transmitted, in any form, or by any means (electronic, mechanical, photocopying, recording, or otherwise), without the prior written permission of the copyright owner. Published in Great Britain by Dorling Kindersley Limited. READER NOTICE How Food Works provides information on a wide range of food science and nutritional topics and every effort has been made to ensure that the information is accurate. The book is not a substitute for expert nutritional advice, however, and you are advised always to consult a professional for specific information on personal nutritional matters. The authors, contributors, consultants, and publisher do not accept any legal responsibility for any personal injury or other damage or loss arising from any use or misuse of the information in this book. A catalog record for this book is available from the Library of Congress. ISBN: 978-1-4654-6119-3 DK books are available at special discounts when purchased in bulk for sales promotions, premiums, fund-raising, or educational use. For details, contact: DK Publishing Special Markets, 345 Hudson Street, New York, New York 10014 [email protected] Printed in China A WORLD OF IDEAS: SEE ALL THERE IS TO KNOW www.dk.com

Our diet history 8 STORING 46 AND COOKING 48 FOOD 12 50 FUNDAMENTALS 14 How fresh is fresh? 52 16 Preservation 54 Nutrition basics 18 Chilling and freezing 56 Hunger and appetite 20 Fermentation 58 Flavor 22 Raw foods 60 Smell and taste 24 Food processing 62 Digesting nutrients 26 Additives 64 Carbohydrates 28 Cooking Fiber 30 How food cooks Protein 32 Safe cooking Fats 34 Cholesterol 36 Vitamins 38 Minerals 40 Water 42 Convenience foods Whole foods Too much or too little?

TYPES OF FOOD Red meat 68 Phytochemicals 110 DRINKS 152 White meat 70 Leafy vegetables 112 154 Cuts of meat 72 Brassicas 114 Drinking water 156 Processed meats 74 Root vegetables 116 Coffee 158 Meat substitutes 76 The onion family 118 Tea Fish 78 Vegetable fruits 120 Fruit juice and 160 Shellfish 80 Sweet fruits 122 smoothies 162 Eggs 82 Mushrooms 124 Carbonated drinks 164 Milk and lactose 84 and fungi Energy drinks 166 Yogurt and 86 Nuts and seeds 126 Alcohol 168 live cultures Chilies and 128 Spirits 170 Cheese 88 other hot foods Alcohol and the body 172 Starchy foods 90 Spices 130 Wine Grains 92 Herbs 132 Beer Bread 94 Salt 134 Noodles and pasta 96 Fats and oils 136 Gluten 98 Sugar 138 Beans, peas, 100 Sugar highs 140 and pulses and lows Soy 102 Desserts 142 Potatoes 104 Chocolate 144 Fruit and vegetables 106 Sweets 146 Superfoods 108 Alternative foods 148

DIETS Balanced diet 176 Detoxing 202 FOOD AND 178 204 ENVIRONMENT Do we need Popular diets 206 supplements? 180 208 Feeding the world 228 182 Allergies 210 230 Eating patterns 184 212 Intensive or organic? 232 186 Intolerances Western diets 214 Factory farmed 234 188 Exclusion diets or free-range? 236 Eastern diets 216 238 190 Diet and blood 218 Fair trade 240 Religious and 192 pressure 242 ethical diets 194 220 Food fraud 196 Heart disease 244 Vegetarians 198 and stroke 222 Food waste and vegans 200 224 246 Diabetes Food miles Energy budget Cancer, Genetically Diet and exercise osteoporosis, modified foods and anemia Calorie counting Overfishing and What to eat during sustainable fishing Low-carb diets pregnancy Future foods High-fiber diet Babies and children Intermittent fasting Eating disorders INDEX 248 ACKNOWLEDGMENTS 256

MEAT EATING COOKING When our ancestors Our ancestors developed began to eat meat more than cooking before Homo sapiens 2 million years ago, the extra calories evolved 200,000 years ago. Cooking meat provided, and the reduction in energy made food easier to digest, meaning they needed for its digestion, may have allowed their could extract more calories from it, and didn’t brains to become bigger and more energy-hungry, have to spend so much time and energy chewing as the gut became smaller. However, meat was rare for and processing it. In addition to broadening their diets, most ancient humans, so they would still have relied cooking may have allowed their jaw muscles and guts to heavily on plants, including wild grains. become smaller, and their brains to expand further. 800,000 ya 70,000 ya 15,000 ya Archaeological evidence More widespread evidence of controlled fire of cooking hearths Invention of bread (unleavened) 2 million years ago (mya) 1 mya 500,000 years ago (ya) 50,000 ya 10,000 ya Our diet history 12,000 ya Goat domesticated Diets have changed dramatically during human evolution, often 9,500 ya causing our bodies to change in response. Dating these changes is Rice cultivated challenging. Cooking may have originated 300,000 or 1.8 million 9,000 —8,500 ya years ago, depending on how experts interpret archaeological Sheep domesticated and genetic evidence. Despite this, scientists are building WHY a picture of how our dietary history has affected us. ARE MANY ASIAN PEOPLE Dietary milestones INTOLERANT TO MILK? Our anatomy and physiology have evolved as our diet has Intolerance to lactose in milk is changed over many thousands of years. Some of these pivotal more prevalent in people from events, such as meat eating or cooking, happened so long ago Asia, because domestic cattle that our bodies have already evolved accordingly. Whether we were introduced there much are suited to more recent changes is still to be seen. What has become clear is that some aspects of the modern diet, with its more recently than in abundance of energy-dense foods, can be very detrimental to other parts of our health. Looking back in time may even help us to eat more the world. healthily today.

GREAT COLUMBIAN EXCHANGE HOW FOOD WORKS 89 Our diet history When Europeans first THE SWEET TOOTH met the native peoples of the For our ancestors, sweet food was a rare delicacy. Americas in the 15th and 16th Honey and ripe fruits were a great source of centuries, there began an unprecedented energy, but were scarce or seasonal. Today, we are exchange of foods that one or the other surrounded by accessible, sweet food all the time, population had never seen before. Potatoes and and our liking for it has contributed to an epidemic corn rapidly became staples in the Old World, and of obesity and its related diseases. sugarcane flourished when taken to the Americas. 8,000 ya EUROPE, ASIA, 1800 bce 997 ce 1911 ce Cattle domesticated AND AFRICA Chocolate drunk Word “pizza” Home AMERICAS in Central America first used in Italy 7,000 ya refrigerators Sugarcane 6,000 ya appeared cultivated Cheese invented and in the US alcoholic drinks invented 5,000 ya 1 ce 1000 ce 2000 ce 6,000 ya 4,000 ya 1585 ce Chicken domesticated Maize cultivated; Chocolate introduced to Europe leavened bread 8,000 ya invented in Egypt Potato cultivated The cultivation of grain allowed Humans have traded food humans to settle. This made having for thousands of years, but until more children easier and they quickly fairly recently, only long-life products out-competed hunter-gatherers in could be transported over extended distances. most areas. However, their limited diets and The development of refrigeration and freezing, tightly packed populations meant they had along with faster shipping, have meant that, poorer health than hunter-gatherers. if you can afford them, foods from all over the globe can be on your table. FARMING REFRIGERATED GLOBAL SUPPLY CHAINS



FOOD FUNDAMENTALS

Nutrition basics For the body to function normally it requires fuel for energy, building materials for growth and essential maintenance, plus a small but vital combination of chemical ingredients to ensure its many metabolic processes run smoothly. The body can make almost everything it needs from the nutrients in a balanced diet. What does the body need? Carbohydrates Carbohydrates An adequate combination of essential are the body’s nutrients in our diet—water, carbohydrates, primary source of proteins, fats, vitamins, and minerals—should energy. The body converts simple enable our bodies to work efficiently and keep sugars and more complex starches us in good health. Beyond basic nutrition, into glucose, which fuels our body there are other nutrients that, although our cells. Whole grains and fruits and body doesn’t necessarily need them, are vegetables that are high in fiber certainly beneficial, such as phytochemicals are the most healthy sources in fruit and vegetables and fatty acids in some of carbohydrates. fish. Nutraceuticals, or “functional foods,” including those containing probiotics SUGAR (see p.87), are believed to have health benefits beyond their nutritional value, Water LARGE INTESTINE including disease prevention. Around 65 percent of the body is made MALNUTRITION up of water. This is constantly being lost Malnutrition results from a diet through digestion, that does not contain the right breathing, sweating, amounts of nutrients. While lack of and urine, and it is carbohydrates and protein can lead critical that water to major development and growth is replenished at problems, deficiency in certain regular intervals. vitamins and minerals can cause specific illnesses. For example, a lack of iron may lead to anemia. Overnutrition occurs when an oversupply of nutrients causes health problems, such as obesity caused by a high-calorie diet. Minerals Present in a wide variety of foods, minerals are vital for building bones, hair, skin, and blood cells. They also enhance nerve function and help to turn food into energy. Deficiencies can cause chronic health problems.

FOOD FUNDAMENTALS 12 13 Nutrition basics Getting what we need Building and maintaining cells When we eat food, it passes into our digestive system to be broken down and Cells are the basic functional units of the human absorbed (see pp.20—21). Most nutrients body that make up its diverse tissues and organs. are absorbed in the small intestine. Every one of our trillions of cells is built and maintained by the nutrients we get through our diet. If, through poor nutrition, our cells are unable to function properly, our tissues and organs can become compromised, leading to the onset of a host of health conditions and diseases. Proteins CELL MEMBRANE Cell support Proteins are broken down into amino CYTOPLASM A broad range of nutrients acids. Although they may be used by support cell formation and the body for energy, their main role NUCLEUS growth. A cell’s main is as building blocks of tissue growth structures are built from and repair. Healthy protein sources CELL STRUCTURE amino acids and some fatty acids, and every cell include beans, lean meat, is fueled by carbohydrates and other fatty acids. STO dairy, and eggs. MACH AMINO 1 in 3 ACIDS THE PROPORTION OF SMALL INTESTINE FATTY Fats PEOPLE WORLDWIDE ACIDS Fats are a rich source of energy and help THAT SUFFER FROM in the absorption of fat-soluble vitamins. MALNUTRITION Essential fatty acids cannot be made by the body and must be obtained from food. The healthiest fat sources include dairy, nuts, fish, and vegetable-based oils. Vitamins WHAT IS A Vitamins are vital “HEALTHY DIET”? to the body’s metabolic processes, A healthy diet is one that especially those linked to tissue growth provides the body with the right and maintenance. Most vitamins can’t be stored in the body, so regular amounts of all the essential intake through a balanced diet is nutrients it needs from a variety essential. As with minerals, a lack of certain vitamins can lead of different food sources. This to deficiency diseases. should help you achieve and maintain a healthy body weight.

Hunger BRAIN and appetite Hunger is vital to our survival, and it ensures 1 Hunger triggers we eat enough for our bodies to function. But a Seeing food can trigger lot of the time we eat not because we are a desire to eat whether or not hungry but because we enjoy food—this is we are hungry. (The same down to our appetite. response is triggered by anticipation of a mealtime). Hunger and satiety The food passes to the stomach via the esophagus. Hunger is controlled by a complex interconnected system including our brain, digestive system, and fat stores. The desire HUNGER GHRELIN to eat can be triggered by internal factors, such as low blood sugar or an empty stomach, or external triggers, such as the KEY Vagus nerve sight and smell of food. After we have eaten, satiety, or “fullness” Ghrelin signals are produced, which tell us we have had enough. Insulin Movement Leptin of food Hunger vs. appetite 2 Empty stomach Appetite is different from hunger, but the two are linked. Hunger When the stomach has been is the physiological need for food, driven by internal cues such empty for around 2 hours, the gut as low blood sugar or an empty stomach. Appetite is the desire muscles contract, clearing out any to eat, driven by seeing or smelling food or something we link last debris. Low blood sugar levels with it. Memory for how much we have eaten is also important exacerbate the feelings of hunger. in appetite, and people with short-term memory loss may eat Levels of a hunger hormone called again soon after eating. Stress can also increase the desire to ghrelin also rise. eat. Some substances can help control appetite by specific actions on the body. Water Grapefruit SMALL INTESTINE PANCREAS Water stretches the stomach, The scent of grapefruit triggering satiety. Satiety is seems to reduce activation short-lived, since water is of the vagus nerve, quickly absorbed and the body reducing appetite. responds to the lack of nutrients. Nicotine Fiber Nicotine activates Foods high in fiber slow the receptors in the emptying of the stomach and hypothalamus, reducing delay the absorption of nutrients, hunger signals. keeping you fuller for longer. Protein Exercise Protein affects the release of High-intensity aerobic various appetite-regulating exercise affects the hormones such as leptin, release of hunger increasing feelings hormones, temporarily of fullness. suppressing hunger.

FOOD FUNDAMENTALS 14 15 Hunger and appetite Hypothalamus receives “full” APPETITE AND OBESITY signal from vagus nerve Brain receives People with a tendency to Hunger “full” signals 6 obesity may respond differently stimulated by external cue to external hunger cues. They The vagus nerve sends signals straight to the hypothalamus, may also be less sensitive to telling the brain that food has the fullness hormone, leptin. been consumed and reducing Unfortunately, taking leptin as the hunger drive. a drug doesn’t help obesity. The body quickly adapts to be even more insensitive to leptin, even at high doses. Leptin released to no response ADIPOSE TISSUE LEPTIN SATIETY 5 Leptin travels Cravings to brain Fat cells release a hunger-inhibiting Cravings are a dramatic and specific hormone called leptin. After eating, desire for a certain type of food, and more leptin is secreted and we feel most of us have experienced them. INSULIN full. (Conversely, leptin levels Occasionally, they are caused by specific VAGUS NERVE decrease with fasting, making us nutrient deficiencies, and may be the feel hungry.) body’s way of telling you about the problem. But mostly they are purely IRON STOMAC 4 Pancreas psychological, driven by stress or CHALK releases insulin boredom. Normally, craved foods are The stretching stomach high in fat or sugar (or high in both), H STRETCH RECEPTORS and the rise in glucose which trigger a rush of pleasurable in the bloodstream, chemicals in the brain when eaten. triggers the release of It may be this feeling that we crave insulin. This allows the rather than the actual food. conversion of glucose to glycogen (in the liver) and then to fat. Insulin may also make the brain more sensitive to satiety signals. ADIPOSE WHY DOES MY (FAT) TISSUE STOMACH RUMBLE WHEN I’M HUNGRY? 3 Stomach stretches SOAP As the stomach fills, After eating, your stomach Strange tastes stretch receptors detect muscles contract to push food Some people, especially expansion, causing hunger- through to the intestines. With pregnant women or very reducing chemicals to be young children, experience released. (Liquids, including an empty stomach, this still cravings for nonfood water, stretch the stomach happens, but with nothing to substances, including soil, temporarily, but are quickly chalk, iron, and soap. absorbed, so hunger returns.) dampen the sound, you Psychiatrists call this “pica.” Glucose released hear the growls! into bloodstream from digested food

Flavor Sour Vietnamese dipping sauce We eat food not only because we need to, but also uses a mixture of sour lime juice, because we enjoy it, and this is at least in part down salty fish sauce, and sweet palm to its flavor. Flavor is a combination of the taste and sugar, along with garlic and chili, to smell of food, which combine with input from our activate almost all the receptors on other senses to produce a pleasurable experience. your tongue at once. Sour tastes are produced when taste buds detect What gives food flavor? hydrogen ions. These come fromDIPPIN acidic foods such as fruits You detect smell when volatile chemicals travel into your nose— either before you eat the food or when it is in your mouth. At the and vinegar. same time, the tongue and mouth detect five basic tastes, which G SAUCE combine with the smell to produce flavor. Other senses contribute too—touch and hearing tell you about the food’s texture. Even the MANGO color of a food can impact how we perceive flavor— STRIPS a study showed that changing the color of orange squash affected people’s ability to identify its flavor correctly. COULD THERE BE Sweet VIETNAMESE MANGO SALAD UNDISCOVERED TASTES? Another of the basic tastes is sweetness. Your sweet receptors It is quite likely; some argue respond to sugars such as fructose that metallic tastes are a (in fruit) and sucrose (table sugar). separate category, while Some artificial sweeteners, such calcium’s chalky taste can as aspartame, taste much sweeter be detected by mice and than sugar, meaning you can possibly humans, too. use less in foods. DRIED SHRIMP “NEW” TASTES Recently, receptors have been found on our tongues Umami Umami is the most recently that bind to fatty acids, producing a taste of “fattiness.” discovered of the basic tastes— the name is Japanese, and it roughly Whether this is a true sixth taste is still under debate. translates as “savory.” Glutamic acid in foods is detected as umami and it is Another recent study suggested found in high quantities in fermented and aged foods such as dried humans can also taste starch, FRIES but a receptor has not yet been shrimp, soy sauce, and Parmesan cheese. found. Oil-fried chunky fries may trigger both of these proposed new classes of taste.

FOOD FUNDAMENTALS 16 17 Flavor TOMATOES RELEASE 222 Non-taste sensations VOLATILE CHEMICALS THAT GIVE THEM In addition to the five basic tastes, our tongues THEIR FLAVOR and mouths can detect some other sensations that are not classified as tastes. Nerves on the tongue detect temperature, touch, and pain, Bitter and foods that activate these nerves Children often find bitter produce specific sensations. For example, foods unpleasant, but many the carbon dioxide in carbonated drinks adults enjoy bitter tastes such as tea doesn’t only activate our sour taste (including green tea), coffee, and dark receptors. Its bubbles also cause touch chocolate. It is the most sensitive taste, receptors to fire. The two combine to probably because it evolved to prevent us from eating bitter- tasting poisonous plants. produce the fizzy sensation. SPRING ROLLS SENSATION EXPLANATION ETNAMESE TEA Astringent Chemicals in tea and unripe fruit cause a puckering sensation of the mucous membrane and disrupt the saliva film, making the mouth feel dry and rough. VI VIETNAMESE Cooling Menthol in mint sensitizes the cold receptors on TEA Spiciness your tongue, giving a cool, refreshing sensation. Capsaicin chemicals in chili stimulate pain and heat receptors on the tongue, causing a burning feeling. SALTED PE Numbness There is a disagreement as to the cause, but Sichuan pepper produces numbness or a tingling ANUTS sensation, possibly by stimulating light touch receptors. Salty Smell and flavor COFFEE Table salt is sodium chloride, CHOCOLATE and we have sensors in our The smell of food can be different mouths that detect sodium ions. from its taste, despite most of a They are also triggered (though food’s flavor coming from its smell. less strongly) by closely related This is because when food is in atoms, including potassium. our mouth, scent molecules travel up the back of the throat rather than through the nose (see p.19). This changes which molecules we detect, and in what order, creating a difference in the scent perceived. This is particularly noticeable in coffee and chocolate.

Smell and taste Molecules in food dissolve in saliva and register as tastes when they come into contact with your tongue. Airborne volatile molecules released by food are detected by your nose as smells. Perceiving our meals Mucus- Supporting secreting gland cell Molecules released by food in the air or by chewing dissolve when they meet moisture, MUCUS ROELCFEAPCTTOORRSY such as mucus in the nose and saliva in the mouth. They can then be detected Scent molecule Scent molecule OLOFRATCHTIOONNASAL Scent molecule by specialized nerve cells. These cells dissolving in binding to CHEWED transmit electrical signals to the brain, mucus receptor FOOD which identifies and categorizes each smell and taste. Our noses can pick up hundreds Food particle Supporting cell TONGUE of different kinds of smells, but our tongues primarily detect five tastes—possibly more SALIVA (see pp.16–17). Olfactory receptor cell How smell works Your nasal cavity has a thin layer of mucus. When scent molecules dissolve into it, they bind to the ends of olfactory receptor cells. WHY DOES THE SMELL OF COOKING MAKE YOU SALIVATE? When you smell food, sensory information is passed to the brain, which sends nerve signals to the salivary glands. Saliva is produced to prepare for the first stages of digestion. T ASTE BUD How taste works The tongue’s surface is full of taste receptor cells. Chemicals from food and drink dissolved in saliva come into contact with these cells. Taste receptor cell Sensory nerve

FOOD FUNDAMENTALS 18 19 Smell and taste ONE PAPILLA Why do foods have FRESH ROTTEN ON THE TONGUE CAN tastes and smells? CONTAIN HUNDREDS Fresh or rotten? OF TASTE BUDS As the first humans evolved, they made Distinguishing between fresh a wide range of food choices every day. (nutritious) or rotten (potentially To the brain This means we have evolved more taste dangerous) fruit would have Olfactory receptor cells in the receptors than animals who stick to one been helpful for our ancestors. nose and taste receptor cells on the type of food. As infants, we like sweet tongue send nerve signals to the tastes and reject bitter ones—this is brain to register smells and tastes. thought to stem back to our evolutionary past where sweet tastes signaled high- TO BRAIN energy foods and bitterness could be a NERVE SIGNA warning for poison. Our desire for salty and umami (savory) tastes are thought to be driven by our need for salt and other minerals, and for protein. LS SWEET SALTY BITTE R MUCUS E SIGNALS TO BRAIN ORLEFTARCOTNIOANSAL NERV High calorie Vital minerals Sign of poison Sweet foods such as A taste for salt exists Typically, bitter tastes signal honey provide high because sodium is one of poisonous foods, but with amounts of calories. the macrominerals we experience we can learn to need to survive. like some bitter tastes. SALIVA Smelling in reverse WHY DO MEALS ON PLANES TASTE BLAND? Food in the mouth releases scent molecules that waft up the back The dry air on a plane makes our of the throat (retronasal olfaction) mouths dry and our noses stuffy, rather than through the nose interferring with the moist media in (orthonasal olfaction). Most of which molecules from food and drink what you taste is actually made dissolve. This means taste and smell up of smells detected via receptors don’t detect molecules retronasal olfaction. properly. Our sensitivity to sweet and salty foods drops by 30 percent on planes, so in-flight meals are often salted to give them an extra kick. Oddly, umami tastes seem to be unaffected.

Digesting nutrients 1 Into the mouth Chewing breaks food down For your body to absorb nutrients, food must first be broken down— into smaller particles. This creates a this is the process of digestion. Most of the food you eat will reach larger surface area for our digestive your bowel within a few hours, but how long it stays there varies enzymes to work on. Enzymes in the from person to person. Carbohydrates, proteins, and fats all break saliva begin breaking down starches down at different stages of the process—fiber stays relatively intact. (types of carbohydrate) and fats. Teeth chew food SAGLILVAANRDY Enzyme digests starch What happens when we eat? KEY Saliva Enzyme Fat produced digests fat A combination of chewing, crushing, churning, and Carbohydrate by salivary the action of digestive enzymes breaks down large food Enzyme molecules into smaller ones that can be absorbed into Protein gland the bloodstream. Each enzyme has a specific shape, which Fiber means it can only break down certain molecules, so we Muscles in throat push have a number of different types working in our bodies— chewed food down into all the way from our mouth to our intestines. the stomach LIVER ALLBLADD Churning OMACH ESOPHAGUS The stomach moves, G 2 Enzyme digests ST proteins ER BILE DUCT churning the food and breaking it down further. Acid in the gastric juices and enzymes released by glands in the stomach work on proteins and fats, helping turn them into amino acids and fatty acids. 3 Releasing juices FATTY GASTRIC AMINO The liver produces bile, and the ACIDS JUICES ACIDS gallbladder stores and concentrates it. UNDIGESTED Enzyme Acidic liquid from the stomach is neutralized FIBER digests fats by bile, which is alkaline, before it passes through the intestines. Bile also plays an Gastric juices contain important role in digesting fats. enzymes that digest protein and fat

PANCREAS 4 Enzymes in action Bile breaks up fat droplets to help the enzymes process them. In the duodenum (the first part of the small intestine), enzymes from the pancreas digest carbohydrates, DUODENUM proteins, and fats. KEY 5 Absorption Fat globules Simple sugars Next, the mostly digested liquid full of simple emulsified Amino acids sugars, amino acids, fatty acids, and undigested fiber by bile Fatty acids passes along the small intestine, where the majority Enzyme of the nutrients and water are absorbed into the Enzyme Water bloodstream. Fingerlike protrusions called breaks Vitamins VILLI villi increase the surface area of the walls, down fats SMALL INTESTINE helping with absorption. Enzyme Nutrients FATTY breaks down absorbed by villi ACIDS proteins Nutrients absorbed in UNDIGESTED Enzyme breaks AMINO FOOD FUNDAMENTALS blood travel to parts of the FIBER down sugars ACIDS Digesting nutrients body that need them SIMPLE SUGARS Water BLOOD VESSEL absorbed Vitamins HOW MUCH absorbed 6 Fermentation FOOD CAN THE Feces pass slowly through the STOMACH HOLD? large intestine, allowing bacteria to ferment indigestible fiber. Any final water and vitamins (including those Most stomachs can produced by the bacteria) are 20 21 absorbed, and the remains are comfortably fit around 2 pints compacted as waste. (1 liter) of food, but some UNDIGESTED FIBER stomachs can stretch to BACTERIA accommodate much RECTUM larger meals. LARGE INTESTINE

Carbohydrates DO CARBS MAKE YOU FAT? Most of the food we eat contains carbohydrates. Carbohydrates can cause you They include sugar and starches, which provide to gain weight if you eat too our body with energy, and fiber, which is vital many of them, but complex, for a healthy digestive system. high-fiber carbohydrates are a key part of a What are carbohydrates? healthy diet. Carbohydrate molecules are made STARCHES up of carbon, hydrogen, and oxygen atoms, often in the form of hexagonal or pentagonal rings. Unrefined starches Refined starches If the rings are in ones or twos, These are found in foods Only the simpler, more easily they are sugars, but if the rings including whole-grain breads, digested starches are found in combine into unbranched or cereals, and beans. They are broken refined carbohydrates such as branched chains, they become down slowly, releasing energy over a white flour and white rice. They break starches and other complex long period of time. They are also a good down easily in the body, giving a quick source of fiber, vitamins, and minerals. energy rush, but don’t keep you full for long. carbohydrates. Very long, indigestible chains make up dietary fiber (see pp.24–25). In the WHOLE GRAINS BEANS AND WHITE CAKE WHITE body, sugars and starches are RICE BREAD converted into the sugar glucose— LEGUMES SUGARS our body’s primary source of energy. NOT ENOUGH CARBS? Milk and natural sugars Free sugars Natural sugars are found in milk These can be added to food as refined If you don’t eat enough carbs, your products, fruit, and some vegetables. table sugar, but are naturally present in liver converts fats into ketones and The fiber in some of these foods honey, syrups, and fruit juices. These protein into glucose, which are ensures that the sugar is absorbed provide lots of “empty calories” and it is used to generate energy. Ketogenic at a gradual rate. easy to eat too much of them. diets can help weight loss, but not much is known about their long- APPLE BROCCOLI MILK HONEY FRUIT SYRUP term health effects. They can also JUICE give you smelly breath! FIBER Ketone released A LOW-CARB DIET MAY LEAD TO in breath MOOD SWINGS AS CARBS HELP THE BRAIN MAKE A CHEMICAL Smelly breath THAT STABILIZES MOODS caused by ketones

FOOD FUNDAMENTALS 22 23 Carbohydrates How the body uses carbohydrates BRAIN The brain is the body’s most energy- When we eat carbohydrates, our digestive tract breaks them down demanding organ into sugars, which are absorbed into the blood. Glucose is used directly by our various organs and muscles as a source of energy. 3 Using energy Fructose—a simple fruit sugar that bonds with glucose to make Glucose is the table sugar—can only be processed by the liver. People with easiest and most high fructose diets are at higher risk of type 2 diabetes, possibly efficient fuel for the because fructose is more likely to be converted into fat. body. Chemical reactions in our cells convert glucose (or SMALL INTESTINE other molecules if glucose isn’t available) 1 Absorption and into molecules that distribution release energy. Long-chain, starchy carbohydrates need to be broken down into sugars to be absorbed. Digestion begins in the mouth and continues into the small intestine, where the sugars pass into the bloodstream. MUSCLE Glucose BLOOD VESSEL Fructose Muscle cells molecules molecules convert glucose travel in the travel in the blood into energy blood Glucose is used or HEART VER stored by the liver The heart uses LI energy to pump nutrients around the body Glucose travels around the body Some glucose is stored as glycogen, a complex carbohydrate like starch FAT Fructose is either 4 Fat stores converted to glucose Once the liver’s or stored as fat glycogen stores are full, excess 2 The liver’s role glucose is converted into fat If we eat more carbohydrates than we and stored around the body, need to use immediately, the liver stores the excess as glycogen. When blood sugar levels to be used as fuel later if food becomes scarce. drop, the stored glycogen is converted back into glucose to be used by the body.

Fiber Skin of your greens In many plants, the most fiber-rich part Fiber is the part of food that is not broken is the skin. Apple skins, for example, are down by the body, and helps keep your a great source of the insoluble fiber digestive system functioning properly. It cellulose. This type of fiber provides is found in varying amounts in plant foods. structure to the apple's cell walls. APPLE APPLE CELLS Types of fiber Fiber is traditionally characterized into two types. Soluble fiber dissolves in water, making a thick gel. It is found in foods such as fruit, root vegetables, and lentils, and prevents constipation by softening stools. Insoluble fiber is found in foods like cereals, nuts, and seeds. It keeps bowels healthy by Cellulose Plant cell increasing the weight of stools. However, studies have shown that there strands provide is crossover between the two categories and that solubility doesn't always predict how a type of fiber will behave in the body. structure to cell walls Chain FIBER STRANDS CELLULOSE STRANDS CELLULOSE STRAND Sugar molecule Fiber strands Holding it together Fiber is a carbohydrate comprised of The long strands of cellulose in long chains of sugar molecules. However, apples bond together to form a unlike other carbohydrates, they resist rigid framework, which provides digestion in the stomach. This means they support for the cells. reach the large intestine intact. GETTING ENOUGH FIBER Many of us don’t get enough fiber in our diets. Whole grains are the most common source, but refined grains have the fiber-rich outer layer removed, so don’t provide much. The UK recommends 5⁄8oz (18g) a day—although recommendations vary. KEY 5⁄8oz (18g) Amount required to WHEAT CEREAL DRIED FIGS CHICKPEAS BROWN BREAD of fiber reach 5⁄8oz (18g) of fiber 63⁄4oz (186g) 91⁄2oz (260g) 15oz (15oz) 181⁄2oz (514g)

FOOD FUNDAMENTALS 24 25 Fibre COMPLEX FIBER FERMENTING IN COLON VITAMIN K Vitamin production Feeding your intestines bacteria Protection Certain strains of bacteria produce Weak acids produced by vitamins, some of which we can Fiber is an important source of food for your gut fermentation make the colon absorb and use. We get some flora (microbes including bacteria and fungi that less hospitable to bad bacteria, of our Vitamin K this way. live in your intestines) which ferment it into lowering the risk of stomach bugs. FATTY fatty acids they can feed on. Keeping these FATTY ACIDS bacteria healthy is vital—they produce ACIDS enzymes to help digest other foods and influence your health in ways that we are only just beginning to understand. Healthy colon Improving immunity More beneficial bacteria in the Some types of bacteria in your colon increases the mass of gut improve your immune system stools, diluting toxins and by producing inflammation- keeping the bowel healthy. reducing compounds. Fiber and health Cholesterol BLOOD VESSEL Eating plenty of fiber (see pp.198–99) IVER Fiber reduces the risk of heart disease, certain cancers, obesity, and type 2 L diabetes. A high-fiber diet counters the increased risk of colon cancer caused by eating processed meat (see p.219). Unexpected benefit BILE DUCT SMALL Fiber, particularly the soluble kind, binds to INTESTINE bile (a bitter liquid that breaks fats down Cholesterol pulled to tiny droplets), causing it to be excreted. To into the liver in order Fiber and bile replace the bile, the liver must pull cholesterol to produce bile excreted out of the bloodstream, which may explain how fiber lowers the risk of heart disease.

Protein HOW MUCH Protein is a vital nutrient. The proteins we eat PROTEIN DO WE are broken down into their building blocks and NEED EACH DAY? used to make new proteins and other complex molecules needed by the body. While protein can People need around 1g (1⁄32oz) serve as an energy source, its main function is in of protein for each 1kg (21⁄4lb) the creation, growth, and repair of human tissues. of body weight. This would be 55g (2oz) for the average man and 45g (11⁄2oz) for LE the average woman. What is protein? PROTEIN MOLECU A Proteins are chains of small S H O R T PEPTIDE CHAIN molecules called amino acids. While only 21 standard types of amino acid occur naturally in MINO ACIDS humans, they can join together in any combination, meaning that there are millions of different types of protein available. When you eat foods containing protein, your body breaks them down into amino acids, then Bond between Free amino acids, reassembles them into different two amino with all peptide sequences, producing whatever acids types of protein it needs. bonds digested away An important property of proteins is their ability to fold and twist in Protein Protein fragment Protein components on themselves, which gives each Proteins are giant, complex Shorter chains of amino acids Amino acids are small protein its distinctive shape. This molecules made of many are called peptides. They form molecules made mainly of is what allows proteins to have so amino acids connected in when protein is digested, but carbon, oxygen, hydrogen, many different uses in the body. a chain, which often folds the body also makes them for and nitrogen. There are into a compact shape. many purposes. 21 types in the human body. Why are certain amino ll essential amino acid Eight amino acids Eight amino acids acids “essential”? A s At some point in our evolutionary history, we lost the ability to BEEF WHEAT LEGUMES make nine of the amino acids our body needs. This means we Complementary protein sources must consume these “essential” Some foods such as beef have all the essential amino acids you need, but others do amino acids in our food. Proteins not. Wheat is low in the amino acid lysine but high in methionine, whereas legumes containing an abundance of all tend to have enough lysine but have lower levels of methionine. Combining these nine of them are called “complete.” two sources of protein can provide all the essential amino acids you need. Most animal products are complete proteins, but so are quinoa, tofu, and some nuts and seeds.

FOOD FUNDAMENTALS 26 27 Protein How we use protein DNA PROTEIN IS The body converts some PRESENT IN Dietary protein, once digested amino acids into chemical “bases,” EVERY ONE into amino acids, is involved in which, once assembled in order, OF OUR BODY’S making a huge number of vital are the components of DNA that TRILLIONS molecules, from DNA to hormones spell out its genetic code. OF CELLS and neurotransmitters. Most amino acids, however, are Base within assembled into new proteins. DNA Some of these form the structures of our body, such as muscles. DNA STRAND Many others act as enzymes— molecular catalysts that trigger and control the body’s vital chemical processes. Cell membrane proteins Hormones A cell’s membrane is its outside Our body uses hormones to send layer. Proteins embedded in it messages between different areas. allow communication with the Many hormones, including adrenaline, cell’s surroundings—for example, are proteins or peptides. They are by allowing molecules to pass across. made by glands and organs. CELL PROTEIN MEMBRANE Adrenaline ADRENAL GLANDS KIDNEY AMINO ACIDS Muscle proteins NERVE Muscles are made mainly of straight, CELL long-chain proteins, which form muscle fibers. We need to eat proteins to build our Neurotransmitter muscles, and also to repair damage that Neurotransmitters our muscles suffer when we use them. Some amino acids are used to make neurotransmitters, which MUSCLE are molecules that carry messages between nerve cells throughout our brain and nervous system.

Fats Fats are essential for our body’s health. They provide energy, store excess calories for later use, and have a variety of other roles in the body, from forming cell membranes to making hormones. Carbon atom Glycerol holds the three fatty acids together until they are What are fats? broken down in the body Along with carbohydrates and proteins, GLYCEROL Hydrogen fats make up one of the three main classes of atom macronutrients. Fats in food come as triglyceride molecules. These are made of carbon, hydrogen, SATURATED FATTY ACID Oxygen and oxygen atoms arranged so the carbons MONOUNSATURATED FATTY ACID atom form three long chains called fatty acids, POLYUNSATURATED FATTY ACID joined by a short chain called glycerol. Each Omega end— carbon can bond to other carbons with a the carbons single or a double bond; the number and position of these double bonds changes in the chain are the type of fatty acid and its effect counted from here in the body. The fatty acids making up a fat molecule can be the same or different, giving a huge number of possible types of fat. Fat molecule This triglyceride, or fat molecule, has one of each type of fatty acid. The straight one is a saturated fatty acid, made only of single bonds. If a chain has one double bond, its shape is bent and it becomes a monounsaturated fatty acid. More double bonds make polyunsaturated chains with complex shapes. WILL FAT Bent fatty acids, such The third carbon MAKE ME FAT? as oleic acid, found in from the omega Fat is highly calorific, so olive oil, have one end is the first can contribute to weight gain, double bond with a double but compared to sweet foods, bond, making this Stearic acid, found in meat, is polyunsaturated it makes you feel full for chain an omega-3 longer after eating, so a little fully saturated with hydrogen— fat may help stop you from fatty acid there is no room for any more snacking later! hydrogen atoms Each carbon-carbon double bond excludes two hydrogens, which would otherwise bond with the carbons; since it is short of two hydrogens, it is not saturated with hydrogen—it is “unsaturated”

FOOD FUNDAMENTALS 28 29 Fats Fats in the body Brain and nervous tissue ESSENTIAL FATTY ACIDS are rich in fat—the brain In addition to their use as energy is 60 percent fat and The human body can make most of stores, fats play many other crucial needs a steady supply the fats it needs from other fats or roles. Fats help us absorb and use raw materials. Only two fatty acids some vitamins (see pp.32–33) and are BRAIN are truly essential, because we can’t involved in constructing and repairing make them—the omega-3 fatty acid, nervous tissue. They maintain healthy Steroid hormones, alpha-linolenic acid and the omega-6 skin and nails and are used to make such as testosterone fatty acid, linoleic acid. Both hormones that control blood and estrogen, are are found in nuts and pressure, the immune system, made from fats seeds, especially linseed. growth, and blood clotting. Some other omega-3 Fats also form the basis of all oils are almost the membranes in the body, essential because the surrounding each cell and the body isn’t very good structures within it (see p.30). at making them (see fish, pp.78–79). Fat is stored in subcutaneous FAT STORE (under-skin) deposits and also in FLAX PLANT, deeper deposits around organs SOURCE OF LINSEED Fat or oil? MORE THAN 20 TYPES OF The word fat is often used to describe items that are solid at room FATTY ACIDS temperature, such as butter and lard, while oils are liquid. As a rough ARE FOUND rule, oils contain more unsaturated fatty acids. For many years, it was IN FOODS common to solidify vegetable oil by hydrogenating those fatty acids to make margarine—a supposedly healthy alternative to butter. The A trans fatty acid is often fats produced have since been found to be so unhealthy that straightened, but with a kink margarine is now solidified by adding naturally solid palm oil instead. Oleic acid is bent Stearic acid is straight Oils Fats Hydrogenated fats Unsaturated fats have at least Saturated fats contain no double Trans fats are made by some fatty acids with at least one bonds, and their chains are straight. hydrogenating vegetable oils— double bond. They are found in Their molecules pack tightly, so they a process that adds hydrogen to vegetable oils, nuts, and seeds. The solidify easily, forming solids at room unsaturated double bonds, saturating bends introduced by their double temperature. They are found in animal them and straightening their chains. bonds give their molecules awkward products, such as butter and meat, This forms solid fat, such as that in shapes that do not pack together, and also in palm and coconut oils. margarine. Trans fats have been linked to a range of health issues so they stay liquid at room BUTTER and are being phased out of temperature. many products. OLIVE OIL MARGARINE

Cholesterol A waxy, fatlike substance found in CHOLESTEROL IN THE DIET every cell of our bodies, cholesterol is made by the liver, and it is vital for Humans can make all the LIVER DIET normal body function. If too much cholesterol they need mainly 67–75% 25–33% builds up in the blood, however, in the liver, but they gain extra problems such as heart disease can in the diet—either directly result. But the link between diet, from foods such as eggs cholesterol, and cardiovascular health and meat, or, in some is more complex than we thought. people, because saturated fats, trans fats, and some carbohydrates boost their liver’s cholesterol production. Crucial chemical Fluid inside cell Cell membrane is water-based is a thin, flexible Cholesterol is needed to manufacture some hormones, outer envelope vitamin D, and bile acids, which form an ingredient of Small structures digestive juices (see pp.20–21). It also keeps our cell within cell are membranes—the thin layer surrounding every cell— flexible but firm. The liver regulates our cholesterol each enclosed by level, regardless of cholesterol in the diet, but a diet too a membrane rich in certain foods can make some people produce too much (see p.214). CELL MEMBRANE Membrane made mainly CELL Internal membranes are of oily chemicals called made the same way as phospholipids the cell membrane MEMPRBORTAENINE Cholesterol stiffens Cell membrane the central part Each of our cells has a membrane formed of two layers of molecules. Cholesterol embedded within these layers prevents the membrane from becoming too fluid or too stiff, and gives it just the right permeability to allow the correct types and numbers of minerals and other substances to pass through. It also helps certain proteins attach to the cell—these are vital for communicating with the rest of the body. THE HUMAN BODY CONTAINS AROUND 40Z (100G) OF CHOLESTEROL

FOOD FUNDAMENTALS 30 31 Cholesterol Cholesterol Protein Transporting fat Cholesterol Fatty substances, including cholesterol, Protein cannot mix with our water-based body fluids, so they need to be bundled into a water- Phospholipid Phospholipid friendly capsule to be transported around the Low-density lipoprotein (LDL) body. Cholesterol is packaged into tiny High-density lipoprotein (HDL) These larger particles contain more capsules called lipoproteins, which come in HDL particles are dense, because cholesterol, and a smaller proportion two major types. The larger type, LDL, is they contain more protein and less of their weight is protein. referred to as “bad cholesterol,” because its cholesterol and other fatty parts. function is to deliver cholesterol to the blood, where excess can build up. HDL, or “good cholesterol,” takes cholesterol out of the blood. The cholesterol cycle Cholesterol cycles between the liver and the blood, BLOOD VESSEL Bad cholesterol performing vital functions. The process relies on a PLAQUE Increased LDL in the balance between the two lipoproteins—HDL and blood can cause cholesterol- LDL. If you have more LDL than HDL circulating, filled plaques (atheromas) plaques can build up in arteries, which can raise to build up, narrowing the blood pressure and lead to heart disease (see arteries and increasing pp.212–15). High LDL levels can be due to diet, blood pressure. If the plaque obesity, or genes. ruptures, blood clots can form, cutting off Liver removes blood supply. cholesterol from body in the form LIVER of bile salts HDL removes Liver converts excess cholesterol cholesterol into bile from plaque acids and recycles or excretes them PLAQUE LDL adds HOW DO cholesterol STATINS WORK? to plaque Statin drugs lower Good cholesterol cholesterol by slowing the HDL particles transport excess liver’s cholesterol production. cholesterol from the cells, Statins have many drawbacks, blood, and plaques back to however, such as impeding the liver. High HDL levels mean that more cholesterol the body’s ability to use is removed, reducing cholesterol to make plaque formation. vitamin D.

Vitamins A group of micronutrients found in different types of food, vitamins are essential for our body’s growth, vitality, and general well-being. Most of us can get the majority of the vitamins we need from a healthy, balanced diet, but in some cases, supplements can be useful. What are vitamins? Fat-soluble Vitamins are organic compounds that Some of the vitamins our body needs dissolve in fat. play an essential part in controlling our This means they are mainly found in fatty foods, such as oily body’s metabolic processes. Some, such fish, eggs, and dairy foods, rather than fruit and vegetables. Fat- as vitamin C and E, act as antioxidants, soluble vitamins aren’t absorbed properly by the body if they are which are thought to benefit the consumed without any fat, which means that supplements of these vitamins taken body by neutralizing excess free Vitamin without the right food may be less effective. discovery radicals (see pp.111). We need In the 1800s, doctors THE LIVER CAN STORE only tiny amounts, but the realized that some ENOUGH VITAMIN A TO LAST THE BODY 2 YEARS lack of them can impair diseases were caused not by germs, but by body function and lead nutrient deficiencies. to deficiency diseases. Animal experiments Vitamins are classified using different diets and supplements led according to whether to the discovery of they dissolve in fats these micronutrients. or water. Storage of vitamins Vitamin A Vitamin D Needed for vision, Aids uptake of some Our body can store fat-soluble vitamins in the growth, and development. minerals. Low levels can liver, so we don’t need to eat them every day. Lack of vitamin A can lead lead to calcium deficiency But because of this, if we take in too much, to poor vision or blindness, and poor bone health, levels can build up in the body and become especially in children. including rickets in children. toxic. Water-soluble vitamins can’t be stored and any excess is excreted in urine. This means we need to consume them more frequently. Water-soluble vitamins ingested often Liver stockpile LIVER Liver stores Vitamin E Vitamin K Fat-soluble vitamins fat-soluble An antioxidant. Needed to make are stored in the same vitamins Protects cell membranes, blood-clotting agents. Low cells that store fat, maintaining healthy skin consumption can lead to mainly in the liver and eyes, and strengthens disorders in blood clotting, but also elsewhere the immune system. bleeding, and bruising. in the body.

FOOD FUNDAMENTALS 32 33 Vitamins Chickpeas WHERE IS KEY Leafy greens VITAMIN F? Meat Broccoli Poultry Avocado The gaps in the vitamin Liver Tomatoes Fish Bananas alphabet are left by substances Oily fish Oranges Tuna Strawberries once thought to be vitamins, but Eggs Nuts Egg yolk Peanuts later reclassified. Some were found Milk Olive oil Rice not to be vital. Vitamin F, though Whole-wheat bread essential, was found to be a pair Water-soluble of fatty acids that were better classified as fats instead Water-soluble vitamins of vitamins. are found in a wide variety of foods, including fruit, vegetables, and protein-rich foods. Because they dissolve in water, these vitamins can easily be lost in food preparation, for example, through the boiling of vegetables. The B vitamins, together called the vitamin B complex, are often grouped in supplements and are sometimes found in the same foods. Vitamin B1 Vitamin B2 Vitamin B3 Helps generate Important for Maintains the energy and ensures muscles metabolism and healthy nervous system and brain, and nerves function well. skin, eyes, and nervous the cardiovascular system Low levels may cause system. Deficiency produces and blood, skin, and headaches and irritability. weakness and anemia. metabolism. Vitamin B5 Vitamin B6 Vitamin B7 Important for Involved in nerve Biotin. Needed for metabolism and in the function, metabolism, and healthy bones and hair, and production of neuro- making antibodies and fat metabolism. Lack of B7 transmitters, hormones, haemoglobin. Deficiency can cause dermatitis, muscle and hemoglobin. can affect mental health. pain, and tongue swelling. Vitamin B9 Vitamin B12 Vitamin C Folic acid. Vital for Involved in An antioxidant. healthy infant development. metabolism and making red Helps the growth and repair Deficiency in an expectant blood cells. B12 deficiency of various tissues throughout mother increases the risk can lead to a condition the body. Deficiency can lead of spina bifida in her baby. called pernicious anemia. to poor wound healing.

Minerals Like vitamins, we need minerals to function properly. Our bodies require seven “macrominerals” in relatively large amounts, and only minute levels of other “trace minerals.” Minerals occur naturally in certain foods, so a balanced diet should provide sufficient mineral intake but supplements may be necessary in cases of deficiency. KEY Sodium Magnesium Potassium Ready meals Regulates the amount Found in bones and Involved in muscle Red meat of fluid in our bodies. Low inside all cells; needed for and nerve activity and fluid Bacon sodium levels can cause a immune system, muscle, and balance. Low levels can Fish wide range of effects from nerve health. Deficiency may cause muscle cramps and Fish bones headaches to comas. lead to muscle problems, abnormal heart rhythms. Shellfish vomiting, and heart issues. Eggs Egg yolk Chloride Minerals Milk An important Cheese component of stomach Minerals come from rocks or Cereals acid. It is very rare to soil and dissolve in groundwater to Whole grains lack this mineral. become charged particles, or ions. Crisps Leafy greens Plants absorb these ions into their Lettuce tissues through their roots and the Broccoli minerals reach us through the food Tomatoes chain. “Macrominerals” are the Bananas Nuts minerals we need in the Olives largest amounts. Drinking water Tea Sulfur Phosphorus Calcium An essential part Needed for bone Essential for keeping of many proteins, it is health, and involved in the our bones and teeth strong, important for building process that releases energy and has many other roles in new body tissues. from food. Very low levels the body, including nerve can cause muscle weakness. and muscle functioning.

FOOD FUNDAMENTALS 34 35 Minerals MINERAL DEFICIENCIES Tiredness YOU CAN GET caused by ALL THE SELENIUM Deficiencies in mineral intake can lack of iron YOU NEED EACH cause various health problems. DAY FROM JUST For example, long-term calcium Nausea can ONE OR TWO deficiency can lead to reduced bone be caused BRAZIL NUTS density and osteoporosis; lack of iron by lack of may cause anemia, with weakness and fatigue; and the early symptoms of magnesium magnesium deficiency include nausea. For each of these, dietary changes or supplement use may be recommended. Copper Fluoride Needed by many Helps keep our bones enzymes and for iron and teeth strong. Lack of metabolism. Although fluoride may lead to an very rare, deficiency increase in tooth decay. can cause anemia. Manganese, chromium, Trace minerals molybdenum, nickel, silicon, vanadium, cobalt Minerals needed in only Also needed in tiny amounts by the body are miniscule amounts. called trace minerals. Despite the fact that we need so little of them, trace Iodine minerals are no less important than Important for normal thyroid macrominerals. They include iron—a function. Deficiency can lead to mineral often deficient in our diets. developmental problems and physical or learning disabilities. Selenium Iron Zinc An antioxidant that Allows red blood Forms part of many helps protect our cells from cells to carry oxygen, enzymes without which stress. People dependent on and helps with energy our bodies can’t function produce grown in selenium- production. Iron deficiency normally. Deficiency is linked poor soil risk deficiency. anemia is quite common. to diarrhea and pneumonia.

Water DRINKING CAN YOU DRINK WATER TOO MUCH WATER? Up to 60 percent of our body weight is water and it is needed to keep our organs If you drink too much too functioning. While we can live without food quickly, cells swell as water for several weeks, without rushes in. Swollen brain cells water, death occurs in days, cause headaches, dizziness, showing just how important it is. and confusion. In severe Hydration BRAIN cases, water poisoning Getting enough water keeps our skin can lead to death. plump and elastic, helps regulate body temperature, and ensures our kidneys filter Dehydration out waste. If the water concentration in the blood is too high or too low, the body If more water is lost than taken in, compensates by moving water into or out symptoms of light-headedness and of our cells; both can be damaging. tiredness can start within hours. Thirst is the body trying to correct the problem A hydrated brain before it becomes severe. In extreme Water is vital for the brain to function. cases, dehydration causes fits, brain The balance between water and the damage, and death. substances dissolved in it is important for neurons to transmit signals effectively. Decreased attention and memory If you become dehydrated, brain tissues shrink, Moist eyes EYE and it takes more effort to carry out simple To keep the eyes clean tasks. Attention, mood, memory, and reaction and comfortable, they are time can be affected, and you may even continually moistened with become more sensitive to pain. tears, the major component of which is water. EYE Blood flows easily BLOOD VESSEL Dry eyes Blood fluid (plasma) is 92 percent Dehydration slows tear water. The liquid allows oxygen-carrying production which can leave red blood cells, infection-fighting white the eyes feeling dry, irritated, blood cells, and other vital components and gritty. to flow easily to where they are needed. Low blood pressure If dehydration is severe, the water content of your blood falls. Blood becomes thick and viscous, making it difficult for your heart to pump it around the body. This can lead to low blood pressure, dizziness, and fainting.

Regulating hydration INTESTINES HOW MUCH DO I NEED? We lose water mainly through urine, The amount of water you need varies but some evaporates from the skin, or depending on the climate and what is breathed out. The kidneys regulate you spend your time doing. Eight water levels in the body and prevent glasses per day (2–3 quarts/liters) is blood from becoming too concentrated frequently advised for moderately or dilute. If water levels in your body active people in temperate climates, tissues or cells fall, thirst is triggered. but this includes fluid from other drinks and food. For young, healthy Fluids outside SALTY people, the best thing to do is to cells, such as SNACK listen to your body and drink when blood, drop you feel thirsty! However, elderly in volume Water people can become dehydrated levels in without feeling thirsty, and so Water cells drops must watch their water intake. levels in cells don't fall Salt Water WATER SOUP JUICE drawn out of cell FOOD FUNDAMENTALS Water Thirst due to Thirst due to Water aids digestion Constipation THE BODY STARTS less water high salt intake In your stomach, acidic If you are dehydrated TO ABSORB Sensors in your heart The salt concentration liquid, some of which is and food passes through WATER AS SOON and arteries respond of blood fluid water, helps churn and the large intestine, your AS 5 MINUTES when blood volume increases if excess salt digest your food. As the body absorbs water AFTER DRINKING falls by 10 percent is consumed, causing processed food passes from it. This leaves or more, and signal water to be drawn through your intestines, stools dry and hard, thirst. Drinking tops from cells. If salt liquid keeps it moving easily. causing constipation. up the liquid in your concentration rises blood, increasing the by 1 to 2 percent, 36 37 volume of blood. thirst is triggered. Pale urine BLADDER Concentrated urine When you are well hydrated, your urine When you are dehydrated, the kidneys reduce the is a pale straw color. If you drink a lot, a amount of water excreted, retaining water in the blood. Urine gets darker in color due to substances more dilute urine is produced. dissolved in the urine becoming more concentrated.

Convenience foods With busy lives, many of us turn to ready-made WHAT MAKES convenience foods. They are quick, easy, and tasty, JUNK FOOD but not usually the healthiest option. So why are convenience foods bad for us? And are there SO MOREISH? healthier types we can choose? Most junk food carefully What are convenience foods? balances sweetness, salt, and Convenience foods are preprepared or processed and include fat – designed to give our prepackaged meals, cake mixes, snack foods, preprepared fruit and brains maximum pleasure vegetables, frozen ingredients, and canned food. Companies that and keep us coming back make and sell convenience foods usually focus on taste and shelf-life rather than on nutritional value. By exploiting our evolved affinity for for more. sweetness and our desire for quick, easy, tasty, high-calorie food, they ensure products sell in high quantities. 50 High in refined carbs MILLION AMERICANS The flour used is refined and ARE SERVED AT FAST processed, removing most of the FOOD RESTAURANTS fiber and micronutrients, but EVERY DAY leaving the high calorie count. High in fat In addition to the oil in the noodles themselves, the noodles are often fried to dry them, making them high in fat. High in salt and sugar Lots of salt and sugar is added to make the bland noodles tasty. This can often exceed our daily recommended amounts. Instant noodles Low in fiber and protein Just adding water to instant There is little fiber or noodles provides a tasty, filling protein in instant noodles, snack. However, they contain so despite their high calorie few beneficial nutrients and count, they won’t satisfy have been linked to increased you for long. risk of obesity, diabetes, heart disease, and strokes.

FOOD FUNDAMENTALS 38 39 Convenience foods Modern eating habits Influence of takeouts A study has shown that people who are exposed to Ready-made food is all around us, from more takeouts at home, near work, or on their route sandwich shops to takeout to fancy between the two, eat more takeouts and are more restaurants, and this affects the way we likely to have a higher body mass index. eat. When working hours are long and time for food preparation and cooking is short, HOME the appeal of instant, fast food rises. However, there can be a trade-off between TAKEOUT convenience foods and health. One, or a few, takeouts Fewer takeouts ROUTE BACK FROM WORK passed on the way home consumed TAKEOUT HOME ROUTE BACK FROM WORK Many takeouts passed More takeouts on the way home consumed History of GOOD CONVENIENCE FOODS CARROT AND convenience foods CILANTRO SOUP Not all convenience foods are unhealthy. Canned and Convenience food is not new. Food frozen fruit and vegetables, or ready-made soups, are can be preserved in many ways; good sources of nutrients and fiber—sometimes frozen, canned, dehydrated, or by containing more vitamins and phytochemicals than using additives. For some, this has their fresh ingredients (cooking tomatoes releases improved nutrition, but for others it lycopene). But sugar and salt are often added to has made it worse. improve the taste and preserve the soup for longer. 1810 Cans 1930s Flash-freezing Late 1960s 1970s Number first used to invented, allowing Freezers and of women in work preserve food foods to be frozen frozen prepared increases, leading to for sailors on en masse and sold meals become a rise in the popularity long voyages. to the public. mainstream. of preprepared meals. 1894 Corn flakes 1800 invented by Dr. John 1953–54 The first 2000 Harvey Kellogg. This ready-to-eat meals was one of the first sold, in a metal tray 1967 Countertop 1979 The first ready-to-eat cereals that could be heated microwave ovens chilled ready to be mass produced. in an oven. introduced—but it meal, launched would be 20 years by a supermarket before they were in the UK. common in the home.

Whole foods ARE WHOLE FOODS THE SAME AS ORGANIC? First introduced in the 1940s, the whole foods movement is still increasing in popularity. Its focus Organic foods are crops on eating unprocessed food is likely to increase fiber grown with natural fertilizers and micronutrient intake, providing health benefits, or pesticides or animals reared but it can be limiting if taken to the extreme. on organic feed—they are a All natural type of whole food. But, Raspberries have the highest whole foods are not amount of omega-3 fatty acids in always organic. any raw fruit. Also, 31⁄2 oz (100 g) of raspberries contains more Nutrients and minerals than one-quarter of your A whole-food diet is likely to contain a daily needs of vitamin C. good variety of vitamins and minerals. Raspberries are particularly high in vitamins C, K, and manganese. What are Antioxidants whole foods? Whole foods such as raspberries are rich in potentially beneficial Whole foods are the opposite antioxidants (see pp.108–09). of processed foods—they are in However, sometimes these can their natural form, or processed as be added artificially to foods. little as possible. They might include Fiber fresh fruit, vegetables, meat, fish, whole grains, Plant foods that are less nuts, and seeds. Some proponents argue whole processed tend to contain more foods must also be organic, but there is little fiber. High fiber intake benefits evidence for the health benefit of organic foods. weight loss and protects against certain diseases (see pp.198–99). Good fats Whole foods don’t contain the damaging trans fats common in processed products and many are high in beneficial unsaturated fats. Fewer additives Whole foods are “as nature intended,” without added flavorings or preservatives. However, this means they often don’t have as long a shelf life as processed versions.

FOOD FUNDAMENTALS 40 41 Whole foods Necessary processing Not all foods are safe to eat without some degree VITAMIN C VITAMIN E of processing. Some, especially meats, need to be prepared or cooked to destroy toxins or kill dangerous bacteria. Others, such as tomatoes, become more nutritious when cooked (see p.55). Whole-food proponents advise doing this processing yourself, and keeping it to a minimum. However, even a little chopping can VITAMIN A affect the nutrition of foods. Vitamin leakage Coverings and peels such as apple skin protect the fruit’s vitamins. Once exposed to air, a small portion of the vitamins (particularly vitamin C) react with oxygen and are lost. Whole-foods movement 1960s Consumers 2016 Whole-foods in the western world (“clean-eating”) Farmers and consumers in Europe start to take an interest diet comes back in the 1920s started to seek out in food nutrition. into fashion. foods grown without insecticides. These natural foods were coined 1900 2016 “whole foods” by Frank Newman 1980s First Whole Foods Turner, a British organic farmer, in 1940s Frank Newman Market opens in Texas, 1946. The “clean-eating” diet in the Turner was the first to selling exclusively developed world has seen whole promote whole foods. organic, natural foods. foods rise in popularity. DRAWBACKS OF WHOLE FOODS 5 OZ (150 G) A strict whole-food diet can be expensive and OF STRAWBERRIES time-consuming to prepare, and difficult to stick to PROVIDES YOU WITH at social occasions or restaurants. It can also take a ALL OF THE VITAMIN C while to get accustomed to the taste of fresh food YOU NEED IN A DAY that contains less sugar and salt, if you are used to processed food. PREP TIME

Too much or too little? Nutrients such as vitamins and minerals are good for us, but that does not mean that more is better. Regularly consuming too much of some vitamins, such as vitamin A, can be as dangerous as not getting enough of them. PERCENTAGE OF PEOPLE WITH SYMPTOMS OF TOXICITY 100 50 0 RED BONES RRHEA Toxicity FRACTU Nutrients in excess can become DIA toxins. Excess magnesium may cause diarrhea, for instance. Water-soluble TOO MUCH vitamins don’t generally cause long-term problems, as excess is excreted in urine, but fat-soluble vitamins can build up and cause serious damage. Too much vitamin A, for example, can damage your bones. At very high levels, nearly The maximum recommended amount AMOUNT OF NUTRIENT IN THE DIET everyone experiences is where 2.5 percent of people toxicity symptoms develop toxicity symptoms JUST ENOUGH Everyone is different Most people getting enough Setting recommended minimum and maximum The yellow area of the graph levels of a nutrient that works for a whole population is represents the recommended problematic, because everyone's needs are different. A intake of a certain nutrient minimum safe level is often set as the smallest amount that is healthy for most needed by 97.5 percent of healthy people of a certain individuals. age. This establishes a safe limit that applies to most people. The remaining 2.5 percent of people who follow The minimum recommended these recommendations will not get quite enough or amount is where 2.5 percent get a little too much of a certain nutrient. of people develop deficiency symptoms TOO LITTLE At very low levels, everyone EBLEEDS Deficiency experiences deficiency If you are deficient in any essential symptoms nutrients, your body will not function properly. You may experience symptoms, PROBLEMS such as fatigue and headaches. VISION Depending on which nutrient you are NOS lacking, more serious symptoms, such as vision problems (without enough vitamin A) or nosebleeds (without enough vitamin C) can occur. 100 50 0 PERCENTAGE OF PEOPLE WITH SYMPTOMS OF DEFICIENCY

FOOD FUNDAMENTALS 42 43 Too much or too little? Food labeling THE DAILY NEEDS OF CHILDREN AND To make things simple, most governments turn your recommended ELDERLY PEOPLE ARE daily need into a single guideline amount for use on packaging. NOT THE SAME AS Some amounts are minimum amounts of essential nutrients, such THOSE FOR ADULTS as minerals. Others are not targets, but guides to upper limits for potentially unhealthy foods, such as salt, to encourage a healthy Nutrition claims diet. Some countries highlight where nutrients in food are likely to exceed your daily need if eaten in excess. Some foods make bold claims on the packaging about what they contain (or Amber means that this Green means that the amount Percentage of do not contain) and the health benefits food contains a medium of sugar in this food is low your daily need they might have. But these claims are tightly regulated, and the food must fit amount of total fat Red means that this certain guidelines to make a specific food contains a lot of claim. The regulations differ slightly between countries, but some European saturated fats Union (EU) examples are given below. ENERGY FAT SATURATES SUGARS SALT 924KJ 0.7G 13G 5.9G 0.8G 220KCAL 12% 19% 30% <1% 11% EACH GRILLED BURGER (94G) CONTAINS: Traffic light system CLAIM RULING The UK’s traffic light system Sugar-free was developed by the Food If a food is labeled as sugar-free, it Standards Authority and aims must contain less than 1 percent to make choosing healthy sugar by weight. food easier (in turn avoiding NUTRITION FACTS long-term health effects). Low-fat Low-fat foods must contain Exactly what “high” or “low” less than 3 percent fat by weight. Serving size 1 cup (228g) means depends on the food Servings per container 2 or drink and portion size, but more green on a label Calories 250 suggests a healthier food. Calories from Fat 110 Labeling is not color coded % DAILY VALUE High If they claim to be high in fiber, Recommended daily values in fiber foods must have at least 6 percent Total Fat 12g 18% for nutrients such as fat and fiber by weight. Saturated Fat 3g 15% salt are maximums, not targets Trans Fat 3g Percentages of daily need Source of A food can be called a source of 10% Many countries, including the vitamin D vitamin D if it provides 15 percent Cholesterol 30mg 20% US, have food labels that show of your daily need per 31⁄2oz (100g). Sodium 470mg 10% quantities of each nutrient as a Total Carbohydrate 31g percentage of your daily need. They also show the total Dietary Fiber 0g 0% calories per serving. Quantities Reduced- Reduced-fat products must Sugars 5g of certain micronutrients (such fat contain 30 percent less fat than Protein 5g 4% as iron) must also be shown. a similar product. This does not Vitamin A 2% mean it is necessarily low in fat Vitamin C 20% compared to other foods! Calcium 4% Iron MACARONI AND CHEESE



STORING AND COOKING

How fresh SUNLIGHT is fresh? WRINKLING Freshness has become an important concept in evaluating the quality and desirability of Post-harvest, a food. But what does “fresh” actually mean? combination of a What are the factors influencing freshness loss of water supply, and how do food labels help us to assess the sunlight, and wind freshness of food? can cause wrinkling Decreasing freshness From ripe to rotten A complex combination of physical While some fruit and vegetables and organic processes operates only reach peak ripeness or on a piece of fruit to affect its desirability after harvesting, most freshness and determine the rate foods will start to lose flavor and at which it declines. nutritional value from the moment they are harvested or butchered. This is the point at which a number SHOULD I of processes that make foods spoil FREEZE FOOD AS begin. These include the release of SOON AS I BUY IT? destructive enzymes; the natural breakdown processes, such as One common myth is that BRUISING oxidation, that degrade nutrients; food must be frozen on the day and the growth of microbes as defense mechanisms in the food’s of purchase. In fact, you can cells start to stall. In some fruit and freeze food at any time up vegetables, natural metabolic to the use-by date on and physiological processes may the label. actually accelerate after harvesting. Time limit for freshness? Harvest Air freight To avoid damage and More perishable foods, such Some plant foods can remain fresh increase shelf life, most as berries, are more likely for remarkably long periods, if fruit and vegetables are to be air-freighted to stored correctly. Potatoes can stay harvested by hand. consumer countries. fresh for three months in a cool, dark place. Pears and apples can 0 1-3 be stored for up to a year in special DAYS DAYS atmospherically controlled facilities. 1-4 Food’s journey FREIGHT TIMELINE Refrigerated ships WEEKS Produce such as fruit and vegetables grown in the Refrigerated ships can provide southern hemisphere will pass through many highly controlled temperatures to stages on its journey to markets in the US. keep produce as fresh as possible.

STORING AND COOKING 46 47 How fresh is fresh? Bacteria may feed on, BACTERIA Loss of nutrients degrade, and digest Nutrients are lost at an accelerating rate as a food’s exposed parts of food freshness declines. They are particularly affected by oxidation, heat, sunlight, dehydration, and enzymes. Vitamin C can be extremely vulnerable to degradation over time, although this varies between foods. Chilling and freezing are especially helpful in delaying or preventing nutrient loss. Vitamin C Larvae feed on apples, Effects of chilling affecting their freshness Broccoli stored for and sometimes causing seven days at 32ºF them to drop too early (0ºC) can retain most of its vitamin C, compared to 44 0ºC/32ºF 20ºC/68ºF percent when stored APPLE SAWFLY LARVA at 68ºF (20ºC). MEANING ENZYMATIC BREAKDOWN LABEL TYPE Oxygen seeps Sell by There is no legal requirement to show this date; into apple it is used more to help retailers manage stock. Display until Similar to “Sell by,” this label is used by retailers to help manage their stock levels. Best before The “Best before” date refers to food quality, rather than safety. CELL Enzyme Use by In some countries, this label has legal force. reacts with Food is not safe for use after this date. Enzyme oxygen released Brown color produced by Types of date labels from cell melanins, brown pigments, Date labels on food are supposed created by reactions between to inform the consumer, but can enzymes, tannins (type of acid), be confusing. and oxygen Retailer 45 Advanced stock management techniques allow retailers to PERCENT OF ALL minimize wastage and guarantee THE FRUIT AND appropriate stock levels. VEGETABLES PRODUCED 1-3 1-3 0-7 ARE WASTED DAYS DAYS DAYS Distribution center Consumer Handling is kept to a The end goal is to ensure minimum and conditions that the produce reaches continue to be tightly the consumer at or before controlled. its peak ripeness.

Preservation SPICES AND HERBS WERE USED AS The very things that make food nutritious PRESERVATIVES BY also make it vulnerable to contamination ANCIENT CIVILIZATIONS and degradation, so preserving food has always been a key concern of food science and cultures since ancient times. Types of preservation Chilling and freezing Chemical Reducing temperature Artificial preservative Natural processes, including decreases the rate of chemicals, such as nitrates, microbial growth, oxidation, biochemical reactions. are commonly used in foods heat and light, and the action of Freezing suspends them. such as meats (see pp.74–75). enzymes can contaminate foods Drying Canning or degrade them by breaking down Water is necessary for most In addition to sealing food, their key components. The rate biochemical activity, so canning also involves of the biochemical reactions that removing moisture can extreme heat treatment drive these processes depends on prevent microbial growth. to kill off any microbes. favorable conditions, so altering Salting Smoking these in different ways can help to Increasing the concentration Smoking infuses foods with preserve foods. Some preservation of salts in food kills most a variety of antimicrobial, methods, such as drying, have microbes by dehydrating antioxidant, and acidifying been used for tens of thousands them. compounds. of years. Artificial chemical Pickling Storing preservatives are common Making food more acidic Storing food in cool, dark today—but their implications can kill many microbes but conditions prolongs its shelf life, for our health remain uncertain. will also affect the food’s as will reducing exposure to taste and characteristics. oxygen and ambient microbes. How nutrients degrade NUTRIENT LEVEL OF STABILITY NUTRIENT LEVEL OF STABILITY Some categories of nutrients, such Proteins, Relatively stable Vitamin B1 Highly unstable; sensitive as vitamins and antioxidants, are carbohydrates (thiamine) to air, light, and heat reactive since they are composed of fragile molecules. Such vulnerable Fat Can become rancid Vitamin B2 Sensitive to light and heat molecules will degrade naturally Vitamin A (see p.74), particularly (riboflavin) Relatively stable over time, a process that speeds up at higher temperatures Vitamins greatly with heat, physical damage, B3 (niacin), exposure to sunlight, and exposure Sensitive to air, light, B7 (biotin) to oxygen – the last of which and heat generates destructive free radicals (see p.111). Different nutrients are Vitamin C Highly unstable; sensitive Vitamin B9 Highly unstable; sensitive more sensitive to certain threats to air, light, and heat (folic acid) to air, light, and heat than others. Vitamin D Somewhat sensitive Carotenes Sensitive to air, light, to air, light, and heat and heat