Chapter 10 Reading - Vitamins that are Important for your Body PDF

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Notes on vitamins needs in your body to function and precursors...

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Reading 10.1 - Vitamins: organic, essential nutrients required in small amounts by the body for health. Vitamins regulate body processes that support growth and maintain life. - Amine: containing nitrogen (the first vitamins discovered contained nitrogen) - The vitamins are a diverse group of essential nutrients that regulate most body processes involved in supporting growth and maintaining life. - Notably, the vitamins differ from carbohydrates, fats, and proteins in the following ways: - Structure. Vitamins are individual units; they are not linked together (as are molecules of glucose or amino acids). Appendix C presents the chemical structure for each of the vitamins. - Function. Vitamins do not yield energy when metabolized; many of them do, however, assist the enzymes that participate in the release of energy from carbohydrates, fats, and proteins. - Food contents. Like carbohydrates, fats, and proteins, vitamins are readily available from foods, but the amounts of vitamins people ingest from foods and the amounts they require daily are measured in micrograms (μg) or mil-ligrams (mg), rather than grams (g).* For this reason, the vitamins are some-times described as micronutrients. - Bioavailability: the rate at and the extent to which a nutrient is absorbed and used - Precursors: substances that precede others; with regard to vitamins, compounds that can be converted into active vitamins; also known as provitamin - Carbohydrates and proteins are hydrophilic and lipids are hydrophobic - B vitamins and vitamin C are hydrophilic and water soluble - This includes thiamin, riboflavin, niacin, biotin, pantothenic acid, vitamin B6, folate, and vitamin B12 - Vitamin A, D, E, and K are hydrophobic and fat-soluble - Solubility is apparent in the food sources of the different vitamins, and it affects their absorption, transport, storage, and excretion by the body - The water-soluble vitamins are found in the watery compartments of foods; the fat-soluble vitamins usually occur together in the fats and oils of foods. On being absorbed, the water-soluble vitamins move directly into the blood. Like fats, the fat-soluble vitamins must first enter the lymph, then the blood. Once in the blood, many of the water-soluble vitamins travel freely, whereas many of the fat-soluble vitamins require transport proteins. Upon reaching the cells, water-soluble vitamins freely circulate in the water-filled compartments whereas fat-soluble vitamins are held in fatty tissues and the liver until needed. The kidneys, monitoring the blood that flows through them, detect and remove small excesses of water-soluble vitamins; large excesses, however, may overwhelm the system, creating adverse effects. Fat-soluble vitamins tend to remain in fat-storage sites in the body rather than being excreted, and so are more likely to reach toxic levels when consumed in excess. - Because the body stores fat-soluble vitamins, they can be eaten in large amounts once in a while and still meet the body’s needs over time. Water-soluble vitamins

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are retained in the body for varying lengths of time. The water-soluble vitamins must be eaten more regularly than the fat-soluble vitamins, although a single day’s omission from the diet does not create a deficiency. Some water-soluble vitamins are synthesized by GI tract bacteria and absorbed by the large intestine, but not in quantities great enough to meet the body’s needs; foods must supply these essential nutrients Determining the bioavailability of a vitamin is a more complex task because it depends on many factors, including: - Efficiency of digestion and time of transit through the GI tract - Previous nutrient intake and nutrition status - Method of food preparation (raw, cooked, or processed) - Source of the nutrient (synthetic, fortified, or naturally occurring) - Other foods consumed at the same time Fresh foods naturally contain vitamins, but because these vitamins are organic, they can be readily destroyed during processing - Prolonged heating may destroy much of the thiamin in food - Because riboflavin can be destroyed by the ultraviolet rays of the sun or by fluorescent light, foods stored in transparent glass containers are most likely to lose riboflavin - Oxygen destroys vitamin C, so losses occur when foods are cut, processed, and stored Coenzymes: complex organic molecules that work with enzymes to facilitate the enzymes’ activity. Many coenzymes have B vitamins as part of their structures. - Thiamin, riboflavin, niacin, pantothenic acid, and biotin form part of the coenzymes that assist enzymes in the release of energy from carbohydrate, fat, and protein The energy-yielding nutrients-- carbohydrate, fat, and protein-- are use for fuel; the B vitamins help the body to use that fuel Without its coenzyme, an enzyme cannot function Thiamin: a B vitamin. The coenzyme form is TPP (thiamin pyrophosphate). The TPP coenzyme participates in the conversion of pyruvate to acetyl CoA The thiamin RDA is based primarily on its role in enzyme activity - Generally, thiamin needs will be met if a person eats enough food to meet energy needs—if that energy comes from nutritious foods. Inadequate thiamin intakes have been reported among the nation’s malnourished and homeless people - People who derive most of their energy from empty-kcalorie foods and beverages risk thiamin deficiency. Alcohol provides a good example of how empty kcalories can lead to thiamin deficiency. Alcohol con-tributes energy but provides few, if any, nutrients and often displaces food. - ⅘ alcoholics are thiamin deficient, which damages the brain’s structure and impairs its function

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Berberi: the thiamin-deficiency disease characterized by muscle weakness, edma, or both - First discovered in Indonesia when the custom of polishing rice became widespread - Rice was 80% of the energy intake of the people of that area, and the germ and bran of the rice grain was their principal source of thiamin - Dry beriberi: damage to the nervous system and is characterized by muscle weakness in the arms and legs - Wet beriberi: damage to the cardiovascular system and is characterized by dilated blood vessels, which cause the heart to work harder and the kidneys to retain salt and water, resulting in edema - Typically both types appear together, with one set of symptoms predominating Thiamin leaches into water when foods are boiled or blanched. Cooking methods that require little or no water such as steaming and microwave heating conserve thiamin and other water-soluble vitamins. Riboflavin: a B vitamin. The coenzyme form are FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide) - Riboflavin’s RDA is based primarily on its role in enzyme activity - Lack of riboflavin causes inflammation of the membranes of the mouth, skin, eyes, and GI tract. - Greatest contributions of riboflavin come from milk and milk product - Whole-grain or enriched grains are also valuable sources because of the quantities people typically con-sume. When riboflavin sources are ranked by nutrient density (per kcalorie), many dark green, leafy vegetables (such as broccoli, turnip greens, asparagus, and spinach) appear high on the list. Vegans and others who don’t use milk must rely on ample servings of dark greens and enriched grains for riboflavin. - Ultraviolet light destroys riboflavin - Stable to heat, so cooking doesn’t destroy it Niacin: a B vitamin. The coenzyme forms are NAD (nicotinamide adenine dinucleotide) and NADP (the phosphate form of NAD). Niacin can be eaten preformed or made in the body from its precursor, tryptophan, an essential amino acid. - Niacin is unique among the B vitamins in that the body can make it from the amino acid tryptophan. - A food containing 1 milligram of niacin and 60 milligrams of tryptophan provides the equivalent of 2 milligrams of niacin, or 2 niacin equivalents. Niacin equivalents (NE): the amount of niacin present in food, including the niacin that can theoretically be made from its precursor, tryptophan, present in the food. - 1 NE = 1 mg niacin or 60 mg tryptophan Pellagra: the niacin-deficiency disease, characterized by diarrhea, dermatitis, dementia, and eventually death.

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Produces the symp-toms of diarrhea, dermatitis, dementia, and eventually death (often called “the four Ds”). - In the early 1900s, pellagra caused widespread misery and some 87,000 deaths in the US South, where many people subsisted on a low-protein diet centered on corn. This diet supplied neither enough niacin nor enough tryptophan. Niacin flush: a temporary burning, tingling, and itching sensation that occurs when a person takes a large dose of nicotinic acid; often accompanied by a headache and reddened face, arms, and chest. - When a large dose (levels commonly available only from supplements) overwhelms the body and raises blood concentrations to abnormally high levels, the nutrient is acting like a drug and having a pharmacological effect Meat, poultry, fish, legumes, and enriched and whole grains contribute about half the niacin people consume. Mushrooms, potatoes, and tomatoes are among the richest vegetable sources, and they can provide abundant niacin when eaten in generous amounts Niacin is less vulnerable to losses during food preparation and storage than other water-soluble vitamins. Being fairly heat resistant, niacin can withstand reasonable cooking times, but like other water-soluble vitamins, it will leach into cooking water. Biotin: a B vitamin that functions as a coenzyme in metabolism. - Biotin delivers a carbon to 2-carbon pyruvate, which replenishes oxaloacetate, the 4-carbon compound needed to combine with acetyl CoA to keep the TCA cycle turning The biotin coenzyme also participates in gluconeogenesis, fatty acid synthesis, and the breakdown of certain fatty acids and amino acids - Very rare deficiencies - Researchers can induce a biotin deficiency in animals or human beings by feeding them raw egg whites, which contain a protein that binds biotin and thus prevents its absorption. Biotin-deficiency symptoms include skin rash, hair loss, and neurological impairment. - Biotin is widespread in foods (including egg yolks), so eat-ing a variety of foods protects against deficiencies. Some biotin is also synthe-sized by GI tract bacteria, but this amount does not contribute much to the biotin absorbed. Pantothenic acid: a B vitamin. The principal active form is part of coenzyme A. - Rare deficiency - Its symptoms involve a general failure of all the body’s systems and include fatigue, GI distress, and neurological disturbances. The “burning feet” syndrome that af-fected prisoners of war in Asia during World War II is thought to have been caused by pantothenic acid deficiency - Beef, poultry, whole grains, potatoes, tomatoes, and broccoli are good sources - Losses of pantothenic acid during food production can be substantial because it is readily destroyed by the freezing, canning, and refining processes. Vitamin B6: a family of compounds—pyridoxal, pyridoxine, and pyridoxamine. The primary active coenzyme form is PLP (pyridoxal phosphate).

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The RDA for vitamin B6 is based on the amounts needed to maintain adequate levels of its coenzymes. Unlike other water-soluble vitamins, vitamin B6 is stored extensively in muscle tissue. - Without adequate vitamin B6, synthesis of key neurotrans-mitters diminishes, and abnormal compounds produced during tryptophan me-tabolism accumulate in the brain. Early symptoms of vitamin B6 deficiency include depression and confusion; advanced symptoms include abnormal brain wave pat-terns and convulsions. Alcohol contributes to the destruction and loss of vitamin B6 from the body. - When the body breaks down alcohol, it produces acetalde-hyde. If allowed to accumulate, acetaldehyde dislodges the PLP coenzyme from its enzymes; once loose, PLP breaks down and is excreted - Meats, fish, and poultry, potatoes and a few other vegetables, and fruits offer vitamin B6 Folate: a B vitamin; also known as folic acid, folacin, or pteroylglutamic acid (PGA). The coenzyme forms are DHF and THF. - Its primary coenzyme form, THF (tetrahydrofolate), serves as part of an enzyme complex that transfers 1-carbon compounds that arise during metabolism. - Thus a person consuming 100 micrograms of folate from foods and 100 micrograms from a supplement receives 270 dietary folate equivalents (DFE). The need for folate rises considerably during pregnancy and whenever cells are multiplying, so the recommendations for pregnant women are considerably higher than for other adults - All women of childbearing age who are capable of becoming pregnant should consume 0.4 milligram (400 micrograms) of folate daily—easily accomplished by eating folate-rich foods, folate-fortified foods, or a multivitamin supplement daily. - Without folate, homocysteine accumulates, which seems to enhance formation of blood clots and atherosclerotic lesions. Fortified foods and folate supplements raise blood folate and reduce blood homocysteine, but may not reduce the risk of heart attacks, strokes, or death from cardiovascular causes. - In a folate deficiency, the replacement of red blood cells and GI tract cells falters - Anemia: literally, “too little blood;” any condition in which there is reduced delivery of oxygen to the tissues. Anemia is not a disease itself but can be a consequence of many different disease conditions, including some nutrient deficiencies - Folate is especially abundant in le-gumes, fruits, and vegetables. The vitamin’s name suggests the word foliage, and indeed, dark green, leafy vegetables are outstanding sources. With fortification, grain products also contribute folate. Meats and milk products are poor folate sources. Heat and oxidation during cooking and storage can destroy as much as half of the folate in foods. Dietary folate equivalents (DFE): the amount of folate available to the body from naturally occurring sources, fortified foods, and supplements, accounting for differences in the bioavailability from each source

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Neural tube: the embryonic tissue that forms the brain and spinal cord. Neural tube defects: malformations of the brain, spinal cord, or both during embryonic development that often result in lifelong disability or death. The two main types of neural tube defects are spina bifida (literally “split spine”) and anencephaly (“no brain”). Vitamin B12: a B vitamin characterized by the presence of cobalt. The active forms of coenzyme B12 are methylcobalamin and deoxyadenosylcobalamin. - Vitamin B12 maintains the sheath that surrounds and protects nerve fibers and promotes their normal growth. Bone cell activity and metabolism also depend on vitamin B12 - Vitamin B12 enters the enterohepatic circulation - The RDA for adults is only 2.4 micrograms of vitamin B12 a day—just over two-millionths of a gram. As tiny as this amount appears to the human eye, it contains billions of molecules of vitamin B12, enough to provide coenzymes for all the enzymes that need its help. - Vitamin B12 deficiency is common among adults who use heartburn medica-tions to suppress gastric acid production. Deficiency is also common among the elderly. Many older adults develop atrophic gastritis, a condition that damages the cells of the stomach. - Because vitamin B12 is found primarily in foods derived from animals, vegetarians, and especially vegans, are especially likely to develop a vitamin B12 deficiency. It may take several years for people who stop eating animal-derived foods to develop deficiency symptoms because the body recycles much of its vitamin B12, reabsorbing it over and over again and conserving its supply. - Also can impair memory and cognition - Vitamin B12 is unique among the vitamins in being found almost exclusively in foods derived from animals. Its bioavailability is greatest from milk and fish. - Vegans, who restrict all foods derived from animals, need a reliable source, such as vitamin B12–fortified soy milk or vitamin B12 supplements. Intrinsic factor: a glycoprotein (a protein with short polysaccharide chains attached) secreted by the stomach cells that binds with vitamin B12 in the small intestine to aid in the absorption of vitamin B12. Atrophic gastritis: chronic inflammation of the stomach accompanied by a diminished size and functioning of the mucous membranes and glands. This condition is also characterized by inadequate hydrochloric acid and intrinsic factor—two substances needed for vitamin B12 absorption. Pernicious anemia: a macrocytic anemia that reflects a vitamin B12 deficiency caused by lack of intrinsic factor and characterized by abnormally large and immature red blood cells. Other symptoms include muscle weakness and irreversible neurological damage. Choline is not defined as a vitamin, but it is an essential nutrient that is commonly grouped with the B vitamins - The body uses choline to make the neurotransmitter acetylcholine and the phospholipid lecithin. During pregnancy, choline supports the neurological development of the fetus, and during adult-hood, choline may improve cognition.

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The body can make choline from the amino acid me-thionine, but synthesis alone is insufficient to fully meet the body’s needs; dietary choline is also needed. - Can be found in common foods such as milk, eggs, and peanuts - Also a part of lecithin Inositol: a nonessential nutrient that can be made in the body from glucose. Inositol is a part of cell membrane structures. Carnitine: a nonessential, nonprotein amino acid made in the body from lysine that helps transport fatty acids across the mitochondrial membrane. Vitamin B5 is another name for pantothenic acid

Scurvy: the vitamin C–deficiency disease. Antiscorbutic factor: the original name for vitamin C. Ascorbic acid: one of the two active forms of vitamin C. Many people refer to vitamin C by this name. Cofactor: a small, inorganic or organic substance that facilitates the action of an enzyme. Antioxidants: in the body, substances that significantly decrease the adverse effects of free radicals on normal physiological functions. Free radical: an unstable molecule with one or more unpaired electrons.oxidative stress: a condition in which the production of oxidants and free radicals exceeds the body’s ability to handle them and prevent damage. Collagen: the structural protein from which connective tissues such as scars, tendons, ligaments, and the foundations of bones and teeth are made. In the cells and body fluids, vitamin C protects tissues from the oxidative stress of free radicals and thus may play an impor-tant role in preventing diseases. In the small intestine, vitamin C enhances iron absorption by protecting iron from oxidation. Vitamin C helps to form collagen As in collagen formation, vitamin C helps in the hydroxylation of carnitine, a compound that transports fatty acids, especially long-chain fatty acids, across the inner membrane of mitochondria in cells - Also participates in the conversions of the amino acids tryptophan and tyrosine to the neurotransmitters serotonin and norepinephrine, respectively. Vitamin C also as-sists in the making of hormones, including thyroxine, which regulates the meta-bolic rate; when metabolism speeds up in times of extreme physical stress, the body’s use of vitamin C increases. Histamine: a substance produced by cells of the immune system as part of a local immune reaction to an antigen It’s recommended to take 10 mg of vitamin C daily For smokers they need an additional 35 mg (45 mg total) False positive: a test result indicating that a condition is present (positive) when in fact it is not present (therefore false).

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False negative: a test result indicating that a condition is not present (negative) when in fact it is present (therefore false). When vitamin C con...