The Encyclopedia Of Nutrition And Good Health - V docx

V 639 valerian root (Valerian officinalis; garden helio- trope; setwall) The root of a perennial herb native to Europe, North America, and northern Asia that has been used as a sleep aid and antianxiety treat- ment for more than 1,000 years. The plant is inconspicuous except for its small white or pink flowers and an unusual odor that some have described as reminiscent of aged cheese. According to legend, the Pied Piper used valerian to lure rats from the village of Hamelin. Valerian is a popular dietary supplement in the United States and in Europe whose supporters claim it has a calming effect and can induce sleep. Reliable research to support these claims does not yet exist, but the herb does appear to have some effect on the neurotransmitter gamma- aminobutyric acid (GABA). Small studies suggest effectiveness in promoting sleep compared to placebo. People with nerve disorders that causes uncontrollable spasms or who suffer from TARDIVE DYSKINESIA have been found to have low levels of GABA in their brains. Because of the herb’s repu- tation as an antispasmodic, it has been used for centuries by women seeking relief from menstrual cramps. As a food, valerian is classified “generally recognized as safe.” Because valerian root is available in the United States as an herb, its safety and efficacy have not been tested by the U.S. Food and Drug Administra- tion ( FDA). However, in high doses valerian root rarely can cause liver damage with long-term use or high doses. Some patients who have taken the supplements have suffered chest pain, heart arrhythmia, tremors, insomnia, headache, and blurred vision. With long-term high doses, sud- denly stopping valerian may be associated with a withdrawal syndrome. A few reports suggest possi- ble decreased alertness after valerian use. Women who are pregnant or nursing should not take this supplement due to inadequate safety data. Garges, P. et al. “Cardiac Complications and Delirium Associated with Valerian Root Withdrawal,” Journal of the American Medical Association 280 (November 1998): 1,566–1,567. valine (Val, L-valine) A dietary essential AMINO ACID that serves as an important protein building block. Valine is classified as a BRANCHED CHAIN AMINO ACID , along with ISOLEUCINE and LEUCINE. The daily requirement for valine is estimated to be 10 mg per kilograms of body weight, similar to the other branched chain amino acids. Infused branched chain amino acids are selectively used for energy by skeletal muscle rather than by the LIVER. Branched chain amino acids may help restore mus- cles in patients with liver disease or in patients who have undergone physical trauma such as surgery. However, it is not established that these amino acids have an anabolic (muscle enhancing) effect when used as supplements for healthy people. Valine and other branched chain amino acids are useful in treating liver damage associated with ALCOHOLISM (hepatic encephalopathy). They seem to limit muscle wasting and reduce some of the neurologic effects related to this disease. Valine and branched chain amino acids may be useful in treat- ing amyotrophic lateral sclerosis (Lou Gehrig’s dis- ease). Levels of these amino acids are low in these patients. On the other hand, animal studies indi- cate that an excess of one branched chain amino acid antagonizes the other two. (See also AMINO ACID METABOLISM .) vanadium A TRACE MINERAL required by animals for normal growth and development. Deprivation of this element causes slowed growth, reproductive problems and blood abnormalities in rats and chicks. Vanadium in the form of vanadate and vanadyl sulfate improves the effect of insulin in diabetic animals; and artificially induced diabetes in rats can be reversed by vanadate. Large doses also affect serum FAT and CHOLESTEROL levels, although more research in this area is needed. There is no RECOMMENDED DIETARY ALLOWANCE for vanadium, and the amounts required for opti- mal health are unknown. Nutritional requirements would likely be met by levels present in food. Black pepper and dill seeds are the richest sources. Whole grains, seafood, milk products, and meat are fair sources, while beverages, vegetables, and fruits contain the lowest amounts. The average daily intake in the United States is about 20 mcg, quite low in comparison to known essential trace ele- ments. Elevated vanadium is associated with bipo- lar disorder, and high levels of vanadium may be toxic. vanilla (Vanilla planifolia) A tropical plant that produces pods containing vanilla, an aromatic ingredient used as a food flavoring. Vanilla is a member of a group of tropical orchids, native to Central America and Mexico. The active ingredi- ent, ethyl vanillin, is chemically synthesized and marketed as “vanillin.” Ethyl vanillin has 3.5 times the flavor intensity of vanilla bean extract. Because it lacks minor ingredients found in the extract, the taste is not identical. Vanilla is used to flavor ice cream, beverages, chocolate, candy, and gelatin. Vanilla is considered a safe additive. (See also FLA- VORS ; FOOD ADDITIVES.) variant Creutzfeldt-Jakob disease (vCJD) See BEEF. varicose veins Bulging, sinuous veins that are close to the surface of the skin. Usually the term varicose veins refers to distended leg veins in which blood vessels become weakened, permitting blood to flow backward instead of forward to the heart. This condition affects an estimated 25 percent of American women, 10 percent of men, and 50 per- cent of people over the age of 50. Often, varicose veins are only a cosmetic issue with no symptoms. However, symptoms like aching legs can develop after a person has been standing for a long time. Leg cramps, swollen ankles, intense pain or tender- ness along the vein at the end of the day can occur. Occupations that require extended periods of standing increase the risk of varicose leg veins. Pregnancy also increases venous pressure in the legs and may lead to the development of varicose veins. Standing places heavy pressure against leg veins, and the extra weight of the blood stretches the walls of the vessels, which pulls apart vessel valves, causing blood to pool in the veins. This pressure can cause surface vein walls to bulge out into varicose veins. Varicose veins can occur anywhere in the body. Hemorrhoids are a common example; they can be aggravated in straining during bowel movements because intense abdominal pressure is transmitted to all veins, even leg veins. Defective, deeper veins can become inflamed (phlebitis) and create a blood clot, resulting in a more serious condition. If the clot dislodges, it can cause blockage in vessels of the lung, the heart ( HEART ATTACK or myocardial infarc- tion), or the brain ( STROKE). In addition to inheritance, lifestyle and diet are believed to be predominant factors in the develop- ment of varicose veins. They seldom occur in pop- ulations relying on a diet high in unrefined, fiber-rich foods. EXERCISE such as walking and bike riding contract leg muscles that push blood along the venous system. Increasing the strength of ves- sel walls may minimize the risk of varicose veins. Blue-red berry pigments called anthocyanidins and proanthocyanins can strengthen vessel walls, reduce capillary fragility and help protect the venous connective tissue. BLACKBERRIES, CHERRIES, and BLUEBERRIES are rich sources. People who have varicose veins may also be less able to break down FIBRIN, a clotting protein that is often deposited near varicose veins and increases the risk of clot formation. CAPSICUM (cayenne pepper), GINGER, GARLIC, and ONIONS increase fibrin breakdown. (See also CIRCULATORY SYSTEM; DIET, HIGH COMPLEX CAR- BOHYDRATE; FIBER.) vasoconstriction Reducing the diameter of blood vessels. Both environmental and physio- 640 vanilla logic factors can constrict vessels. For example, a drop in temperature causes vasoconstriction, an adaptation that helps conserve body heat. All blood vessels except capillaries and venules are regulated by the NERVOUS SYSTEM. Thus fear and other emotions can reduce blood flow. At wound sites, SEROTONIN and other products are liberated by blood PLATELETS, cells that stick to the walls of damaged vessels to form clots. Serotonin helps reduce blood loss by acting as a vasoconstrictor. Certain hormones act as vasoconstrictors: EPINEPH- RINE and norepinephrine (released by the ADRENAL GLANDS in response to stress) and ANGIOTENSIN II (formed in the KIDNEYS in response to a drop in blood pressure). vasodilation Increasing the diameter of blood vessels. Vasodilation increases blood flow and removes waste products while replenishing oxygen and nutrients. Decreased oxygen concentration and the accumulation of metabolic waste products help expand blood vessel walls. The accumulation of LACTIC ACID, decreased pH (more acidic blood), the buildup of carbon dioxide, and increased blood ion concentration (osmolarity) dilate blood vessels. Increased body temperature exerts a vasodilator effect to help cool the body. During inflammation, HISTAMINE is released from damaged cells and from immune cells called mast cells. Histamine is known to increase capillary leakiness, and fluid leakage out of capillaries accounts for swelling in areas of inflammation. An important family of vasodilators is the kinins, which represent peptides, whose parents occur in the blood and in tissues. Kinins resemble histamine: They relax the smooth muscles around vessels and increase capillary leakiness and blood flow through the kidneys. Kinins occur in sweat glands, salivary glands, and the PANCREAS. Kinin release is inhibited by GLUCOCORTICOIDS, hormones produced by the adrenal glands. A high protein diet also increases blood flow in the kidneys. PROS- TAGLANDINS, hormone-like substances made from essential fatty acids, can have similar effects. (See also EDEMA; NITRIC OXIDE.) vasopressin See ANTIDIURETIC HORMONE. veal BEEF from male dairy calves, ranging in age from four to 18 weeks. Subtherapeutic doses of drugs may be used when veal calves are very young; this treatment is discontinued as the animal’s immune system matures. Veal, like most red MEAT, is a good source of ZINC and other trace minerals. The nutrient content of a 3-oz. (85 g) braised veal cutlet is: 185 calories; protein, 23 g; fat, 9.4 g; cho- lesterol, 109 mg; calcium, 9 mg; iron, 0.8 mg; thi- amin, 0.06 mg; riboflavin, 0.21 mg; niacin, 4.6 mg. vegan See VEGETARIAN. vegetable oil Edible oil extracted from seeds or nuts. Plant oils provide ENERGY, VITAMIN E, and polyunsaturated FATTY ACIDS. No vegetable oil con- tains CHOLESTEROL because plants do not synthesize it. Vegetable oils classified as TRIGLYCERIDES; like animal FAT, they contain three fatty acids and GLYC- EROL (glycerin) and contain just as many calories as animal fat (nine calories per gram). Vegetable oils fall into three classes: saturated, monounsaturated, and polyunsaturated: 1. Saturated vegetable oils are solid at room tem- perature. The so-called TROPICAL OILS, palm ker- nel oil and COCONUT OIL , and VEGETABLE SHORTENING , a chemically hardened vegetable fat, are saturated and are solids at room temper- atures. These saturated fats resemble saturated animal fat, as in LARD, BUTTERFAT, and beef TAL- LOW . The excessive consumption of SATURATED FAT regardless of its source is believed to increase the risk of CARDIOVASCULAR DISEASE. 2. Monounsaturated oils including OLIVE OIL are rich in a fatty acid called OLEIC ACID, which lacks two hydrogen atoms and contains a single dou- ble bond. Olive oil apparently lowers blood LOW-DENSITY LIPOPROTEIN (LDL) cholesterol, the less desirable form, without lowering the “good” kind of cholesterol HIGH-DENSITY LIPOPROTEIN (HDL), and probably lowers the risk of cardio- vascular disease. 3. Polyunsaturated oils such as CORN OIL, SAF- FLOWER oil, SUNFLOWER oil, and SOYBEAN oil con- tain a preponderance of polyunsaturated fatty acids. These fat building blocks lack many hydrogen atoms and contain two or more dou- vegetable oil 641 ble bonds. High consumption of polyunsatu- rated vegetables oils apparently lowers LDL cho- lesterol levels, a desirable result, but also lowers HDL levels, which is undesirable. High con- sumption of polyunsaturated oils increases the need for the antioxidant vitamin E. Extraction of Oils The first step in oil extraction involves crushing or grinding oil-bearing tissue to release oil from cells. The second step involves pressing to squeeze oil from crushed tissue. Residues from pressing are usually extracted with solvents such as hexane to remove the remaining oil. The solvent is then removed. To purify these oils, they are further extracted with alkali and heated, degummed, deodorized by steam treatment, and decolorized by treatment with charcoal or clay. Since these proce- dures remove or destroy vitamin E, synthetic antioxidants like BHT, BHA, and PROPYL GALLATE are often added to retard RANCIDITY. Oils may be “win- terized” by removing particulate matter that form upon chilling. The assumption that cold-pressed oils have been extracted from the seeds under mild conditions and contain more vitamin E and polyunsaturated fatty acids may not be valid. Cold-pressed oils are often heated between 120° F and 150° F, then refined, bleached, and deodorized, processes that can involve further heating, possibly at temperatures as high as 450° F. Certain “unrefined oils” are available. In the preparation of these oils, processors do nothing to the oils after heating ground seeds and pressing them to extract the oils. Because such oils are less pure, they have distinctive flavors and colors. Hydrogenation Unsaturated vegetable oils can be hardened and stabilized by chemically adding hydrogen atoms to reduce the degree of polyunsaturation. Hydrogena- tion increases the shelf-life of an oil by making it more resistant to rancidity. Heating vegetable oils at high temperatures does not hydrogenate oils, nor does it convert them to saturated fat. “Partially hydrogenated” vegetable oils retain some of their polyunsaturated fatty acids and remain oils at room temperature, while completely hydrogenated (sat- urated) oils are solid at room temperature (veg- etable shortening). Hydrogenated vegetable oils as well as partially hydrogenated oils contain chemi- cally altered fatty acids called TRANS-FATTY ACIDS; their long-term safety has been questioned. Americans generally consume too much fat and oil, which increases the risk of HEART ATTACK , STROKE , OBESITY, and certain forms of CANCER.A person with high blood cholesterol may be advised to reduce saturated fat intake. Total fat should account for less than 30 percent of daily calories, perhaps as low as 20 percent of calories according to some authorities. To reduce the decomposition and rancidity of vegetable oils, store oils in the refrigerator in sealed dark containers. Do not heat oils any more than is necessary and limit cooking with oils at high temperatures. Discard cooking oils after use. vegetables Cultivated plants that generally pro- vide leaves, stems, roots, and flowers used as foods. Leafy vegetables include SPINACH, CHARD, CABBAGE, and LETTUCE. Stem vegetables are CELERY and ASPARAGUS; BEETS, TURNIPS, YAMS, POTATOES, and CARROTS are roots and tubers as opposed to stems. Vegetables like pumpkin, squash, BROCCOLI, and CAULIFLOWER are flowers. GARLIC and ONIONS are bulbs. Corn is a seed vegetable. Vegetables include several botanical classes, including TOMATOES (fruit); PEAS and BEANS (legumes); and MUSHROOMS ( FUNGI). Most regions of the world have contributed veg- etables, as indicated by the following examples: • Europe, the origin of beets, broccoli, BRUSSELS SPROUTS , cabbage, CHIVE, MUSTARD GREEN, pea, and turnip; the Mediterranean region: ARTI- CHOKE , asparagus, celery, chard, CHICKPEA, ENDIVE, KALE, KOHLRABI, OLIVE, PARSLEY, PARSNIP. • Africa: the BROAD BEAN, CRESS, OKRA, yam; the Middle East: broad bean, cabbage, carrot, cauli- flower, CUCUMBER, LENTIL, lettuce, mustard green, RADISH, SPINACH • India: EGGPLANT, MUNG BEAN; China: Chinese cabbage, SOYBEAN, water chestnut • Central Asia: beet, chive, carrot, DANDELION, gar- lic, LEEK, onion, pea, shallot, turnip • Central America: bean, corn, jicama, green PEP- PER, PUMPKIN, SQUASH, SWEET POTATO, tomato 642 vegetables • South America: cassava, corn, lima bean, pepper potato, sweet potato, tomato Root vegetables and tubers like yams, sweet potatoes, carrots, and potatoes are by far the lead- ing vegetable crops. They provide starch, fiber, minerals, and some vitamins. Orange-colored veg- etables like sweet potato and carrot provide BETA- CAROTENE. Several of the most popular vegetables in the United States provide minimal nutrient con- tent: celery, lettuce, cucumbers. The greener the vegetable, the more the beta-carotene (provitamin A) and CAROTENOIDS it contains. Spinach, collard greens, dandelion greens, kale, and Swiss chard are excellent sources and they provide vitamin C, iron, and calcium. The consumption of fresh vegetables in the United States has steadily increased since 1980 from about 115 lb. per person per year to over 190 lb. per year (1990). Nonetheless, fewer than 10 percent to 20 percent of U.S. citizens report eating the minimum recommended five daily servings of vegetables and fruits. Potatoes represent nearly 37 percent of all fresh vegetables, and their popularity accounts in part for this increased vegetable con- sumption. Much of this increase represents french fries and baked potatoes eaten away from home; french fries and baked potatoes with fatty sauces are high-fat foods, in comparison with baked pota- toes without toppings. Lettuce, broccoli, tomatoes, carrots, and cauliflower show increased popularity, probably a reflection of the increased availability of salad bars in fast-food restaurants. There is a growing awareness that vegetables provide materials besides vitamins and minerals that are important for long-term health. Some plant substances ( PHYTOCHEMICALS) are not consid- ered essential nutrients, yet their consumption can have long-term effects on reducing the risk of CAR- DIOVASCULAR DISEASES, CANCER, CATARACTS, AUTOIM- MUNE DISEASES like rheumatoid arthritis, premature senility, and other chronic problems associated with AGING. Plants of the cabbage family, including broccoli, cabbage, and brussels sprouts, produce materials called ISOTHIOCYNATES and indoles, which seem to lower the risk of cancer. Sulfur compounds of onions, garlic, leeks, and chives seem to boost the immune system and inhibit tumors. Many plants including vegetables produce FLAVONOIDS,a broad family of substances that can function as antioxidants to block the oxidative damage to cells due to free radicals. Free radical-induced damage is now believed to be a factor in some degenerative diseases, like heart disease, associated with aging. For example, dark green leafy and orange vege- tables and some fruits are a rich source of CAROTENOIDS , including beta-carotene. These phy- tochemicals function as antioxidants and they enhance the immune system. As a group they reduce the risk of some forms of cancer. Rather than a simple ingredient, vegetables pro- vide a wide array of known phytochemicals; undoubtedly, many more remain to be discovered. Phytochemicals appear to be most effective when supplied in combination with a range of substances as found in minimally processed foods, including vegetables. Their effects are often synergistic, that is, the overall effect of a combination is more ben- eficial than any one isolated ingredient. Vegetable Processing Although fresh vegetables are available year round due to large refrigerated warehouses and fast trans- portation systems, processed vegetables remain an important part of the American diet. A variety of methods are used to prepare or to preserve vegeta- bles. Several of the more common methods include: Canning Developed in the 19th century in France, canning remains a major food preservation strategy. This process involves heating vegetables in metal or glass containers to a sufficiently high tem- perature to destroy microorganisms that cause spoilage or disease. Heat-treated contents are sealed against air to prevent oxidation. Drying Drying food in the sun for preservation has been carried out for thousands of years. Drying must be carried out rapidly to avoid changes in nutrients, flavor, or texture. The action of plant enzymes that darken produce, destroy nutrients and alter flavor can be limited by blanching (a brief heat treatment) or by treatment with preservatives like sulfites or antioxidants such as VITAMIN C. Freezing Commercial techniques for rapid cooling and freezing allow many vegetables to retain most qualities of fresh vegetables for periods vegetables 643 lasting up to eight to 12 months. Blanching slows alterations in flavor, color, and texture of frozen vegetables. Pickling Vegetables can be preserved in a salt solution (brine) or in VINEGAR, or a combination of the two. Pickled cucumber and relishes are common food items. Commercially pickled products require heating to destroy microorganisms and to inactivate plant enzymes that alter vegetables properties. Raw or Cooked Vegetables? There are certain advantages to eating cooked veg- etables. Cooking a vegetable can increase the avail- ability of beta-carotene because it is released from storage sites in plant cells. Cooking starchy vegeta- bles breaks down starch granules so they can be digested. On the other hand there are advantages to eating vegetables raw. Raw vegetables may con- tain higher levels of heat-sensitive nutrients because cooking decreases the content of water- soluble vitamins. For example, baked potatoes and sweet potatoes lose about 20 percent of the B vita- mins and vitamin C. Boiling causes lower losses. Boiling leaches B vitamins and minerals out of veg- etables. Losses may be as high as 80 percent. Steaming and microwave cooking of vegetables greatly reduces this loss. Boiling also removes vita- mins and minerals. Note that keeping foods warm on a steam table increases the loss of vitamins such as vitamin C, thiamin, and riboflavin. On the other hand, vegetables that have not been stored properly, or have been handled care- lessly, can suffer similar nutrient losses. Slicing, mashing, dicing, mincing, and grating break veg- etable cells and expose vitamins to oxygen and degradative enzymes. Vitamin C is especially sensi- tive to oxygen exposure. The longer the storage period for sliced vegetables, the greater the loss of vitamin C. (See also BALANCED DIET; DIETARY GUIDE- LINES FOR AMERICANS; FOOD PRESERVATION; FOOD PROCESSING ; FOOD GUIDE PYRAMID; ORGANIC FOODS.) Graziano, J. M. et al. “A Prospective Study of Consump- tion of Carotenoids in Fruits and Vegetables and Decreased Cardiovascular Mortality in the Elderly,” Annals of Epidemiology 5 (1995): 225–260. vegetable shortening A form of saturated fat, prepared from vegetable oil, that resembles animal fat. A major advantage of vegetable shortening is that, unlike lard, butter, or beef fat, it does not con- tain CHOLESTEROL. Vegetable shortening does con- tain the same high calories as butter or lard, however. Vegetable shortening is a product of the chemical processing called hydrogenation. This process adds hydrogen atoms to unsaturated FATTY ACIDS , thereby converting naturally liquid fat (oils) to materials with varying degrees of stiffness. Usu- ally several different fats are blended to achieve the desired consistency of a shortening. CORN OIL, COT- TONSEED OIL , SOYBEAN oil, OLIVE OIL , PALM OIL, PEANUT oil, SAFFLOWER oil, and SESAME oil may be combined. Shortening, like other hydrogenated vegetable oils, contains TRANS-FATTY ACIDS as a by- product of manufacture. The long-term safety of trans-fatty acids has been questioned. A diet high in saturated fat is linked to an increased risk of HEART DISEASE and CANCER. (See also HYDROGENATED VEGETABLE OIL ; VEGETABLE OIL.) vegetarian One who eats predominantly VEGETA- BLES, FRUITS, GRAINS, and NUTS and either limits or excludes animal products, including MEAT, FISH, SEAFOOD, and dairy products from the diet. With a thoughtful selection of a variety of foods, vegetari- ans can easily meet all their nutrient needs. People choose vegetarianism for a variety of reasons. Vegetarianism may be related to religious or philo- sophical beliefs. Ecologically, vegetarianism repre- sents a more efficient use of energy than relying on meat and meat products. From a health perspec- tive, plant products do not contain the growth pro- moters and antibiotics used in poultry and meat production nor do they contain cholesterol. Plants are excellent sources of FIBER and ESSENTIAL FATTY ACIDS . There are varying degrees of vegetarianism: • Vegans rely on foods of plant origin and omit all meat, poultry, fish, and eggs, as well as milk and meat products. • Fruitarians rely on dry or raw fruits, together with nuts, honey, grains, LEGUMES, and OLIVE OIL while excluding animal products. • Semivegetarians occasionally eat some meat, fish, or poultry, eggs and milk or cheese while relying on cereals, grains, fruit, and vegetables. 644 vegetable shortening Most “heart healthy” diets are semivegetarian diets. There are a variety of such diets. • Ovo-vegetarians include eggs with foods of plant origin in the diet. • Lactovegetarians include milk and milk prod- ucts, together with foods of plant origin. • Lacto-ovo-vegetarians include both milk prod- ucts and eggs with grains, fruits, and vegetables. Vegetarians who eat dairy products tend to have higher blood cholesterol levels than those who do not. • Pescovegetarians include fish and seafood, together with foods derived from plants. Vegetarians may have a reduced risk of obesity, type II (adult onset) diabetes, GALLSTONES, and CORONARY ARTERY DISEASE. There is evidence that vegetarian diets reduce the risk of breast CANCER, DIVERTICULOSIS, colonic cancer, hemorrhoids, OSTEOPOROSIS, and dental caries. Nutrient Needs Vegans who are pregnant or lactating, children of vegans, and people who are ill run the greatest risk for certain nutrient deficiencies because these indi- viduals have high nutrient needs that may not be readily met by eating a limited variety of plant foods. Minerals The amounts of many TRACE MINER- ALS are low in plant products, and the body’s abil- ity to absorb them from plant sources is often low. Milk and milk products provides the most of the calcium and meat provides the most iron and zinc in the usual diet. Vegans may have difficulties in obtaining minerals such as: • CALCIUM. Major plant sources are: BROCCOLI, KALE, COLLARD greens, kelp, PARSLEY, prunes, SE- SAME seeds, fortified TOFU, and fortified soymilk. • ZINC. Sources are: whole grains, BREWER’S YEAST, LIMA BEANS, SOYBEANS, sunflower seeds, PEAS, LENTILS, and wheat germ. • IRON. This nutrient occurs in dried beans and peas, dried fruit, fortified cereals, and bread. Iron uptake can be significantly increased by eating iron-rich vegetable foods with vitamin C- rich foods (citrus fruit, berries, dark green leafy vegetables). • COPPER. Copper occurs in AVOCADOS, BARLEY, BEANS, broccoli, BEETS, PECANS, RAISINS, and soy- beans. • MANGANESE. This nutrient occurs in avocados, NUTS, seeds, whole grains, legumes, dried peas, and dark green leafy vegetables. Energy The energy demands of infants and growing children are quite relative to their body size. Fat is a calorie-dense food that is an important part of a child’s diet. Often vegetarian foods offer high fiber but low energy (fat) content. When the diet provides inadequate calories, a muscle protein is degraded for energy, not a desirable situation in a young, growing body. Protein Dietary protein must supply adequate essential AMINO ACIDS (the amino acids that cannot be fabricated in amounts to meet the body’s requirements). Plant proteins may be less easily digested depending on the meal preparation. Their amino acid compositions are usually not as well balanced as animal protein. Consequently, vegetar- ian diets based on a single grain like corn can con- tribute to MALNUTRITION. Plant proteins from different sources can complement each other, so that the net amino acid intake of a mixture of plant protein can adequately meet the daily requirement for essential amino acids. For example, combining whole grain foods with legumes is a traditional practice (rice and beans, corn and beans, wheat and lentils, for example). Vitamin D The best sources of this vitamin are fatty fish, egg yolk, liver, and milk and milk prod- ucts—all of which are eliminated from a strictly vegetarian diet. Exposure to sunlight may meet individual needs; however, supplementation may be necessary for people living in northern regions of the United States during the winter months, as well as for institutionalized people. B Vitamins A number of cereal grain products are enriched with RIBOFLAVIN, THIAMIN, and NIACIN. Legumes and whole grains can provide significant riboflavin. VITAMIN B 12 deficiency is a major con- cern for strict vegetarians. There is probably no very good plant source, other than nutritional YEAST. The amounts provided in sea vegetables, fer- mented soy, and algae may be inadequate. The best sources are animal products such as meat; thus a vegetarian 645 strict vegetarian may need a supplement, fortified soy milk, or fortified meat analog. Once vitamin B 12 deficiency has occurred, the resulting nerve degeneration may not be reversible. Strict vegetarian diets are not recommended for infants or children. Pregnant women should plan their diet very carefully to maximize nutrient- dense foods and: 1. emphasize unrefined, whole foods; 2. use protein-rich sources like legumes, seeds, and nuts; 3. eat a variety of fruits, vegetables, legumes, and whole grains to assure adequate protein com- plementation; 4. eat fruit and vitamin C-rich foods with each meal to enhance iron uptake; 5. consider supplemental sources of vitamin B 12 , vitamin D, calcium, and trace minerals or prop- erly fortified sources; 6. eat enough food to provide adequate protein and energy. (See also CHOLESTEROL-LOWERING DRUGS; COM- PLETE PROTEIN.) Appleby, P. N. et al. “The Oxford Vegetarian Study: An Overview,” American Journal of Clinical Nutrition 70, suppl. (1999): 525S–531S. Key, T. J. et al. “Health Benefits of a Vegetarian Diet,” Pro- ceedings of the Nutrition Society 58 (1999): 271–275. very low-density lipoprotein (VLDL) A lipid- protein particle that transports FAT from the LIVER to other tissues via the bloodstream. After a carbo- hydrate meal, the liver absorbs glucose from the blood and converts it to fat ( TRIGLYCERIDES). The liver packages fat to export it to other parts of the body via the bloodstream in the form of VLDL. In composition, VLDL resembles chylomicrons, the fat transport vesicles from the intestine. VLDL contains triglycerides, a low amount of CHOLES- TEROL, and two types of protein designated B-100 and C-II. When VLDL reaches the capillaries, its triglyc- erides are broken down by an enzyme in the walls of the capillaries called lipoprotein lipase. Tissues then absorb the released fatty acids. After releasing their fat, VLDL remnants follow an unusual path- way: They become enriched in cholesterol as they are transformed in the blood to LOW-DENSITY LIPOPROTEIN (LDL)—the particle that carries choles- terol to tissues. The blood levels of both chylomicrons and VLDL increase for several hours after eating. Therefore, lab tests that measure triglycerides in serum, the clear cell-free fluid remaining after blood clots, are usually performed after an overnight fast when levels have stabilized. Middle-aged white males with high levels of serum triglycerides (essentially VLDL) and high LDL appear to be more likely to have heart attacks than men with normal levels, even in the people with somewhat elevated serum cholesterol levels. The risk of heart attack may decrease by lowering serum triglycerides and rais- ing HIGH-DENSITY LIPOPROTEIN (HDL), the “desirable cholesterol.” (See also CARDIOVASCULAR DISEASE; FAT METABOLISM .) villi Microscopic, fuzzy layer coating the inner side of the wall of the SMALL INTESTINE like a shag carpet. Cells that line the surface of villi possess numerous, tiny projections called MICROVILLI.If all of the intestinal folds, villi, and microvilli were flat- tened out, the total surface area would be about the size of a tennis court. Thus villi dramatically increase the absorptive area of the intestinal sur- face and facilitate efficient nutrient uptake. CELIAC DISEASE , CROHN’S DISEASE, and intestinal parasitic diseases (like GIARDIASIS) can lead to a loss of the villi and subsequent MALABSORPTION and maldiges- tion syndromes. With appropriate treatment and dietary modification, the villi can grow back and digestion can improve. (See also DIGESTION; DIGES- TIVE TRACK.) villikinin A hormone produced by the SMALL INTESTINE that stimulates the movement of VILLI, microscopic hair-like projections that coat the inner surface of the small intestine. This action serves to mix chewed food and digestive juice ( CHYME) and to increase nutrient absorption by the intestine. (See also DIGESTION; ENDOCRINE SYSTEM.) vinegar A dilute solution of ACETIC ACID. The term is derived from the French vinaigre, which 646 very low-density lipoprotein means sour wine. Vinegar has been used in food preservation and medicine for thousands of years. Typically vinegar contains 4 percent to 12 percent acetic ACID, which is produced by the bacterial oxidation of alcohol formed by the fermentation of sugars and fruits. Apples yield cider vinegar; grapes, wine vinegar; and sugar and hydrolyzed starches from corn and wheat, white vinegar. Depending upon the nature of the fruit fermented, the resulting vinegar will have a unique flavor without adding significant calories. Vinegar pro- vides only two calories per teaspoon. Because it is so acidic, vinegar is used to preserve foods in pickling. In salad dressing, MAYONNAISE, MUSTARD , and tomato sauce, vinegar helps retard spoil- age. Vinegar contains traces of minerals but it is not a significant food source. (See also FOOD PRO- CESSING.) vitamin An essential organic nutrient. Minute amounts of vitamins participate in three general functions of the body: growth, protection, and energy regulation. There are a total of 13 vitamins. Four are fat-soluble vitamins A, D, E, and K. The rest are water-soluble. Eight vitamins are in the B complex: RIBOFLAVIN (B 1 ), THIAMIN (B 2 ), NIACIN (B 3 ), VITAMIN B 6 , vitamin B 12 , FOLIC ACID , PAN- TOTHENIC ACID, and biotin. VITAMIN C is also water- soluble but is not considered a B vitamin, which function as enzyme helpers (coenzymes). Vitamins either cannot be synthesized by the body or they cannot be made in adequate amounts, so they must be supplied by the diet. As examples of the latter, vitamin D can be made in the skin when exposed to sunlight, while some niacin can be made from the amino acid tryptophan. The intestine is a source of BIOTIN, pantothenic acid, and VITAMIN K; these are supplied by “friendly” intesti- nal bacteria, though the exact amounts supplied are difficult to assess. The term vitamin dates from 1912, and the first vitamin to be isolated was vitamin A in 1913. Thi- amin was discovered in 1926, vitamin K in 1929, and vitamin C in 1932. Vitamin B 12 was the most recent vitamin to be discovered (1948). Before a compound can be classified as a vitamin, it must be proven that animals must obtain the compound from their diet. Typically, scientists test lab animals such as mice with a diet free of the test substance, together with a dose of antibiotics to eliminate intestinal bacteria. Vitamins originate chiefly from plant sources. Except for vitamin D and vitamin C, vitamins are present in animal tissue only if the animal con- sumes foods containing them or harbors microor- ganisms capable of synthesizing them. B vitamins are universally distributed; fat-soluble vitamins may be absent from some types of organisms. Each of the vitamins plays a specific role in the body; a deficiency of one vitamin cannot be eliminated by consuming an excess of another. Fat-Soluble Vitamins VITAMIN A, VITAMIN D, VITAMIN E, and vitamin K are oily materials and dissolve in fats and oils, not in water. Unlike the B complex, these vitamins gener- ally do not serve as enzyme helpers, nor are they involved in energy production; each has an entirely different function, ranging from acting as an ANTIOXIDANT (E), to producing a visual pigment for night vision (A), to blood clothing (K), and to bone formation (D). Fat-soluble vitamins are absorbed best when they are eaten with fats and oils. These vitamins are stored in the body, so they do not need to be consumed daily. Because they are stored, excessive consumption can lead to high tissue levels resulting in toxic side effects, especially for vitamins A and D. For example, 50,000 international units of vita- min A over several months can cause toxic symp- toms in adults. Symptoms of toxicity, such as achy joints, fatigue, headaches, and nausea, disappear when the high intake stops. What represents an excessive intake depends on many factors, includ- ing the type of vitamin, individual tolerance, which varies with age, and the length of time for which the supplement is taken. Water-Soluble Vitamins B complex vitamins help convert food into energy; they include THIAMIN (B 1 ), RIBOFLAVIN (B 2 ), NIACIN (B 3 ), VITAMIN B 6 , pantothenic acid, and biotin. FOLIC ACID and vitamin B 12 are involved in build- ing new cells, while vitamin C serves as an antiox- idant and helps build healthy capillaries, gums, and joints. Except for vitamin B 12 , water-soluble vita- mins are not stored well in the body and must be vitamin 647 replenished daily. Excesses are generally excreted in the urine. Vitamin Deficiencies Long-term vitamin deficiencies often lead to seri- ous illness. Deficiencies can be due to an inade- quate diet ( MALNUTRITION); inability to digest food (maldigestion); inability to absorb vitamins due to damage to the intestine or to competition with another material such as a drug ( MALABSORPTION); increased physiological need as during pregnancy; growth, injury, choice of lifestyle, or other envi- ronmental factors. Physicians may use lab tests to diagnose vitamin deficiencies. Most tests involve blood analyses, even though these are not always reliable. For example, a common antibody test for serum vita- min B 12 detects both vitamin B 12 together with inactive derivatives. Measurement of enzyme lev- els or levels of metabolic products can provide use- ful information. Dietary analysis can reveal levels of nutrients in the diet and guide a nutritional eval- uation and assessment of individual needs comple- menting the physical examination and health history. Natural vs. Synthetic Vitamins Natural vitamins are those occurring in food. All substances classified as vitamins have been isolated from animal or plant sources, and most have been chemically synthesized in the lab to establish their structures. In other words, synthetic vitamins are usually identical to the product in cells. As an exam- ple, vitamin C in cells is defined chemically as L- ascorbic acid, identical to synthetic L-ascorbic acid. Most vitamins found in supplements are chemically synthesized, because there simply is not enough of most vitamins extracted from plant materials to meet world demand. Most vitamin C comes from a few major commercial sources worldwide. A few synthetic vitamins differ from the natural forms. Synthetic vitamin E, called d, 1-alpha- tocopherol, is a mixture of both left- and right- handed molecules, while the natural alpha toco- pherol is a single form called d-tocopherol. The synthetic product is adjusted to provide the same biological activity as the natural form. Certain vita- mins like vitamin B 12 possess structures that are too complex for a convenient lab synthesis. Micro- bial sources have been selected to produce large amounts. Vitamin Supplements Nutritionists often recommend obtaining vitamins from foods for several reasons. Foods supply mixtures of vitamins, minerals, and other materials that may have beneficial effects. Mixtures are what the body uses. Foods supply materials that are not vitamins, yet are important. In this class are FLAVONOIDS, which work together with vitamin C to build strong capillaries and serve as antioxidants and as anti-inflammatory agents. Substances with anticancer properties have recently been isolated from vegetables of the cab- bage family; they include isothiocyanates and indoles, in addition to the flavonoids. Recent surveys show that about 158 million consumers take supplements and spend about $8.5 billion yearly on vitamins, minerals, and other sup- plements. One explanation for this widespread practice is that many people have subclinical defi- ciencies. They are not sick, but they are not well, either. They may want to feel more energetic and to have more stable moods. Others want to take supplements as insurance in preventing certain dis- eases if they live in a polluted environment or if their genetic makeup, medical history, and lifestyle choices warrant it. A growing number of con- sumers want to promote optimal health. Although there is a natural tendency to search for an easy solution to health problems, there are limits regarding what vitamins can do for health. No sin- gle supplement can compensate for overindul- gence, physical inactivity, or genetic predisposition. Deciding who needs vitamin supplements and how much should be taken is a controversial area. Conventional wisdom says that by following DIETARY GUIDELINES FOR AMERICANS and using a rec- ommended plan such as the FOOD PYRAMID, an indi- vidual should be assured of an adequate supply of nutrients. Thus, if an individual is healthy and is eating a BALANCED DIET, vitamin supplements would not be needed. There is general agreement that individuals with well recognized needs may require supplements. These people include: • women with heavy menstrual bleeding (extra IRON) 648 vitamin [...]... consumption of vitamin C contributes to higher plasma levels of other antioxidants, including vitamin E Possible Role of Vitamin C in Disease The functions of vitamin C in the body and the amounts required for optimal health remain one of the most controversial areas in nutrition The following topics have been the focus of recent research Scurvy This full-blown vitamin C deficiency disease is characterized by... should have a better idea whether vitamin E is helpful in preventing cardiovascular disease Gamma-tocopherol Alpha tocopherol is the form of vitamin found in highest concentration in blood and tissues due to selection by the intestines and liver However, gamma-tocopherol is the most common form of vitamin E in the diet of typical Americans Some studies suggest that alphatocopherol, the form of vitamin... known Safety There is general agreement that amounts up to 50 mg per day are relatively safe Higher levels should be taken only with professional advice Excessive consumption of vitamin B6 can damage the nervous system and lead to numbness of hands and feet (peripheral neuropathy) Insomnia and anxiety are possible symptoms of excessive intake Vitamin B6 reduces the effectiveness of levodopa, a drug... fat-soluble vitamin and one of the first vitamins to be discovered Vitamin A is required for a healthy immune system, vision, 650 vitamin A growth, and reproduction Vitamin A supports normal tissue development, which accounts for its influence on taste and hearing The liver stores 90 percent or more of this vitamin Many plants produce a parent compound of vitamin A called BETACAROTENE, also called “provitamin... and aging This vitamin plays important roles in the immune system, the nervous system and the endocrine (hormonal) system Possible Roles in Maintaining Health Cancer Studies to determine whether vitamin E is effective in the treatment or prevention of cancer have been inconclusive Some studies have shown that patients who take supplements of vitamin E decrease their risk of colon cancer while in others... A.” This orange-yellow pigment is stored in fat tissue and other tissues, but comparatively little is stored in the liver, unlike vitamin A Beta-carotene is cleaved to form retinol and an inactive molecule called retinoic acid, which lacks vitamin A activity Vitamin A and Vision Perhaps the best known role for vitamin A is its effect on vision Vitamin A forms a pigment in the eye called visual purple,... beta-carotene, vitamin E can decrease the progression of moderate to severe age-related macular degeneration Immune System Moderate amounts of vitamin E seem to increase the ability of macrophages to destroy bacteria and to boost activity of T lymphocytes, the foot-soldiers and generals of the IMMUNE SYSTEM Vitamin E may alter production of certain PROSTAGLANDINS, hormone-like substances derived from essential... rate of mortality due to HIV Because retinoic acid may increase HIV replication, beta-carotene could be the preferred form for supplementation Sources Vitamin A is either supplied as such in food, or it is formed from beta-carotene in the body Fish liver oil and liver are rich in vitamin A Milk is fortified with vitamin A Vitamin A palmitate is often the form of the vitamin found in supplements Its advantage... and contaminate the food supply Derivatives of hydrazines appear in cigarette smoke and food additives, thus, the environmental burden could deplete this nutrient Possible Roles in Maintaining Health Red Blood Cells Vitamin B6 is essential for the production of RED BLOOD CELLS Vitamin B6 plays a role in protein synthesis as well as in the synthesis of DNA and RNA, and it is required to make HEME, the. .. prevent recurring tumors of the head and neck Another derivative of vitamin A, tretinoin (retin A), may be able to combat precancerous cervical conditions Skin Conditions Vitamin A can clear up ACNE but extremely large doses are required to do so, increasing the risk of toxicity Derivatives are more effective; for example, tretinoin clears up the most common form of acne, acne vulgaris, and another . pressure in the legs and may lead to the development of varicose veins. Standing places heavy pressure against leg veins, and the extra weight of the blood stretches the walls of the vessels, which. can reveal levels of nutrients in the diet and guide a nutritional eval- uation and assessment of individual needs comple- menting the physical examination and health history. Natural vs. Synthetic. starchy vegeta- bles breaks down starch granules so they can be digested. On the other hand there are advantages to eating vegetables raw. Raw vegetables may con- tain higher levels of heat-sensitive