COLLEGE LEVEL Nutri ti on
NUTRITION
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TABLE OF CONTENTS Preface....................................................................................................... 11 Chapter 1: What is Food Made of? ............................................................. 15 Nutrition 101 .................................................................................................................. 15 Nutrients to Build Body Tissues .................................................................................... 16 Macronutrients .............................................................................................................. 18 Carbohydrates ................................................................................................................ 18 Proteins .......................................................................................................................... 18 Fats and Oils................................................................................................................... 19 Water .............................................................................................................................. 19 Fiber ............................................................................................................................... 20 Vitamins ......................................................................................................................... 20 Minerals ......................................................................................................................... 21 Eating a Balanced Diet ................................................................................................... 21 What are Staple Foods? ................................................................................................. 23 Digestible and Indigestible Foods ................................................................................. 25 Indigestible Food Components ...................................................................................... 26 Important Points from this Chapter .............................................................................. 28 Chapter 1 Questions ....................................................................................................... 29 Chapter 2: How and Why We Eat .............................................................. 32 Food in the GI Tract ....................................................................................................... 32 Alimentary Tract Landmarks......................................................................................... 35 Accessory Digestive Organs ........................................................................................... 37
What Happens After Nutrients Get Absorbed? ............................................................. 39 Appetite and the Appetite Centers in the Brain ............................................................ 40 The Microbiome ............................................................................................................. 41 Culture and Diet Choices ............................................................................................... 42 What Makes a Healthy Diet? ......................................................................................... 44 Important Points from this Chapter .............................................................................. 45 Chapter 2 Questions....................................................................................................... 46 Chapter 3: Carbohydrates ......................................................................... 49 Mono and Polysaccharides ............................................................................................ 49 How Carbs get Made and Broken Down ....................................................................... 53 Regulating Carbohydrate Levels .................................................................................... 56 Recommended Allowances for Carbs ............................................................................ 58 Soluble versus Insoluble Fiber....................................................................................... 58 Alternative Sweeteners .................................................................................................. 58 Important Points from this Chapter .............................................................................. 60 Chapter 3 Questions....................................................................................................... 61 Chapter 4: Fats.......................................................................................... 64 Purpose of fats................................................................................................................ 64 Fatty Acid Types ............................................................................................................. 66 Why Cook with Fats? ..................................................................................................... 70 Fat Recommendations in the Diet ................................................................................. 72 Fat Replacers .................................................................................................................. 72 Important Points in this Chapter................................................................................... 74 Chapter 4 Questions....................................................................................................... 75
Chapter 5: Proteins ................................................................................... 77 Purpose of Protein and its Sources in the Diet .............................................................. 77 How Proteins are Made ................................................................................................. 79 Protein Synthesis without Adequate Amino Acids........................................................ 79 Breakdown of Proteins ................................................................................................... 81 What is Nitrogen Balance? ............................................................................................ 83 Protein Intake Recommendations ................................................................................. 83 Proteins and Vegetarians ............................................................................................... 84 Important Points from this Chapter .............................................................................. 85 Chapter 5 Questions ....................................................................................................... 86 Chapter 6: Vitamins and Minerals............................................................. 89 Important Vitamins ....................................................................................................... 89 Vitamin A .................................................................................................................... 89 Thiamine ..................................................................................................................... 90 Riboflavin ................................................................................................................... 90 Niacin .......................................................................................................................... 90 Pantothenic Acid ............................................................................................................ 90 Pyridoxine ...................................................................................................................... 91 Cobalamin ................................................................................................................... 91 Biotin .......................................................................................................................... 91 Ascorbic Acid .............................................................................................................. 91 Choline ........................................................................................................................ 92 Calciferol ..................................................................................................................... 92 Alpha Tocopherol ........................................................................................................... 92
Folic Acid ........................................................................................................................ 93 Phylloquinone ................................................................................................................ 93 Minerals in the Diet ....................................................................................................... 93 Calcium ....................................................................................................................... 93 Chloride ...................................................................................................................... 94 Chromium ................................................................................................................... 94 Copper ........................................................................................................................ 94 Fluorine ...................................................................................................................... 94 Iodine .......................................................................................................................... 94 Iron ............................................................................................................................. 95 Magnesium ................................................................................................................. 95 Manganese .................................................................................................................. 95 Molybdenum............................................................................................................... 95 Phosphorus ................................................................................................................. 96 Potassium ................................................................................................................... 96 Selenium ..................................................................................................................... 96 Sodium ........................................................................................................................ 96 Sulfur .......................................................................................................................... 97 Zinc ............................................................................................................................. 97 Mineral and Vitamin Deficiencies ................................................................................. 97 Folate Deficiency ........................................................................................................ 98 Niacin Deficiency ........................................................................................................ 98 Riboflavin Deficiency ................................................................................................. 99 Thiamin Deficiency .................................................................................................... 99
Vitamin A Deficiency .................................................................................................. 99 Vitamin B6 (Pyridoxine) Deficiency ........................................................................ 100 Vitamin B12 Deficiency ............................................................................................ 100 Vitamin C Deficiency .................................................................................................101 Vitamin D Deficiency ................................................................................................101 Vitamin E Deficiency .................................................................................................101 Vitamin K Deficiency ................................................................................................ 102 Zinc Deficiency ......................................................................................................... 102 Iron Deficiency ......................................................................................................... 102 Important Points in this Chapter................................................................................. 104 Chapter 6 Questions..................................................................................................... 105 Chapter 7: Water and Electrolytes ........................................................... 108 The Importance of Water ............................................................................................. 108 Which Electrolytes are Most Important? .....................................................................110 Acid-Base Balance ......................................................................................................... 112 Water-related Disorders (Dehydration, Water Intoxication, Heat Illnesses) ............. 113 Dehydration ............................................................................................................... 113 Water Intoxication .................................................................................................... 114 Heat-related Injuries .................................................................................................... 114 Heat Stroke ................................................................................................................ 115 Heat Exhaustion ........................................................................................................ 115 Rhabdomyolysis ........................................................................................................ 115 Heat Syncope ............................................................................................................. 116 Heat Cramps .............................................................................................................. 116
Important Points in this Chapter.................................................................................. 117 Chapter 7 Questions ...................................................................................................... 118 Chapter 8: Other Essential Nutrients ...................................................... 120 Phytonutrients ............................................................................................................. 120 Lignans ......................................................................................................................... 120 Resveratrol .................................................................................................................... 121 Carotenoids ................................................................................................................... 121 Curcumin...................................................................................................................... 122 Ellagic acid ................................................................................................................... 122 Flavonoids .................................................................................................................... 123 Glucosinolates .............................................................................................................. 123 Allicin ........................................................................................................................... 123 Choline ......................................................................................................................... 124 Antioxidants ................................................................................................................. 124 Why Don’t Antioxidant Supplements Work? .......................................................... 126 Top Foods High in Antioxidants .............................................................................. 126 Important Points in this Chapter................................................................................. 129 Chapter 8 Questions .................................................................................................... 130 Chapter 9: Having a Healthy Body Weight ............................................... 133 Body Composition ........................................................................................................ 133 How do We know What is a Healthy Body Weight? ................................................... 136 BMI Calculations...........................................................................................................137 Waist Circumference Measurement ............................................................................ 139 Genetic and Other Factors on Body Weight ................................................................ 139
Reading Nutrition Labels............................................................................................. 140 Safely Losing and Gaining Weight............................................................................... 143 Following the Diet Circles ............................................................................................ 145 Important Points in this Chapter................................................................................. 147 Chapter 9 Questions..................................................................................................... 148 Chapter 10: Nutrition and Physical Activity ............................................. 150 How Muscles are Fueled .............................................................................................. 150 Fueling Exercise ........................................................................................................... 152 How Activity affects Energy Needs .............................................................................. 154 Eating for Athletics ...................................................................................................... 154 Important Points in this Chapter................................................................................. 158 Chapter 10 Questions ................................................................................................... 159 Chapter 11: Nutrition and How it Supports Health .................................. 162 Determining the Optimal Nutrition ............................................................................ 162 Serving Sizes ................................................................................................................ 164 Food Group Recommended Servings Per Week ......................................................... 164 Nutrigenomics and Nutrigenetics ............................................................................... 166 Specialty Diets and Heathy Diet Prescriptions ........................................................... 167 The FODMAP Diet.................................................................................................... 168 DASH Diet ................................................................................................................ 169 The Gluten-free Diet ................................................................................................. 170 Diabetes Diet .............................................................................................................172 Important Points In This Chapter ................................................................................175 Chapter 11 Questions ................................................................................................... 176
Chapter 12: Disorders related to Food ...................................................... 179 Diabetes mellitus.......................................................................................................... 179 Type I Diabetes ............................................................................................................. 181 Prediabetes .................................................................................................................... 181 Type 2 Diabetes ............................................................................................................ 182 Metabolic Syndrome .................................................................................................... 183 Food Intolerances and Food Sensitivities ................................................................... 184 Eating Disorders .......................................................................................................... 186 Important Points in this Chapter................................................................................. 190 Chapter 12 Questions .................................................................................................... 191 Chapter 13: Food Safety and Food Technology ........................................ 194 Foodborne Illnesses ..................................................................................................... 194 Protecting against Foodborne Illnesses....................................................................... 199 Food Spoilage ............................................................................................................... 201 Organic Food and Organic Technology .......................................................................202 GMO Foods ..................................................................................................................202 Important Points in this Chapter.................................................................................204 Chapter 13 Questions ................................................................................................... 205 Summary ................................................................................................ 208 Course Questions and Answers ............................................................... 212 Answers to Questions.............................................................................. 253 Chapter 1 ...................................................................................................................... 253 Chapter 2 ...................................................................................................................... 254 Chapter 3 ...................................................................................................................... 255
Chapter 4 ...................................................................................................................... 256 Chapter 5 ...................................................................................................................... 257 Chapter 6 ...................................................................................................................... 258 Chapter 7 ...................................................................................................................... 259 Chapter 8 ......................................................................................................................260 Chapter 9 ...................................................................................................................... 261 Chapter 10 .................................................................................................................... 262 Chapter 11 ..................................................................................................................... 263 Chapter 12 .................................................................................................................... 265 Chapter 13 .................................................................................................................... 266 Course Questions ......................................................................................................... 267
PREFACE If you are taking this course on nutrition, you probably already have some idea that there is more to the study of nutrition than the four basic food groups and the food pyramid. Nutrition has become a vast topic of discussion in many areas of health and the sciences. As you will learn, the substances we take in as food every day become part of us in our entirety. This means that most of us need to pay a great deal more attention to what we put in our mouths than we are. This course will give you the basics of the different biochemical molecules found in the food we eat and will teach you why we need them. You will learn about the importance of water, electrolytes, and minerals in the study of many aspects of nutrition, including nutrition for athletes, food insecurity and food safety, disorders related to nutrition, and much more. In this course, you will likely learn much more than many doctors learn about the topic of nutrition in medical school. Sit back and see if you can find ways to incorporate what you learn in your own life as well as in your future profession, whatever that may be. In chapter one of the course, you will study the basics of food, including what it is made from. Food can be anything that is edible to humans. Your food is made from a variety of substances called macronutrients. You might recognize these as carbohydrates, protein, and fat. All food is made from these three types of macromolecules. You also consume micronutrients like vitamins and minerals. You will be introduced to these basic food components and will learn what fiber is and why it is indigestible. Chapter two in the course is a nice discussion of what happens to the food we eat after taking a bite of it. All substances absorbed into the body must be extremely small; this means that your bite of food must become millions of molecules of tiny fragments of food. We will also talk about why you eat at all. People will eat food that is not even appetizing, simply because of a complex mechanism of feeding and satiety centers in the brain that tell us to eat. We will also talk about the cultural and religious influences of food choices in society and about what makes for a healthy diet.
Chapter three will help you feel more comfortable talking about carbs. You'll see how carbohydrates are either simple or complex and where they come from in the everyday diet. The chapter talks about how plants make and store the carbohydrates they produce. It also covers the way animal cells use carbohydrates for energy and how glucose levels are regulated in humans. You will be introduced to insoluble and soluble fiber and you will learn their nutritional benefits. Finally, you will study the various types of artificial and alternative sweeteners. Chapter four covers the fatty components of the diet. Believe it or not, fats are necessary for a healthy diet. You will learn what the best fats look like and which are not at all good for you. Even so, there are fat replacers from many different sources used to give the taste and feel of a delicious, fatty diet – even when you are eating something low in fat. The different types of replacers are covered in this chapter. After reading this chapter, you will know which types of fatty foods are best to eat and why they are so good for you. Protein is the last of the main calorie-producing macronutrients to study and is the topic of chapter five in the course. It is the only organic source of nitrogen in your diet and is crucial for building cell structures. Enzymes are almost always made from proteins and, without proteins like hemoglobin, the transfer of gases in the human bloodstream would be nearly impossible. You will learn where proteins come from, how they are made inside your cells, and how you break them down when they are not necessary. Finally, you will learn about what makes a complete protein and how people on restricted diets get the protein they need to sustain life. Chapter six covers the micronutrients, vitamins and minerals in the everyday diet. While needed in much smaller quantities compared to the macronutrients, you will see how much you need these in your diet just as much as those other nutrients. Vitamins are carbon-based molecules that serve many different functions in the biochemistry of your body. Minerals, on the other hand, are not carbon based but are still needed equally. In this chapter, you will learn the food sources and about the conditions arising when a mineral or vitamin is deficient in the diet. Chapter seven in the course is about water, which is also a macronutrient of sorts, even though it doesn't offer any calories or energy to the body. You will see how important
water is to all living things. You'll notice that water isn't found as pure water in your body but contains numerous electrolytes. You will learn the crucial electrolytes in your diet and whether or not electrolyte drinks are helpful to you. Finally, you will study water-based disorders, such as dehydration and water intoxication – both of which are possibly fatal to you if not prevented and treated. Chapter eight looks at important nutrients you may never have heard of before. They include the many plant-based phytonutrients usually linked to all of the bright colors you see in these foods. Choline is another nutrient gotten from foods or taken as supplements by some health enthusiasts. There is also a lot of buzz about antioxidants in food; you should know what an antioxidant is and why they are important to your health. Chapter nine is an excellent lesson on what it means to have a healthy weight and how to achieve it. You will study body composition, the body mass index, and how to know what happens if a person is out of the normal range of what we call "healthy". There is more in this chapter on how to read nutrition labels and how to safely gain or lose weight. Fad diets and common diets like the paleo and vegetarian diets are also covered in this chapter. Chapter ten in the course teaches you about nutrition and athletic performance. You'll see that muscle is mostly protein but that it doesn't feed off protein during normal exercise. You will learn how muscles use energy, how to fuel yourself before, during, and after physical activity, and how to eat for the best athletic performance. There are a lot of so-called fitness experts that claim to have the sports nutritional supplements you'd need but you will see in this chapter that regular food is best to sustain health and physical activity. Chapter eleven studies nutrition and how much of an important factor it is in supporting health. You will learn about the Dietary Guidelines for Americans 2020 to 2025, which looks at what is known about diet and our health. Newer topics called nutrigenomics and nutrigenetics are introduced, which involve studies researchers are doing to look at individual ways your diet can be tailored to your genes and how food affects your genetic
makeup. Many people are on medically-approved diets or special diets due to existing health issues, which are covered in this chapter as well. The focus of chapter twelve in the course is food-related disorders. There are more of these illnesses than you would think. Diabetes is common and is related to food because it involves the lack of ability to process a major part of our diet. Food sensitivities, intolerances, and allergies are all different phenomena related to the inability to tolerate a certain food. You will learn the differences between these disorders in this chapter. We also discuss eating disorders that commonly affect a person's food intake in one way or another. Chapter thirteen looks at food safety issues and different types of food technology you've probably heard of already but don't fully understand. Foodborne illnesses are common if food isn't prepared or stored properly. Anyone studying nutrition should know which foods are more likely to cause which food-related infections. Preventing these illnesses in the first place is preferable to treating them later. We will also talk about food technology, especially organic foods and the increasing prevalence of GMO foods in the world.
CHAPTER 1: WHAT IS FOOD MADE OF? In this chapter, you will study the basics of food, including what it is made from. Food can be anything that is edible to humans. Your food is made from a variety of substances called macronutrients. You might recognize these as carbohydrates, protein, and fat. All food is made from these three types of macromolecules. You also consume micronutrients like vitamins and minerals. You will be introduced to these basic food components and will learn what fiber is and why it is indigestible.
NUTRITION 101 Nutrition isn't just about food; it is about the interaction between the food you eat and your body. Food contains certain types of nutrients. The nutrients are the helpful parts of food; all nutrients are digestible to some degree. We use the term digestible to indicate food that you ingest, and that gets absorbed into your gastrointestinal tract. Much more happens to food after it is digested; you will learn a lot more about exactly how this all works. Food is divided into carbohydrates, protein, and fats. Carbohydrates can be divided into sugars, starches, and fiber. They are combined together because they are made of the same simple sugar molecules. There is more than one type of fat as well. Fatty acids are the type of fat used to store energy in your body, while cholesterol is used to make vitamins and as part of the cell wall of each of your cells. A nutrient, by definition, is any active chemical ingredient in your food that has a true role in your body. Nutrients must be digested by the GI tract before they can be used by our body. Micronutrients get their name because they are needed in very small quantities in your food. They do not add any energy to the body but are important in other ways. Nearly all the food you eat is made from some mixture of nutrients. Even food you think of as being only made from protein, such as meat, contains other things, such as fat and
micronutrients. When you talk of the different types of food, you need to think of them as being made of some percentage of sugar, starch, fiber, fat, oil, protein, water, vitamin, and mineral. By the end of this course, you will know which food groups contain the different substances in food. Food has three main purposes: to build body tissues, to produce energy for immediate use and storage, and to maintain health. You need to consume enough food to get all the essential nutrients to sustain life. Water is just as important to consume as any nutrients you can eat. There is no such thing as a nutrient better for you than any other. They each have their role in the body, so all nutrients are necessary in some balanced way. You also need to consume some fiber, even though none of it gets introduced beyond the digestive tract.
NUTRIENTS TO BUILD BODY TISSUES Your body is made entirely of nutrients. You should know the approximate nutrient content of a typical adult human body. A person weighing 110 pounds or 50 kilograms will be approximately 68 pounds of water, 20 pounds of protein, 15 pounds of fat, and 6.6 pounds of minerals. You can see from this that protein is the main bodybuilding nutrient you need to eat. Are you surprised at how much of your body is fat? You need fat to keep your body warm, to build cells, and to store energy. The mineral in the greatest quantity in your body is calcium. You might remember calcium as being an important part of your bones and teeth. Children need nutrients in order to grow and develop. A child's body is always growing and making new cells. Each cell divides into new cells that grow and need nutrients too. Children need different quantities of nutrients than adults because of their rapid growth and development. Women in pregnancy also need different amounts of nutrients than nonpregnant women because they are creating a life that needs nutrients as well. The pregnant body also has an increased need for nutrients for the growing uterus and breasts. Adults do not keep the same cells throughout their lifetime. You are replacing cells all the time. Your skin cells, for example, are continually sloughed off and need to be
replaced. The inside lining of the digestive tract needs ongoing replacement as well. The fluids in your body get secreted as part of natural processes; the components of these also need replacing. Anytime there is extra stress on your body or an illness, your body needs to make new cells to repair any that have become damaged. You will soon learn about the nutrients you use for energy. Surprisingly, you do not use fat for the energy that you use every day. This is what you need carbohydrates for. Carbohydrates break down into simple sugars that are absorbed into the body and used immediately by your cells. When these carbohydrates are completely broken down, your cells will make carbon dioxide as a waste product. This is the same carbon dioxide you breathe out from your lungs. When you breathe in, you take in oxygen your cells need to break down these energy-making molecules. Each nutrient type has a different effect on the body. Let's take a brief look at the purposes of each of the nutrients you might eat: •
Carbohydrates – these are used exclusively for energy
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Fiber – these are used for gastrointestinal health and digestion
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Fats - these are used for energy storage, building cells, and for energy usage
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Proteins these are used to build cells, as enzymes in chemical reactions, to protect your body by their effect on the immune system, and sometimes for energy
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Minerals – these are used to build cells, to aid enzymes in chemical process, and to make fluids
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Vitamins – these are used to aid enzymes in chemical processes, and to help build cells
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Water – this is used to make fluids and for most of the chemical processes in the body
The main thing that differentiates macronutrients and micronutrients is the amount of the nutrient you need for daily functioning. Let's look first at the macronutrients.
MACRONUTRIENTS Macronutrients are those things you need to consume in large quantities every day – at least large compared to the micronutrients. Think "grams or pounds of the macronutrients in food" rather than milligrams of the micronutrients. Carbs, proteins, fats, and water are all macronutrients. Each of these, except for water, provides calories to fuel your body. You should remember that protein provides 4 calories for each gram you eat and that carbohydrates also provide 4 calories per gram. Fats are more than twice the calories per gram – at 9 calories per gram. In that sense, fat could make you "fatter" if you only ate this macronutrient and nothing else.
CARBOHYDRATES We will talk much more about carbohydrates in a later chapter. The basic unit of every carbohydrate is some type of simple sugar. A simple sugar usually has 6 carbon atoms on it with 12 atoms of hydrogen and six atoms of oxygen. These can be arranged in many different configurations to make monosaccharides, which is just one sugar unit, disaccharides, which is two sugar units, or polysaccharides – many sugar units in a chain. Most polysaccharides you eat are also called starches. Carbohydrates make up most of the food you eat. Simple carbohydrates are either monosaccharides or disaccharides. Glucose is the most common monosaccharide in the body. When it combines with fructose, it makes a disaccharide you know as table sugar. Fruits, honey, sugar cane, and beets are common sources of sugar. Some long-chain sugars or polysaccharides can be ingested but will not be absorbed into your body. Cellulose is a common plant fiber of this type.
PROTEINS Only about 10 to 35 percent of your calories come directly from protein. Children need these for growth and development, and adults need them to make enzymes and to help
build cells. Some hormones and neurotransmitters in the brain are made from small proteins. Proteins contain carbon, oxygen, hydrogen, nitrogen, and sometimes sulfur. Most people know that meat is a good source of protein; however, if you are a vegetarian, you can still get protein through eating eggs, milk, cheese, nuts, beans, and lentils. This is also a good source of protein. If you were a bodybuilder, you would want to get most of your protein through eating meat because this is a better source of protein than almost any plant source.
FATS AND OILS Fats and oils are good to eat if you need a concentrated source of energy. Even if you are not trying to gain weight, you still need to eat some fat in your diet. Fortunately, there are plenty of healthy fats you can eat. Fats are found in chicken and other meats, milk products, butter, cooking oil, groundnuts, avocado, and even fish. You can divide fats into saturated and unsaturated fats. We will talk more about what this means from a biochemical standpoint later. Most saturated fats are found in meat sources and in milk or butter. Unsaturated fats are found in things like oils. In general, unsaturated fats are healthier for you and will not lead to heart disease as much as saturated fat. Trans fats are processed fats used in foods to prevent them from getting rancid. These fats are not natural and are the worst type of fat you can eat. Most of the time, unsaturated fats are liquid at room temperature, while saturated fats are solid at room temperature.
WATER Expect to find about 31 liters of water or 8 gallons of water in one person weighing 110 pounds. Water is seen in nearly every part of your body. This is why you can't go more than a few days without drinking some water. This can't be said for solid food – you can go a few weeks without any of these. The average adult should drink about 2 to 3 quarts of water per day for maximal health. Drinking is even more important if you are losing a lot of water through sweat or diarrhea.
These are the things you most need water for: •
Making bodily fluids, like tears, GI fluid, cellular fluid, and breastmilk.
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Helping make sweat to cool the body.
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To allow all chemical processes of the body to happen.
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To keep the interior linings of the body, like the eyelid interiors and respiratory tract moist.
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To make urine that helps carry waste products from the body.
FIBER Fiber is a type of carbohydrate that is not digestible because we lack the enzymes to break it down. Sometimes, however, the bacteria in our gut have the necessary enzymes to do this. When they break down the fiber, it gives off gas, which is why too much fiber can lead to this problem. Many vegetables have fiber, like carrots and cabbage; you'll also find fiber in whole grains like wheat flour and barley. The main goals of fiber in the diet are these: •
Food is made bulkier with fiber in the diet, which can make you feel full when trying to lose weight
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Feces will be softer and bulkier in order to prevent constipation
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The absorption of nutrients is slowed down, so sugar isn't absorbed so quickly
These are the macronutrients. Let's talk about the micronutrients.
VITAMINS While you do not need many of these substances in your diet, they are still very important to your health. There are two major groups of vitamins. The first is the fatsoluble vitamins, which are vitamins A, D, K, and E. You need some fat in order to have these vitamins absorb into your system. These are stored in your fat cells for use over time. The second group is water-soluble vitamins. These are folic acid, vitamin C, and B
vitamins. These cannot be stored in the body in fat cells, so you need to consume these regularly. We will talk much more about vitamins in another chapter. You need a very balanced diet of healthy foods in order to get enough vitamins. It is uncommon to get vitamins from processed foods unless they have been added by the manufacturer. An example of this would be milk, which is almost always enhanced by adding vitamin D. Vitamin D deficiencies are not common in developed countries but are more common in the developing parts of the world. In a later chapter, you will learn about the different diseases caused by vitamin deficiencies, such as rickets and scurvy.
MINERALS Minerals are also needed in very small quantities in your diet, which is why these are also called micronutrients. Most minerals are the same as metals you commonly think of, such as iron. In your body, however, they are not in the form you typically think of but are in ionic form, similar to what you would see with sodium. Sodium is also a metal that is almost always seen in its ionic form as a salt. Metal ions are basically salt ions and are components of some type of salty substance. The minerals you need in your diet include sodium, zinc, iron, iodine, fluorine, potassium, selenium, calcium, and phosphorus. We will talk a great deal more about the functions of minerals in the body. Some of them, such as calcium, are used for many different things, such as to build bone and teeth or as part of an enzymatic or biochemical reaction in the body. Others, such as iron, are used as part of the oxygencarrying protein called hemoglobin in the blood. Like vitamins, minerals are almost always only found in healthy and natural foods rather than in processed foods.
EATING A BALANCED DIET A balanced diet is something we will talk about extensively. What is a balanced diet? It is what you think it is, which is a diet made from many different types of foods. You need things like meat, dairy products, fruits and vegetables, and healthy sources of fats. If you have a restricted diet, such as a vegetarian diet or a dairy-free diet, you can still get a
balanced diet by knowing which other foods contain the nutrients you need. By the end of this course, you will know exactly which foods to eat if you are on a restricted diet. There are some things that really don't qualify as being part of a balanced diet. These are things like simple sugars or table sugar, sources of cholesterol, high-salt foods, and alcohol. You can eat a healthy diet without eating any of these things, and eating a large quantity of these items is not healthy for you. None of them except for perhaps small amounts of cholesterol are needed in any type of diet. The food pyramid replaced the "four food groups" in 1992; in 2005, this was replaced by a program called "My Plate". These were designed to help people make good food choices. They are similar, but some nutritionists did not like the fact that the pyramid had a hierarchy where people thought some foods were better than others. Figure 1 shows the food pyramid, and figure 2 shows the MyPlate used today to help people have a balanced diet:
Figure 1. Food Pyramid
Figure 2. MyPlate Some of the My Plate images have fruits and vegetables separate, while others put them together into one group and indicate that you should eat this section the most. Oil, sweets, and other fats should be eaten sparingly. As mentioned, you do not need any type of simple sugars in your diet as long as you get other carbohydrates.
WHAT ARE STAPLE FOODS? In the United States, we don't often think of staple foods. In most parts of the world, however, staple foods are very important. A staple food is usually a grain of some type consumed in larger quantities than most other foods, mostly because it is inexpensive and readily available. The most important thing staple foods provide is energy or
calories, usually to regions of the world where many people do not have enough to eat. The staple food will be different from region to region. Often, people who eat a lot of staple food help make it interesting by adding smaller amounts of vegetables or protein in order to add additional fiber, vitamins, or protein. A common way to add protein to staple foods is to put in beans or other legumes. Small amounts of meat can also be used in these types of foods. Staple foods tend to be in carbohydrates and low in cost to produce. The staple food used in most parts of the world is corn. Places in the world that use corn this way include Mexico and parts of Europe, South America, and the United States. It can be eaten all as sweetcorn or ground up to make a type of flour called cornflower. Corn syrup is made from corn. You can also make cooking oil and whiskey using this staple food. Rice is the second most commonly used staple food. The most likely place to see this as a staple food is in Asia, the Middle East, and parts of Africa. It was actually first domesticated in Southeast Asia and India, where it has been grown for thousands of years. It was transported to South America because of trade, where it helps billions of people survive in many parts of the world. China, India, and Indonesia make the most rice in the world. Wheat is the third most commonly used staple food in the world. It originally grew in the area of Mesopotamia in the Middle East. This is now where all but modern-day Iraq is located. Wheat was most likely the first domesticated crop in ancient times; it remains the most common staple food in much of the United States, Europe, and even China. It is almost always ground up to make flour for baking. Nutritionally speaking, whole wheat flour has more nutrition in it than the typical white flour most people consume. A small but significant number of people consume some type of root as their main staple food. Foods like this are called tubers. Common tubers grown in the world include yucca or cassava, which is the most common tuber eaten in the world. Potatoes are also tubers that were originally cultivated in the Andes Mountains of South America. Once they were brought to Europe in the 1500s, potatoes became a staple food for this area as well. Other common roots or tubers are sweet potatoes and yams.
Soybeans, sorghum, and plantains are also sometimes eaten as staple foods. Soybeans are used for animal feed, although humans also consume them. Sorghum is good when food is needed in climates that are otherwise inhospitable. Plantains are mainly grown in tropical areas of Africa and Latin America.
DIGESTIBLE AND INDIGESTIBLE FOODS Foods can be described as being digestible or indigestible, although most foods have components of both. You might need to deal with people who need a highly digestible diet and those who don't. Digestible foods are those that break down easily and are absorbed readily into your system. People need to eat easily digestible foods when their GI tract is suffering and needs some kind of a break. This might be true with ulcers, gastroesophageal reflux disease, nausea, and vomiting, or irritable bowel syndrome. People after surgery also need a bland and easily digested diet. You can tell if a food is easily digested if it is low in fiber. This is because fiber is the component of food least likely to be digested. A low fiber diet is also called a low residue diet. You will hear much more about this later. Fruits and vegetables tend to be high in fiber unless you cook them. If you make a juice out of a fruit or vegetable, it will also be low in fiber but will still have plenty of nutrients. Foods considered low in fiber include any type of cooked vegetable, dairy products, cooked fruits like applesauce, bananas, white bread or other food made with white flour, hot cereals like cream of wheat, creamy peanut butter, puddings, lean meat, eggs, and most cooked soups. Fried foods are not necessarily indigestible; they are just difficult for many people with digestive problems to eat. Other foods to avoid when trying to eat a highly digestible diet include meat with casings like hot dogs or sausages, heavily processed meats, beans and lentils, carbonated beverages, peanuts and nuts, highly acidic fruit, whole spices, full-fat dairy products, seeds, and raisins or other dried fruits.
INDIGESTIBLE FOOD COMPONENTS Food that is indigestible for everyone is generally some type of fiber. Remember that fiber is any carbohydrate that the body does not have enzymes to break down and absorb into the body. Digestible carbohydrates can be simple carbohydrates or starches, which are long chains of simple sugars that we do have enzymes to break down. For some people, foods containing lactose or milk sugar are indigestible. There are hereditary factors that determine if a person can tolerate lactose or not. You will hear more about this later. Some indigestible carbohydrates get digested instead by the gut bacteria, which make methane or hydrogen gas as an end product of their metabolism. This is where we get flatulence from. Fiber is still healthy for you because it can prevent things like heart disease, colon cancer, and type II diabetes. There are actually many types of fiber we cannot digest, including the fiber that comes from mushrooms and from most plants. You will learn that there are two different types of fiber. There is soluble fiber, which helps prevent cholesterol absorption, among other things, and in soluble fiber, which helps aid digestion. This partial list tells you some common types of fiber and where they come from: •
Cellulose - comes from cereals, fruits, and vegetables
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Chitin - this comes from mushrooms and the shells of crustaceans
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Hemicellulose – this comes from some other cereals, such as bran and legumes
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Hexoses - this comes from wheat and barley
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Pentoses - this comes from Rye and oats
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Lignin - this comes from fruit stones, garden beans, and some cereals
Water-soluble dietary fibers include psyllium, which is a type of hemicellulose inulin, pectin, found in the skin of fruits and vegetables, raffinose, found in legumes, and alginates, which are a number of substances found in algae.
Resistant starch is starch that normally you can digest but becomes resistant to this process. You will find it in pasta, some vegetables, or potatoes allowed to cool after they have been cooked. Unripe fruits, sourdough bread, and raw cornstarch are also sources of resistant starch. They do not break down well in your GI tract and mimic regular dietary fiber. A few types of sugar are indigestible to humans but not by the bacteria in your gut. People who are lactose intolerant will consume indigestible sugar if they drink milk containing lactose. Raffinose, which is a type of sugar in cabbage and broccoli, is also not easily digested by humans alone. Sorbitol can be found in apples and pears. You do not digest sorbitol easily either. As with other foods digested by the gut bacteria, flatulence can result from eating them.
IMPORTANT POINTS FROM THIS CHAPTER •
Food is anything edible; we need food and water to survive, grow, and develop.
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Food can be divided into macronutrients and micronutrients.
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You need large quantities of macronutrients, which are carbohydrates, protein, fats, and water.
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Micronutrients are needed in small quantities; these include vitamins and minerals.
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Staple foods are those eaten in larger quantities for energy, usually among people living in developing countries where food is scarce.
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Foods are either digestible or indigestible. Easily digested foods lack fiber and are often cooked. They help people with gastrointestinal disease or distress.
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Fiber is an indigestible type of carbohydrate. There are many types and sources of fiber, with the most common one being cellulose, a part of the cell wall in plants.
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