Principles of the Science of Nutrition
CH 2 OH Glucose
C. Total Fiber
Portion Size
Grams of
Total Fiber Portion Size
Grams of Total Fiber
Grain Products Green peas ½ c 4
Bran Buds ½ c 12 Carrots ½ c 3
All Bran ½ c 11 Potato, with skin 1 med 4
Raisin Bran 1 c 7 Collard greens ½ c 3
Bran Flakes ¾ c 5 Corn ½ c 3
Oatmeal, cooked 1 c 4 Cauliflower ½ c 2
Bread, whole wheat 1 slice 2 Nuts
Fruits Almonds ½ c 5
Raspberries 1 c 8 Peanuts ½ c 3
Avocado ½ med 7 Peanut butter 2 Tbsp 2
Mango 1 med 4 Dried Beans
Pear, with skin 1 med 4 Pinto beans, cooked ½ c 10
Apple, with skin 1 med 3 Black beans, cooked ½ c 8
Orange 1 med 3 Black-eyed peas, cooked ½ c 8
Banana 1 med 3 Navy beans, cooked ½ c 6
Vegetables Lentils, cooked ½ c 5
Lima beans ½ c 7
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whereas oils are usually liquid. Fats and oils are made up of various types of triglycerides (triacylglycerols), which consist of three fatty acids attached to glycerol (Illustra-tion 1.4). The number of carbons contained in the fatty acid component of triglycerides varies from 8 to 22.
Fats and oils are a concentrated source of energy, providing 9 calories per gram. Fats perform a number of important functions in the body. They are precursors for cholesterol and sex-hormone synthesis, components of cell membranes, vehicles for carrying certain vitamins that are soluble in fats only, and suppliers of the essential fatty acids required for growth and health.
Essential Fatty Acids There are two essential fatty acids: linoleic acid and alpha-linolenic acid. Because these fatty acids are essential, they must be supplied in the diet. The central nervous system is particularly rich in derivatives of these two fatty acids. They are found in phospholipids, which—along with cholesterol—are the primary lipids in the brain and other nervous sys-tem tissue. Bio logically active derivatives of essential fatty acids include prostaglandins, thromboxanes, and prostacyclins.
Linoleic Acid Linoleic acid is the parent of the omega-6 (or n-6) fatty acid family. One of the major derivatives of linoleic acid is arachidonic acid. Arachidonic acid serves as a primary structural component of the central nervous system. Most vegetable oils, meats, and human milk are good sources of linoleic acid. American diets tend to Of the common types of amino acids, nine must be
pro-vided by the diet and are classified as “essential amino ac-ids.” (These are listed on page 3.) Many different amino acids obtained from food perform important functions, but since the body can manufacture these from other amino acids, they are classified as “nonessential amino acids.”
Food sources of pro-tein differ in quality, based on the types and amounts of amino acids they con-tain. Foods of high protein quality include a balanced assortment of all of the essential amino acids. Pro-tein from milk, cheese, meat, eggs, and other animal products is considered high quality. Plant sources of protein, with the exception of soybeans, do not pro-vide all nine essential amino acids. Combinations of plant foods, such as grains or seeds with dried beans, however, yield high-quality protein. Amino acids found in these individual foods
“complement” each other, thus providing a source of high-quality protein.
Recommended Protein Intake DRIs for protein are shown on the inside front cover of this text. In general, proteins should contrib-ute 10–35% of total energy intake.7 Protein deficiency, although rare in economically developed countries, leads to loss of muscle tissue, growth failure, weakness, reduced resistance to disease, kidney and heart problems, and contributes to the development of a severe form of protein-energy malnutrition known as kwashiorkor. Protein deficiency in adults produces a loss of body tissue protein, heart abnormalities, severe diarrhea, and other health problems.
Food Sources of Protein Animal products and dried beans are particularly good sources of protein. These and other food sources of proteins are listed in Table 1.6.
Fats (Lipids)
Fats in food share the property of being soluble in fats but not in water. They are actually a subcategory of lipids, but this category of macronutrient is referred to as fat in the DRIs.7 Lipids include fats, oils, and related compounds such as cholesterol. Fats are generally solid at room temperature, Kwashiorkor A severe form of
protein-energy malnutrition in young children. It is characterized by swelling, fatty liver, susceptibility to infection, profound apathy, and poor appetite. The cause of kwashiorkor is unclear.
Fatty Acids The fat-soluble components of fats in foods.
Glycerol A component of fats that is soluble in water. It is converted to glucose in the body.
Essential Fatty Acids Components of fat that are a required part of the diet (i.e., linoleic and alpha-linolenic acids). Both contain unsaturated fatty acids.
Prostaglandins A group of physiologically active substances derived from the essential fatty acids. They are present in many tissues and perform such functions as the constriction or dilation of blood vessels and stimulation of smooth muscles and the uterus.
Thromboxanes Biologically active substances produced in platelets that increase platelet aggregation (and therefore promote blood clotting), constrict blood vessels, and increase blood pressure.
Prostacyclins Biologically active substances produced by blood vessel walls that inhibit platelet aggregation (and therefore blood clotting), dilate blood vessels, and reduce blood pressure.
Table 1.6 Food sources of protein
Portion Size
Grams of Protein Meats
Beef, lean 3 oz 26
Tuna, in water 3 oz 24
Hamburger, lean 3 oz 24
Chicken, no skin 3 oz 24
Lamb 3 oz 22
Pork chop, lean 3 oz 20
Haddock, broiled 3 oz 19
Egg 1 med 6
Dairy Products
Cottage cheese, low fat 1⁄2c 14
Yogurt, low fat 1 c 13
Milk, skim 1 c 9
Milk, whole 1 c 8
Swiss cheese 1 oz 8
Cheddar cheese 1 oz 7
Grain Products
Oatmeal, cooked 1⁄2c 4
Pasta, cooked 1⁄2c 4
Bread 1 slice 2
Rice, white or brown 1⁄2c 2
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a fat is saturated or not depends on whether it has one or more double bonds between carbon atoms in one or more of the fatty acid compo-nents of the fat. If one double bond is present in one or more of the fatty acids, the fat is con-sidered monounsaturated; if two or more are present, the fat is polyunsaturated.
Some unsaturated fatty acids are highly unsaturated. Alpha-linolenic acid, for example, contains three double bonds, arachidonic acid four, EPA five, and DHA six. These fatty ac-ids are less stable than fatty acac-ids with fewer double bonds, because double bonds between atoms are weaker than single bonds.
Saturated fats contain no double bonds between carbons and tend to be solid at room temperature. Animal products such as butter, cheese, and meats and two plant oils (coco-nut and palm) are rich sources of saturated fats. Fat we consume in our diets, whether it contains primarily saturated or unsaturated fatty acids, is generally in the triglyceride (or triacylgly-cerol) form.
Fats (lipids) also come in these forms:
Monoglycerides (or monoacylglycerols), consisting
●
of glycerol plus one fatty acid
Diglycerides (or diacylglycerols), consisting of
●
glycerol and two fatty acids
Although most foods contain both saturated and unsaturated fats, animal foods tend to contain more sat urated and less unsaturated fat than plant foods.
Saturated fatty acids tend to increase blood levels of LDL cholesterol (the lipoprotein that increases heart-disease risk when present in high levels), whereas unsaturated fatty acids tend to decrease LDL-cholesterol levels.14 Hydrogenation and Trans Fats Oils can be made solid by adding hydrogen to the double bonds of their unsaturated fatty acids. This process, called hydrogenation, makes some of the fatty
acids in oils saturated a n d e n h a n c e s s t o r a g e life and baking qualities.
Hydrogenation may alter the molecular structure of the fatty acids, however, changing the naturally occurring cis structure to the trans form. Trans fatty acids raise blood LDL-cholesterol levels to a greater extent than do saturated fatty acids. Trans fatty acids are naturally present in dairy products and meats, but the primary provide sufficient to excessive levels of linoleic acid, and
considerable amounts are stored in body fat.
Alpha-Linolenic Acid Alpha-linolenic acid is the parent of the omega-3 (n-3) fatty acid family. It is present in many types of dark green vegetables, vegetable oils, and flaxseed. Derivatives of this essential fatty acid include eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Relatively little EPA and DHA are produced in the body from alpha-linolenic acid because the conversion process is slow.7 EPA and DHA also enter the body through intake of fatty, cold-water fish and shellfish and human milk. The EPA and DHA content of fish provide health benefits. Regular consumption of fish (two or more meals per week of fish) not only protects against irregular heartbeat, sudden death, and stroke but also reduces high blood pressure and plaque formation in arteries.10 DHA is found in large amounts in the central nervous system, the retina of the eye, and the testes. The body stores only small amounts of alpha-linolenic acid, EPA, and DHA.11
Increasing Omega-3 Fatty Acid Intake In the past it was thought that consuming high amounts of omega-6 fatty acids compared to omega-3 fatty acids could interfere with the availability of omega-3 fatty acids, particularly EPA and DHA. Although still somewhat controversial, it appears that rather high intakes of omega-6 fatty acids do not interfere with the availability of EPA and DHA.12 What interferes most with the availability of EPA and DHA for body functions is inadequate intake. On average, adults in the United States and Canada consume 100 mg EPA plus DHA daily, far short of the recommended intake of 500 mg daily.13
Saturated and Unsaturated Fats Fats (lipids) come in two basic types: saturated and unsaturated. Whether
Glycerol Fatty Acids
H
H C O C
O C H
H H
C H
H C H
H C H
H C H
H C H
H C H
H C H
H
H C O C
O C H
H C H
H C H
H C H
H C H
H C H
H C H
H
H C H
H
H C O C
O C H
H H
C H
H C H
H C H
H C H
H C H
H C H
H
H C H
H Illustration 1.4 Basic structure of a triglyceride.
Saturated Fats Fats in which adjacent carbons in the fatty acid component are linked by single bonds only (e.g., –C–C–C–C–).
Unsaturated Fats Fats in which adjacent carbons in one or more fatty acids are linked by one or more double bonds (e.g., –C–C=C–C=C–).
Monounsaturated Fats Fats in which only one pair of adjacent carbons in one or more of its fatty acids is linked by a double bond (e.g., –C–C=C–C–).
Polyunsaturated Fats Fats in which more than one pair of adjacent carbons in one or more of its fatty acids are linked by two or more double bonds (e.g., –C–C=C–C=C–).
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to weight gain. Current recommendations regarding fat intake do not encourage increased fat consumption, but rather emphasize that healthy diets include certain types of fat and that total caloric intake and physical activity are the most important components of weight management.7
Fats that elevate levels of LDL-cholesterol (which increases the risk of heart disease) are regarded as “unhealthful,” while those that lower LDL cholesterol and raise blood levels of HDL cholesterol (the one that helps the body get rid of cholesterol in the blood) are con-sidered healthful. The list of unhealthy fats includes trans fats, saturated fats, and cholesterol. Monounsaturated fats, polyunsaturated fats, alpha-linolenic acid, DHA, and EPA are considered healthful fats.
Current recommendations call for consumption of 20–35% of total calories from fat. The AIs for the essential fatty acid linoleic acid are set at 17 grams a day for men and 12 grams for women. AIs for the other essential fatty acid, alpha-linolenic acid, are 1.6 grams per day for men and 1.1 grams for women. It is recommended that people keep their intake of trans fats and saturated fats as low as possible while consuming a nutritionally adequate diet. Americans are being encouraged to increase consumption of EPA and DHA by eating fish more often.
They are being urged to reduce saturated fat intake in order to reduce the risk of heart disease.7
There is no recommended level of cholesterol intake, because there is no evidence that cholesterol is required in the diet. The body is able to produce enough cholesterol, and people do not develop a cholesterol deficiency dis-ease if it is not consumed. Because blood cholesterol levels tend to increase somewhat as consumption of cholesterol increases, it is recommended that intake should be mini-mal. Cholesterol intake averages around 237 mg per day in the United States, but a more health-promoting level of intake would be less than 200 mg a day.16
Food Sources of Fat The fat content of many foods can be identified by reading the nutrition information labels on food packages. The amount of total fat, saturated fat, trans fat, and cholesterol in a serving of food is listed dietary sources are products
made from hydrogenated fats. Due to new nutrition labeling requirements and public uproar, the trans f a t c o n t e n t o f b a k e r y products, chips, fast foods, and other products made with hydrogenated fats is decreasing.
Cholesterol Dietary cholesterol is a fatlike, clear liquid substance primarily found in lean and fat components of animal products. Cholesterol is a component of all ani-mal cell membranes, the brain, and the nerves. It is the precursor of estrogen, testosterone, and vitamin D, which is manufactured in the skin upon exposure to sunlight. The body generally produces only one-third of the cholesterol our bodies use, because more than sufficient amounts of cholesterol are provided in most people’s diet. The extent to which dietary cholesterol intake modifies blood choles-terol level appears to vary a good deal based on genetic tendencies.15 Dietary cholesterol intake affects blood cholesterol level substantially less than do saturated and trans fat intake, however.7 Leading sources of dietary cho-lesterol are egg yolks, meat, milk and milk products, and fats such as butter.
Recommended Intake of Fats Scientific evidence and opinions related to the effects of fat on health have changed substantially in recent years—and so have recommendations for fat intake. In the past, it was recom-mended that Americans aim for diets providing less than 30% of total calories from fat. Evidence indicating that the type of fat consumed is more important to health than is total fat intake has changed this advice. The watchwords for thinking about fat have become “not all fats are cre-ated equal: some are better for you than others.” Concerns that high-fat diets encourage the development of obesity have been eased by studies demonstrating that excessive caloric intakes—and not just diets high in fat—are related
Table 1.7 Food sources of fats
A. Total Fat
Portion Grams of Portion Grams of
Size Total Fat Size Total Fat
Fats and Oils
Mayonnaise 1 Tbsp 11.0
Ranch dressing 1 Tbsp 6.0
Vegetable oils 1 tsp 4.7
Butter 1 tsp 4.0
Margarine 1 tsp 4.0
Meats, Fish
Sausage 4 links 18.0
Hot dog 2 oz 17.0
Hamburger, 21% fat 3 oz 15.0
Hamburger, 16% fat 3 oz 13.5
Steak, rib-eye 3 oz 9.9
Bacon 3 strips 9.0
Steak, round 3 oz 5.2
Chicken, baked, no skin 3 oz 4.0
Flounder, baked 3 oz 1.0
Shrimp, boiled 3 oz 1.0
Trans fat A type of unsaturated fat present in hydrogenated oils, margarine, shortenings, pastries, and some cooking oils that increase the risk of heart disease. Fats containing fatty acids in the trans versus the more common cis form are generally referred to as trans fat.
Cholesterol A fat-soluble, colorless liquid primarily found in animals products.
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B. Saturated Fats
Portion Grams of Portion Grams of
Size Saturated Fat Size Saturated Fat
Fats and Oils
Margarine 1 tsp 2.9
Butter 1 tsp 2.4
Salad dressing, ranch 1 Tbsp 1.2
Peanut oil 1 tsp 0.9
Olive oil 1 tsp 0.7
Salad dressing, thousand island 1 Tbsp 0.5
Canola oil 1 tsp 0.3
Milk and Milk Products
Cheddar cheese 1 oz 5.9
American cheese 1 oz 5.5
Milk, whole 1 c 5.1
Cottage cheese, regular 1⁄2 c 3.0
Milk, 2% 1 c 2.9
Milk, 1% 1 c 1.5
Milk, skim 1 c 0.3
Meats, Fish
Hamburger, 21% fat 3 oz 6.7
Sausage, links 4 5.6
Hot dog 1 4.9
Chicken, fried, with skin 3 oz 3.8
Salami 3 oz 3.6
Haddock, breaded, fried 3 oz 3.0
Rabbit 3 oz 3.0
Pork chop, lean 3 oz 2.7
Steak, round, lean 3 oz 2.0
Turkey, roasted 3 oz 2.0
Chicken, baked, no skin 3 oz 1.7
Prime rib, lean 3 oz 1.3
Venison 3 oz 1.1
Tuna, in water 3 oz 0.4
Fast Foods
Croissant w/ egg, 1 16.0
bacon, & cheese
Sausage croissant 1 16.0
Whopper 1 11.0
Cheeseburger 1 9.0
Bac’n Cheddar Deluxe 1 8.7
Taco, regular 1 4.0
Chicken breast sandwich 1 3.0
Nuts and Seeds
Macadamia nuts 1 oz 3.2
Peanuts, dry-roasted 1 oz 1.9
Sunflower seeds 1 oz 1.6
Fast Foods
Whopper 8.9 oz 32.0
Big Mac 6.6 oz 31.4
Quarter Pounder with Cheese 6.8 oz 28.6
Veggie pita 1 17.0
Subway meatball sandwich 1 16.0
Subway turkey sandwich 1 4.0
Milk and Milk Products
Cheddar cheese 1 oz 9.5
Milk, whole 1 c 8.5
American cheese 1 oz 6.0
Cottage cheese, regular 1⁄2 c 5.1
Milk, 2% 1 c 5.0
Milk, 1% 1 c 2.9
Milk, skim 1 c 0.4
Yogurt, frozen 1 c 0.3
Other Foods
Avocado 1⁄2 15.0
Almonds 1 oz 15.0
Cashews 1 oz 13.2
French fries, small serving 1 10.0 Taco chips 1 oz (10 chips) 10.0 Potato chips 1 oz (14 chips) 7.0
Peanut butter 1 Tbsp 6.1
Egg 1 6.0
Table 1.7 Food sources of fats (continued)
A. Total Fat (Continued)
Portion Grams of Portion Grams of
Size Total Fat Size Total Fat
continued C. Unsaturated Fats
Portion Grams of Portion Grams of
Size Unsaturated Fat Size Unsaturated Fat
Fats and Oils
Canola oil 1 tsp 4.1
Vegetable oils 1 tsp 3.6
Margarine 1 tsp 2.9
Butter 1 tsp 1.3
Milk and Milk Products
Cottage cheese, regular 1⁄2 c 3.0
Cheddar cheese 1 oz 2.9
American cheese 1 oz 2.8
Milk, whole 1 c 2.8
Meats, Fish
Hamburger, 21% fat 3 oz 10.9
Haddock, breaded, fried 3 oz 6.5 Chicken, baked, no skin 3 oz 6.0
Pork chop, lean 3 oz 5.3
Turkey, roasted 3 oz 4.5
Tuna, in water 3 oz 0.7
Egg 1 5.0
Nuts and Seeds
Sunflower seeds 1 oz 16.6
Almonds 1 oz 12.6
Peanuts 1 oz 11.3
Cashews 1 oz 10.2
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Table 1.7 Food sources of fats (continued)
D. Trans Fats
Portion Grams Portion Grams
Size Trans Fats Size Trans Fats
E. Cholesterol
Portion Milligrams Portion Milligrams
Size Cholesterol Size Cholesterol
Fats and Oils
Butter 1 tsp 10.3
Vegetable oils, margarine 1 tsp 0 Meats, Fish
Brain 3 oz 1476
Liver 3 oz 470
Egg 1 212
Veal 3 oz 128
Shrimp 3 oz 107
Prime rib 3 oz 80
Chicken, baked, no skin 3 oz 75
Salmon, broiled 3 oz 74
Turkey, baked, no skin 3 oz 65
Hamburger, 20% fat 3 oz 64
Ostrich, ground 3 oz 63
Pork chop, lean 3 oz 60
Hamburger, l0% fat 3 oz 60
Venison 3 oz 48
Wild pig 3 oz 33
Goat, roasted 3 oz 32
Tuna, in water 3 oz 25
Milk and Milk Products
Ice cream, regular 1 c 56
Milk, whole 1 c 34
Milk, 2% 1 c 22
Yogurt, low fat 1 c 17
Milk, 1% 1 c 14
Milk, skim 1 c 7
F. Omega-3 (n-3) Fatty Acids
Portion Milligrams Portion Milligrams
Size EPA 1 DHA Size EPA 1 DHA
Fish and Seafood
Fish oil 1 tsp 2796
Shad 3.5 oz 2046
Salmon, farmed 3.5 oz 1825
Anchovies 3.5 oz 1747
Herring 3.5 oz 1712
Salmon, wild 3.5 oz 1564
Whitefish 3.5 oz 1370
Mackerel 3.5 oz 1023
Sardines 3.5 oz 840
Tilefish 3.5 oz 796
Whiting 3.5 oz 440
Flounder 3.5 oz 426
Trout, freshwater 3.5 oz 420
Oysters 3.5 oz 375
Snapper 3.5 oz 273
Shrimp 3.5 oz 268
Clams 3.5 oz 241
Haddock 3.5 oz 202
Catfish, wild 3.5 oz 201
Crawfish 3.5 oz 187
Sheapshead 3.5 oz 162
Tuna, light, and in oil 3.5 oz 109
Lobster 3.5 oz 71
Other
Egg yolk 1 40
DHA-fortified egg 1 150
Human milk 4.0 oz 126
DHA-fortified beverages 4 oz 32
*Mercury content <0.2 ppm as given in Mercury levels in commercial fish and shellfish, 2006 update, U.S. Environmental Protection Agency, www.epa.gov.
Fats and Oils
Margarine, stick 1 tsp 1.3
Margarine, tub (soft) 1 tsp 0.1
Shortening 1 tsp 0.3
Butter 1 tsp 0.1
Margarine, “no trans fat” 1 tsp 0 Meats
Beef 3 oz 0.5
Chicken 3 oz 0.1
Milk
Whole 1 c 0.2
Other Foods
Doughnut 1 3.2
Danish pastry 1 3.0
French fries, small serving 1 2.9
Cookies 2 1.8
Corn chips 1 oz 1.4
Cake 1 slice 1.0
Crackers 4 squares 0.5
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and E, and beta-carotene—a precursor of vitamin A) act as antioxidants and perform other functions. By preventing or repairing damage to cells due to oxidation, these vita-mins help maintain body tissues and prevent disease.
Primary functions, consequences of deficiency and overdose, primary food sources, and comments about each vitamin are listed in Table 1.9 starting on the next page.
Recommended Intake of Vitamins Recommenda-tions for levels of intake of vitamins are presented in the tables on the inside front covers of this text. Note that Tol-erable Upper Levels of Intake (ULs) for many vitamins are also given; they represent levels of intake that should not be exceeded. Table 1.10 (pages 19–21) lists food sources of each vitamin.
Other Substances in Food
“Things don’t happen by accident in nature.
If you observe it, it has a reason for being there.”
Norman Krinsky, Tufts University
There are many substances in foods in addition to nutrients that affect health. Some foods contain naturally occurring toxins, such as poison in puffer fish and solanine in green sections near the
skin of some potatoes. Con-suming the poison in puffer fish can be lethal; large doses of solanine can inter-fere with nerve impulses.
Some plant pigments, hor-mones, and other naturally occurring substances that protect plants from insects, oxidization, and other damaging exposures also appear to benefit human health. These substances in plants are referred to as phytochemicals, and knowledge about their ef-fects on human health is advancing rapidly. Many of
the phytochemicals that benefit health are pigments that act as antioxidants in the human body. Table 1.11 shows a list of the top food sources of antioxidants. Notice that most of the foods listed are colorful. That’s due to the antioxidant pigments they contain.
Consumption of foods rich in specific pigments and other phytochemicals, rather than con sump tion of isolated phytochemicals, may help prevent certain types of cancer, cataracts, type 2 diabetes, hypertension, infections, and heart disease. High intakes of certain phytochemicals from vegetables, fruits, nuts, seeds, and whole-grain products may partially account for lower rates of heart disease and cancer observed in people with high intakes of these foods.19,20 on the label. Table 1.7 lists the total fat, saturated fat,
unsaturated fat, trans fat, cholesterol, and omega-3–fatty acid contents (EPA and DHA) of selected foods.
Vitamins
Vitamins are chemical substances in foods that perform specific functions in the body. Fourteen have been dis-covered so far. They are classified as either fat soluble or water soluble (Table 1.8).
The B-complex vitamins and vitamin C are solu-ble in water and found dissolved in water in foods. The fat-soluble vitamins consist of vitamins A, D, E, and K and are present in the fat portions of foods. (To remember the fat-soluble vitamins, think of “DEKA” for vitamins D, E, K, and A.) Only these chemical substances are truly vita-mins. Substances such as coenzyme Q10, inositol, provitamin B5 complex, and pangamic acid (vitamin B15) may be called vitamins, but they are not. Except for vitamin B12, water-soluble vitamin stores in the body are limited and run out within a few weeks to a few months after intake becomes inadequate. Fat-soluble vitamins are stored in the body’s fat tissues and the liver. These stores can be sizable and last from months to years when intake is low.
Excessive consumption of the fat-soluble vitamins from supplements, especially of vitamins A and D, pro-duces various symptoms of toxicity. High intake of the water-soluble vitamins from supplements can also produce adverse health effects. Toxicity symptoms from water-soluble vitamins, however, tend to last a shorter time and are more quickly remedied. Vitamin overdoses are very rarely related to food intake.
Vitamins do not provide energy or, with the exception of choline, serve as structural components of the body.
Some play critical roles as coenzymes in chemical changes that take place in the body, known as metabolism. Vita-min A is needed to replace the cells that line the mouth and esophagus, thiamin is needed for maintenance of nor-mal appetite, and riboflavin and folate are needed for the synthesis of body proteins. Other vitamins (vitamins C
Table 1.8 Vitamin solubility Water-Soluble
Vitamins
Fat-Soluble Vitamins B-complex vitamins Vitamin A (retinol,
Thiamin (B1) beta-carotene)
Riboflavin (B2) Vitamin D (1,25
Niacin (B3)
Vitamin B6 cholecalciferol)
Folate Vitamin E
Vitamin B12 (alpha-tocopherol)
Biotin Vitamin K
Pantothenic acid Choline
Vitamin C (ascorbic acid)
Coenzymes Chemical substances that activate enzymes.
Metabolism The chemical changes that take place in the body. The conversion of glucose to energy or body fat is an example of a metabolic process.
Antioxidants Chemical substances that prevent or repair damage to cells caused by exposure to oxidizing agents such as oxygen, ozone, and smoke and to other oxidizing agents normally produced in the body. Many different antioxidants are found in foods;
some are made by the body.
Phytochemicals (phyto = plants) Chemical substances in plants, some of which affect body processes in humans that may benefit health.
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