Vitamins, Carotenoids, and Phytochemicals

September 2001

WHAT ARE VITAMINS, CAROTENOIDS, AND PHYTOCHEMICALS?

Vitamins

Vitamins do not share a common chemistry, but they do share certain characteristics. They are all organic nutrients that are necessary in small amounts for normal metabolism and good health. Most vitamins must be provided by the diet or by supplements; only three vitamins (D, K, and the B vitamin biotin) can be manufactured in the body from nondietary sources. Vitamins are not sources of energy as are carbohydrates, fats, and proteins. Instead, vitamins serve as chemical partners for the enzymes involved in the body's metabolism, cell production, tissue repair, and other vital processes. Vitamins are either fat soluble or water soluble. The fat-soluble vitamins, which include A, D, E, and K, are absorbed by the body using processes that closely parallel the absorption of fat. They are stored in the liver and used up by the body very slowly. The water-soluble vitamins include C and the B complex vitamins. The body uses these vitamins very quickly; excess amounts are eliminated in urine.

Phytochemicals

Phytochemicals is simply a word that means plant chemicals. Hundreds of phytochemicals are currently being studied. Many are believed to have a major positive impact on human health. Some contribute to the bright and vivid colors found in fruits and vegetables. The results of studies on specific phytochemicals are not necessarily applicable to the vegetables or fruits that harbor small concentrations of these chemicals. Nevertheless, it is obvious that vegetables and fruits are healthful, which is probably due to some balance of phytochemicals, carotenoids, vitamins, fibers, and minerals rather than any single substance. It should be stressed that very little has been proven concerning the benefits of phytochemical supplements sold in health food stores. Furthermore, high concentrations of some of these chemicals may behave like drugs and can be toxic and possibly even contribute to cancer cell growth.

Carotenoids

Carotenoids are a group of more than 700 compounds that produce the red, yellow, and orange colors found in many fruits and vegetables. Beta carotene (also called provitamin A) is the most widely studied carotenoid, but others are proving to be of great interest. Carotenoids are neither vitamins nor phytochemicals, but are proving to be very important for health. Currently there is no recommended daily allowance for carotenoids, including beta carotene.

HOW ARE VITAMINS AND OTHER NUTRIENTS RATED AND REGULATED?

Guidelines for Adequate Intake

The Recommended Daily Allowance (RDA) for vitamins, set by the Food and Nutrition Board of the National Academy of Sciences-National Research Council, has been used for years as a guide for determining the amount of vitamins needed for a healthy diet.

The RDA is gradually being enhanced using a new standard called the Dietary Reference Intake (DRI). The DRI is a standard based on four different rating sets, including the tolerable upper intake level (UL), which is the maximum dose likely to be safe in nearly all individuals.

Food and supplements labels now typically list the Daily Value (DV). This is the percentage of the amount of a nutrient that experts believe a person needs in their daily diet. On food labels it is usually based on one serving size for a person who takes in 2000 calories a day.

Regulating Quality

The essential problem is that there is no control over what goes into a dietary supplement and not enough known about long term benefits and risks from taking supplements. Brands also differ in quality and in the ability of vitamins to be absorbed by the body; it is nearly impossible for the average consumer to compare them wisely. In selecting vitamins, one might keep in mind the following factors:

Government recommendations only suggest the basic known requirements for vitamins. They do not indicate anything about their specific effects on health, which are largely unknown.
The US Pharmacopoeia, an independent organization that sets standards for drugs, has also implemented standards for vitamins. Consumers should look for the USP label on products of companies that adhere to these standards.
Shopping for the lowest-priced vitamins is the wisest move. There appears to be no significant differences in quality between the vitamins in the lowest and those in the highest price ranges.
The FDA is now requiring that vitamins and other dietary supplements include labels similar to those found on all commercial foods. The label will include nutrient information and list all ingredients, including identifying parts of plants from which ingredients may be taken, but the quality of the supplement will not be evaluated.
Most importantly, studies continue to report that the most important health benefits are derived from foods containing important nutrients, not individual supplements.

WHAT ARE THE SPECIFIC VITAMINS AND THEIR DEFICIENCIES AND TOXICITIES?

Vitamins	Vitamin A
Benefits	Essential for growth, bone development, night vision, reproduction, and healthy skin.
Recommended daily allowance (RDA) or dietary reference intake (DRI) (mcg = micrograms, mg = milligrams, IU = international units)	Vitamin A is also now being measured with a new unit called the Retinol Activity Equivalent (RAE or RE). One RE is equal to 1 mcg. Retinol is the most active form of vitamin A and it is also converted in the liver from carotenoids. Vitamin A RDA for children is 400 RE (2000 IU) ages one to three, 500 RE (2500 (IU) four to six, and 700 RE (3,500 (IU) for seven to 10. RDA for ages 11 through adulthood is 1000 RE (5000 IU) for men, 800 RE (4000 IU) for women (including during pregnancy and nursing). The upper limit because of toxicity is 1600 to 2000 RE (8000 to 10000 IU) in most adults, with the upper limit being 1600 RE (8000 IU) in pregnant women. (One RE is equal to 12 mcg of beta-carotene or 24 mcg of alpha-carotene or beta-cryptoxanthin).
Foods containing the vitamin	Animal products, such as liver, dairy products, eggs, and fish liver oil. Retinol from vitamin A and carotenoids is also found in dark red, green, and yellow vegetables. Requires some dietary fat to be absorbed.
Effects of deficiencies	Skin disorders and eye damage. In less developed countries severe deficiencies cause blindness in 250,000 children each year. Diets low in vitamin A may also increase the risk of developing cancer.
People at risk for deficiencies	Preschool children or pregnant or nursing women with inadequate diets. People with high-risk medical problems: intestinal disorders (such as cystic fibrosis, steatorrhea, and biliary obstruction), hyperthyroidism, liver diseases (such as cirrhosis).
Toxicities	Very toxic when taken in high-dose supplements for long periods of time. Symptoms of overdose include dizziness, nausea, vomiting, headache, skin damage, mental disturbances, and, in women, infrequent periods. Can affect almost every part of the body, including eyes, bones, blood, skin, central nervous system, liver, and genital and urinary tracts. Severe toxicity can cause blindness and may even be life threatening. Liver damage can occur in children who take RDA-approved adult levels over prolonged periods of time or in adults who take as little as five times the RDA-approved amount for seven to ten years. In children, chronic overdose can cause fluid on the brain and other symptoms similar to those in adults. Pregnant women who take amounts not much higher than RDA levels increase the risk for birth defects in their children. High consumption of vitamin A may also increase the risk of gastric cancer and the risk of osteoporosis and fractures in women.

B Vitamins	General information	Vitamin B1 (thiamin)
Benefits	The B vitamins have a wide and varied range of functions in the human body. Most B vitamins are involved in the process of converting blood sugar into energy.	Essential for converting blood sugar into energy and is involved in metabolic activities in nerves, heart, and muscles and in the production of red blood cells.
Recommended daily allowance (RDA) or dietary reference intake (DRI) (mcg = micrograms, mg = milligrams, IU = international units)		RDA is 1.2 mg per day for men and 1.1 mg for women.
Foods containing the vitamin		Best source is pork and good sources are dried fortified cereals, oatmeal, corn, nuts, cauliflower, and sunflower seeds. Supplements for people with normal diets and health are unnecessary.
Effects of deficiencies	Deficiencies are uncommon in the US, but when they occur, they usually involve several B vitamins, since many of them come from the same food groups.	Severe vitamin B1 deficiency is known as beriberi. Can cause visual disturbances, paralysis, staggering, loss of sensation in the legs and feet, psychosis, and congestive heart failure.
People at risk for deficiencies	Alcohol interferes with these vitamins, and some of the physical and mental problems that alcoholics experience may be attributed to a deficiency of B vitamins. Elderly people are also at risk for deficiencies because of inadequate diets and potential interference with B-vitamin absorption by medications. Deficiencies can occur in severely malnourished people or in those receiving long-term dialysis or intravenous feeding.	See general vitamin B description.
Toxicities	Because the B vitamins are water-soluble and eliminated in the urine, toxic reactions from oral administration of most of them are extremely rare. (Exceptions are niacin and B6.) It should be noted that substances known as B15 (pangamic acid) and B17 (laetrile) are neither vitamins nor nutrients; both chemicals are highly dangerous and have no proven nutritional or health value.	No toxic effects have been reported from thiamin.

B Vitamins	Vitamin B2 (riboflavin)	Vitamin B3 (niacin) also known as nicotinic acid	Vitamin B5 (Pantothenic Acid)
Benefits	Important in the production of energy.	Helps break down blood sugar for energy. Acts as a *vasodilator*, widening blood vessels and increasing blood flow. May be prescribed for improving cholesterol levels.	Important for metabolism of fats, carbohydrates, and proteins, as well as production of steroid hormones and other important chemicals.
Recommended daily allowance (RDA) or dietary reference intake (DRI) (mcg = micrograms, mg = milligrams, IU = international units)	DRI is 1.7 mg.	DRI is 20 mg.	Adequate intake (AI) is 4 to 7 mg.
Foods containing the vitamin	Liver, dried fortified cereals, and low fat yogurt. Supplements for people with normal diets and health are unnecessary.	Mackerel, swordfish, chicken, veal, dried fortified cereals, pork, salmon, and beef liver. Supplements are unnecessary in people with normal health and diets.	Whole grains, beans, milk, eggs, and liver. Supplements are unnecessary in people with normal health and diets.
Effects of deficiencies	Deficiencies affect the skin and mucous membranes and can cause cracks on the lips or corners of the mouth, eczema of the face and genitals, a burning sensation on the tongue, or eye irritation.	Deficiency causes pellagra; symptoms can include eczema, intestinal and stomach distress, depression, headache, thinning of the hair, and excess saliva production.	Deficiency is unlikely except in company with other B vitamin deficiencies. Symptoms include abdominal distress, burning sensation in the heels, and sleep problems.
People at risk for deficiencies	See general vitamin B description.	Alcoholics and any malnourished persons.	Alcoholics and any malnourished persons.
Toxicities	Until recently, no toxic effects had been reported even from large doses of riboflavin. However, one study indicated that high consumption of vitamin B2 might increase the risk of stomach cancer. More research is needed. (In the same study, vitamins B1, B3, and B6 were protective.)	Even mildly high doses of niacin can cause hot flushing of the face and shoulders, headache, itchiness, and stomach problems. Some report heart disturbances and temporarily lowered blood pressure. Large doses may produce ulcers, gout, diabetes, and liver damage, which are usually reversed when high doses are discontinued.	Although no toxicity has been reported in humans, high dosages have caused liver damage in rats.

B Vitamins	Vitamin B6 (pyridoxine)	Vitamin B12 (cobalamin)
Benefits	Has an effect on over 60 proteins in the body, importantly, those that play a role in the nervous system, in red and white blood cell production, and in heart disease.	Essential for the production of blood cells, manufacturing genetic material, and for healthy functioning of the nervous system.
Recommended daily allowance (RDA) or dietary reference intake (DRI) (mcg = micrograms, mg = milligrams, IU = international units)	RDA is 2 mg in all adults (possibly 3 to 6 mg for people who need heart protection).	RDA is 2.4 mcg in men and nonpregnant women, 2.6 mcg in pregnant women, and 2.8 mcg in nursing mothers.
Foods containing the vitamin	Meats, oily fish, poultry, whole grains, dried fortified cereals, soybeans, avocados, baked potatoes with skins, watermelon, plantains, bananas, peanuts, and brewer's yeast.	The only natural dietary sources are animal products, including meats, dairy products, eggs, and fish (clams and oily fish are very high in B12). Like other B vitamins, however, B12 is added to commercial dried cereals.
Effects of deficiencies	Importantly, increased levels of homocysteine, associated with heart disease, birth defects, and possibly Alzheimer's disease and dementia. Skin problems and nervous system disorders, including impaired memory and concentration. Increased risk for kidney stones.	Severe depression, memory loss, instability, disorientation, and decreased reflexes, and possibly hearing loss. Deficiencies also elevate homocysteine [see vitamin B6, above]. A genetic defect that causes vitamin B12 deficiencies is responsible for pernicious anemia, a serious disorder, which must be treated with injections of vitamin B12 or else neurologic damage may occur.
People at risk for deficiencies	Alcoholics and any malnourished person. In rare cases, infants are born unable to metabolize pyridoxine; in such cases seizures or convulsions can occur, and vitamin B6 must be administered.	Alcoholics and any malnourished persons. Evidence suggests deficiencies may be caused by *Helicobacter* pylori (H. pylori ) bacteria (a cause of ulcers). The elderly may have trouble absorbing natural vitamin B12 and require supplements. Vegetarians are at higher risk for deficiencies.
Toxicities	Very high doses (2,000 mg per day) can cause nerve damage with symptoms of instability and numbness in the feet and hands, which may be permanent in some cases. Pyridoxine also reduces the effects of L-dopa, the drug used for Parkinson's disease.	There is no evidence of toxicity with this vitamin.

B Vitamins	Biotin (a vitamin B)	Choline (a vitamin B)	Folate, or Folic Acid, its synthetic form (a vitamin B)
Benefits	Involved in the production of amino acid proteins and fatty acids.	Essential for fetal brain development and for learning and memory.	Important for many metabolic processes in the body. It is used in the manufacturing of neurotransmitters (chemical messengers in the brain), in protecting the heart, and for synthesizing genetic materials (DNA) in the cells. It also protects the heart, possibly by improving blood flow and reducing levels of homocysteine, a possible risk factor for heart disease. Populations with diets rich in folate have lower rates of heart disease and stroke.
Recommended daily allowance (RDA) or dietary reference intake (DRI) (mcg = micrograms, mg = milligrams, IU = international units)	There is no DRI for biotin; some experts suggest 30-100 mcg.	RDA 425 mg for nonpregnant women, 450 mg for pregnant women, and 550 mg for nursing women.	Supplements may be folate (natural) or folic acid (synthetic). Folic acid is nearly twice the potency of folate. DRI is 400 mcg (.4 mg) of folate for the general population. Some experts recommend 400 mcg of folic acid for heart protection, although one study suggested 800 mcg (.8 mg) a day is necessary to reduce homocysteine levels. Women who are planning to be pregnant should certainly take 400 mcg of folic acid before conception, during pregnancy, and while nursing.
Foods containing the vitamin	Dietary sources are eggs, milk, liver, mushrooms, bananas, tomatoes, whole grains, nuts, and brewer's yeast. Also produced by bacteria in the intestines.	Peanuts, eggs, cauliflower, and meats, especially liver.	Avocado, bananas, orange juice, cold cereal, asparagus, fruits, green, leafy vegetables, dried beans and peas, and yeast. Folic acid supplements are now added to commercial grain products.
Effects of deficiencies	Deficiencies are almost unheard of.	Low levels during pregnancy increase risk of birth defects in newborns.	Low levels during pregnancy increase risk of birth defects in newborns. Deficiencies can also cause megaloblastic anemia and impair concentration, memory, and hearing. As with vitamins B6 and B12, deficiencies elevate homocysteine, which may increase the risk for heart disease
People at risk for deficiencies			Alcoholics, malnourished persons, people with conditions that disturb the small intestine, people taking certain drugs, particularly methotrexate. Other risk factors for deficiency: high-dose aspirin, smoking, treatment for seizures, taking oral contraceptives.
Toxicities		Excessive doses can cause intestinal problems, and there is also some concern that high doses can be carcinogenic.	A link between high doses and central nervous system disorders, zinc deficiency, and seizures in epileptics. This risk appears to be low, but results indicate that megadoses should be avoided. High amounts in the elderly may mask symptoms of vitamin B12 deficiencies.

Vitamins	Vitamin C (Ascorbic Acid)
Benefits	Acts as an antioxidant (reduces harm from damaging chemical processes in the body). Essential for the production of collagen, the basic protein in bones, cartilage, tendons, and ligaments. May help boost the immune system.
Recommended daily allowance (RDA) or dietary reference intake (DRI) (mcg = micrograms, mg = milligrams, IU = international units)	DRI is 75 mg (women) and 90 mg (men). (Smokers need an additional 35 mg.)
Foods containing the vitamin	Citrus fruits and juices, papayas, hot chili peppers, bell peppers, broccoli, potatoes, kale, red cabbage, cauliflower, cantaloupe, sweet potatoes, and Brussels sprouts. Good sources are tomatoes and potatoes.
Effects of deficiencies	Scurvy is the primary deficiency disease. Affects most body tissues, particularly bones, teeth, and blood vessels. Early symptoms include tiredness, weakness, irritability, weight loss, and vague muscle aches. Later symptoms are bleeding gums, wounds that won't heal, rough skin, and wasting away of the muscles. Even modest deficiencies may contribute to periodontal disease. Low dietary intake of vitamin C may also increase lead levels in the blood.
People at risk for deficiencies	Deficiency has been uncommon in the US, usually occurring in the elderly, alcoholics, cancer patients, and some food faddists. Surprisingly, however, studies now suggest that as many as 16% of middle-aged Americans, with the highest risk in smokers and middle aged men, are deficient in vitamin C. High doses of aspirin taken over a long period of time can interfere with vitamin C.
Toxicities	Tolerable upper limit is 2000 mg/ day. High doses may cause headaches and diarrhea. Long-term high doses may increase risk for kidney stones. Ascorbic acid increases iron absorption so people with blood disorders, such as hemochromatosis, thalassemia, or sideroblastic anemia, should avoid high doses. Large doses may also thin blood and interfere with anticoagulant medications, blood tests used in diabetes, and stool tests. Rebound scurvy can occur after abrupt withdrawal from long-term large doses. This may affect infants or pregnant women who withdraw suddenly from high doses.

Vitamins	Vitamin D
Benefits	Vitamin D is actually a single term for several hormones that are stored mainly in the liver and also in fat and muscle tissue. Essential for maintaining healthy bone structure because of its role in the absorption and metabolism of calcium. It is easily absorbed during digestion and is excreted from the body very slowly.
Recommended daily allowance (RDA) or dietary reference intake (DRI) (mcg = micrograms, mg = milligrams, IU = international units)	RDA is 200 IU (5 mcg) per day for children and most adults, 400 IU (10 mcg) for people between ages 50 and 60, and 600 IU (15 mcg) for those over 70 who do not have sufficient exposure to sunlight. Breast fed infants may need supplements.
Foods containing the vitamin	Manufactured in the body from a chemical reaction to the ultraviolet radiation in sunlight and is found in a few food sources, including vitamin D fortified milk, fatty fish, egg yolk, and liver.
Effects of deficiencies	Softening of the bones caused by low amounts of calcium and phosphorous (called rickets in children and osteomalacia in adults). Also increases the risk for hip fractures in postmenopausal women. Associated with a higher risk for prostate cancer and breast cancer risk. Muscle disease.
People at risk for deficiencies	Older people, particularly if they live in the North, who are underexposed to sunlight. Obesity may also increase risk. One 1998 study suggests that vitamin D deficiency may be a significant problem in general in the US even among younger adults. Increasing incidence of rickets being observed, particularly in African American infants, due to higher rates of breast feeding and less exposure to sunlight. Exposure to sunlight for about 15 to 20 minutes at mid-morning or mid-afternoon three times a week is recommended for most people who live in temperate climates.
Toxicities	Vitamin D is very toxic in high doses. In infants, daily amounts higher than 1000 IU can cause mental and growth retardation, kidney failure, and death. In children and adults, daily amounts over 50,000 IU can cause weakness, anorexia, vomiting, diarrhea, and mental changes. Prolonged use of megadoses can cause calcification of soft tissue and life-threatening kidney failure. Low-calcium diets and withdrawal from the vitamin can usually reverse the side effects except for kidney failure.

Vitamins	Vitamin E (Tocopherol or Tocotrienol)	Vitamin K
Benefits	A fat-soluble antioxidant vitamin that helps prevent cell membrane damage and may inhibit oxidation of LDL cholesterol (a process that increases its harmful effects on arteries).	The most important function of vitamin K is its role in blood clotting and prevention of bleeding. The vitamin also contributes to maintaining healthy bones and healing fractures.
Recommended daily allowance (RDA) or dietary reference intake (DRI) (mcg = micrograms, mg = milligrams, IU = international units)	RDA is 10 mg for men and 9 mg for women. Vitamin E is composed of 8 compounds (four tocopherols and four tocotrienols). Vitamin E is most often available as supplements of dl alpha tocopherol (a synthetic form). Natural vitamin E, called d-alpha- or RRR-alpha-tocopherol succinate (VES) may prove to be more active. Other vitamin E compounds include tocotrienol and beta and gamma tocopherol. Supplements that contain a combination of some of these forms may be most beneficial.	RDA is 60 to 65 micrograms (women) and 70 to 80 micrograms (men).
Foods containing the vitamin	Vegetable oils (particularly wheat germ oil), sweet potatoes, avocados, nuts, sunflower seeds, and soybeans. Tocotrienol (a possibly beneficial form) is found in natural tropical oils. Palm oil sold in the US is refined and does not contain tocotrienol.	Best dietary sources are canola oil, cruciferous vegetables, and soybean oil. Good sources are beef liver, bran, and olive oil. Also produced by bacteria in the intestines.
Effects of deficiencies	Deficiencies have not been established.	Easy bruising, bleeding. May increase the risk of hip fractures in women.
People at risk for deficiencies		Deficiency is very uncommon but may occur in patients who have problems absorbing fats, such as those with cirrhosis, people who are on long-term antibiotic therapy, or who are taking other medications, including cholestyramine, Dilantin, and phenobarbital.
Toxicities	Upper level recommended is 1,100 IU of dl-alpha tocopherol. Large doses may cause bleeding problems, particularly in people taking anti-clotting medications. Some research now indicates that vitamin E, like other antioxidants, may have pro-oxidant and damaging effects.	Allergic-type responses, including rash and itching, to high doses have been reported. Those who are taking Coumadin, an anticoagulant, should not take vitamin K without consulting a physician.

WHAT ARE SPECIFIC CAROTENOIDS?

Carotenoids are fat soluble nutrients and categorized as either xanthophylls or carotenes according to their chemical composition. Carotenoids are found in foods such as carrots, pumpkins, sweet potatoes, tomatoes, and other deep green, yellow, orange, and red fruits and vegetables. Most xanthophylls are found in green leafy vegetables and most carotenes are found in yellow vegetables. They are easily destroyed in cooking, particularly xanthophylls.

Beta Carotene and other Provitamin A Carotenoids. Beta carotene, alpha-carotene, beta-cryptoxanthin are carotenes that are converted into vitamin A or retinol (the active form of vitamin A) in the body. They are found in many yellow fruits and vegetables. Beta carotene is the most widely studied carotenoid.

Lutein and Zeaxanthin. Lutein and zeaxanthin are both stored in the retina of the eye. Neither converts to vitamin A. Both are powerful antioxidants and may be very important for healthy eyes. They are found in many yellow fruits and vegetables. Lutein is also in green vegetables, such as broccoli, cabbage, and kale.

Lycopene. Lycopene is responsible for the red color in fruits and vegetables, including tomatoes, red grapes, watermelon, and pink grapefruit. It is also found in papayas and apricots. It does not convert to vitamin A but may have important cancer fighting properties and other health benefits.

WHAT ARE SPECIFIC PHYTOCHEMICALS?

Flavonoids

Flavonoids (or catechins) are important members of a phytochemical family called polyphenols. Certain ones, such as quercetin and catechin (found in onions, wine, and tea), are more active than others and may have powerful benefits. Laboratory studies have shown that specific flavonoids suppress tumor growth, interfere with sexual hormones, prevent blood clots, and have anti-inflammatory properties. Flavonoids are found in celery, cranberries, onions, kale, broccoli, apples, cherries, berries, tea, red wine or purple grape juice, parsley, soybeans, tomatoes, eggplant, and thyme. Most common berries contain flavonoids and are particularly rich in potent antioxidants.

Isoflavones (Phytoestrogens)

Isoflavones, commonly known as phytoestrogens, have actions that are similar to the female hormone estrogen. Isoflavones include compounds called genistein, daidzein, enterolactone, and equol. They act as antioxidants and tumor suppressors. These compounds may improve cholesterol, prevent bone loss, and suppress enzymes that stimulate certain cancers. Isoflavones are mainly found in soy products (not soy sauce) with smaller amounts found in chick peas, flax and other seeds, barley, and milk products from cows feeding on clover.

Lignan is another phytoestrogen and is found in the fiber layers of whole-grains, berries, some seeds, some vegetables, and a few fruits.

Isothiocyanates

Isothiocyanates and related substances, indoles, are also known as mustard oils and are responsible for the sharp taste in cruciferous (also called brassica) vegetables. Such vegetables include broccoli, cabbage, Brussels sprouts, cauliflower, collards, kale, kohlrabi, mustard greens, rutabaga, turnips, and bok choy. Isothiocyanates also stimulate enzymes that convert estrogen to a more benign form and may block steroid hormones that promote breast and prostate cancers. (Cruciferous vegetables are also high in fiber, vitamin C, and selenium.)

Monoterpenes

Monoterpenes have two important phytochemicals, perillyl alcohol and limonene. They block proteins that stimulate cell growth and reproduction and are being tested for actions against cancer. Limonene is found in the peels of citrus fruits.

Organosulfur Compounds

Organosulfurs are part of the allium family of phytochemicals. Compounds, such as allicin, may have benefits on the immune system, assist the liver in rendering carcinogens harmless, and reduce production of cholesterol in the liver. These compounds are found in garlic, leeks, onions, chives, scallions, and shallots.

Saponins

Saponins are forms of carbohydrates that neutralize enzymes in the intestines that may cause cancer. They also may boost the immune system and promote wound healing. Saponins are found in ginseng, beans (including soy beans) and whole grains.

Capsaicin

Capsaicin seems to reduce levels of substance P, a compound that contributes to inflammation and the delivery of pain impulses from the central nervous system. Research suggests that it may inhibit cancer-generating substances. It is found in hot red peppers.

Sterols

Sterols, which include sitosterol, stigmasterol, campesterol, and squalene, are found in vegetable oils. Sitosterol is the most studied and appears to have cholesterol-lowering effects.

WHAT ARE THE BENEFITS OF VITAMINS, CAROTENOIDS, AND PHYTOCHEMICALS?

The benefits of any dietary factors are very difficult to prove, and, in fact to date there is no hard evidence that any supplement protects against any major disease. Studies on population groups may not consider other lifestyle or genetic factors. They often rely on people self-reporting their own dietary habits and often such surveys only reflect short-term eating habits. Other studies are done in the laboratory on animals or blood samples, which may not reflect the effects of nutrients on humans. Nevertheless, it is never wrong to eat plenty of fresh fruits and vegetables and whole grains, the primary sources of vitamins, carotenoids, and vitamins, as well as of fiber and important minerals.

Antioxidant Properties

Oxidants. Currently, the most important benefit claimed for vitamins A, C, E, and many of the carotenoids and phytochemicals is their role as antioxidants, which are scavengers of particles known as oxygen-free radicals : (also sometimes called oxidants). These chemically active particles are by-products of many of the body's normal chemical processes. Their numbers are increased by environmental assaults, such as smoking, chemicals, toxins, and stress. In higher levels, oxidants can be very harmful:

They can damage cell membranes and interact with genetic material, possibly contributing to the development of a number of disorders including cancer, heart disease, cataracts, and even the aging process itself.
Oxygen-free radicals can also enhance the dangerous properties of low-density lipoprotein (LDL) cholesterol, a major player in the development of atherosclerosis.

Antioxidants. Antioxidant vitamins (A, C, and E), carotenoids, and many phytochemicals can neutralize free radicals and may reduce or even prevent some of their damage. Unfortunately, although it is clear that vitamins are required to prevent deficiency diseases, the possible benefits of higher-dose supplements are still unproven in most cases. To date, there is no strong evidence that antioxidant supplements offer any real protection.

Of special note, there is some increasing evidence that high doses of vitamin C, vitamin E, and beta carotene supplements may have pro-oxidant effects , which can be harmful in certain cases. Everyone should try to obtain these nutrients from dark colored fresh fruits and vegetables, which contain balanced teams of antioxidant vitamins and nutrients. [ See Box Special Warning on Antioxidant Supplements.]

Protection against Heart Disease

Vitamins. Deficiencies in Vitamins A, C, E, and beta carotene have been linked to heart disease. All of these nutrients have antioxidant effects and other properties that may benefit the heart. Many studies have been undertaken to determine if such actions are powerful enough protect the heart in people. The evidence for protection from vitamins or other supplements, however, is quite weak, and in fact each of these supplements may be harmful in high doses.

Vitamin E. Vitamin E may prevent blood clots and the formation of fatty plaques and cell proliferation on the walls of the arteries. Experts have hoped that supplements of this vitamin would prove to be protective. However, many studies have found little or no benefits. One major 2000 study, for example, reported that patients who took natural forms of vitamin E at 400 IU for four to six years were not protected against cardiovascular disease. Still, the evidence is not altogether straight forward. Of interest, however, are studies suggesting that 1200 IU of the natural alpha tocopherol form of vitamin E reduces inflammation and damage in the blood vessels, and one suggested that these effects may be of particular benefit for people with type 2 diabetes. Other vitamin E compounds, including gamma tocopherol or tocotrienol may also have specific benefits. Studies are fairly consistent in indicating that eating foods rich in natural vitamin E may be protective.
Vitamin C. Vitamin C appears to maintain blood vessel flexibility and to improve circulation in the arteries of smokers. Generally, such findings have occurred in the laboratory. In one English 2001 study, people whose diets were rich in foods that elevated levels of vitamin C in their blood were at lower risk for heart disease, overall poor health, and death. There is no evidence, however, that supplements of vitamin C offer any actual protection against heart disease. And there is some evidence that high doses may even speed up existing damaging processes in the arteries.
Folate, B6, and B12 Vitamins. Several important studies have demonstrated a link between deficiencies in the B vitamins folate, B6, and B12 and elevated blood levels of homocysteine, an amino acid believed to be a risk factor for atherosclerosis. Both B12 and folate reduce homocysteine levels, although it is not yet clear if this effect is actually protective against heart disease. (Homocysteine may simply be a marker, not a cause, of heart disease.) Major studies are under way and early results of small studies are promising. A 2001 study, for example, reported lower rates of heart disease in populations that had high levels of folate and B12 regardless of any other risk factors. Dosage of 0.8 mg/ day of folic acid appears to be necessary for reducing homocysteine levels. Folate also improves blood flow through the arteries, which may be of equal or greater importance for the heart than its effect on homocysteine.
Niacin (vitamin B3) is used for lowering unhealthy cholesterol levels. Although vitamin B3 is available over the counter, a physician should prescribe niacin in order to ensure its safety and effectiveness. [For more information, see the Well-Connected Report #23, Cholesterol.]

Carotenoids. Studies have reported that a high intake of fruits and vegetables containing beta carotene, lycopene, and other carotenoids may reduce the risk of heart attack. For example, lycopene-poor diets (particularly lycopene in tomatoes) were associated with a significantly higher risk of heart disease and stroke. In another study involving animals, lutein protected against early hardening of the arteries. It should be stressed, however, that studies are continuing to indicate that high doses of supplements of any of these antioxidants have pro-oxidant effects that can harm the arteries and incur other damage.

Phytochemicals.

Flavonoids, particularly those found in both black and green tea, onions, red wine or red grape juice, and apples, may protect against damage done by cholesterol and help prevent blood clots. Drinking as little as a cup of tea a day appeared to help protect against heart disease. Both black and green tea are beneficial. It is now fairly established that a glass or two of red wine a day may be healthful. For people who cannot drink alcohol, juice from red grapes may be beneficial.
Organosulfurs found in onions and garlic have been under investigation for possible beneficial effects on cholesterol levels. Two well-conducted studies found no heart-benefits from taking capsules equivalent to between one and one and a half garlic cloves a day. The preparation of these products, however, may be responsible for the lack of effect. On a more positive note, a 2000 study reported an association between taking garlic capsules and significantly lower cholesterol-build up in the arteries of older women but not in older men. In the study, daily garlic supplements dramatically reduced the build-up of newly formed plaque in the arteries, while having much less effect on older, harder plaque deposits. Garlic supplements for cardiovascular disease may be most beneficial, then, when used during earlier years among men and later years among women.
Soy protein, which is high in isoflavones (known as phytoestrogens, or plant estrogens), has been associated in some studies with heart protection. A number of studies have indicated that subjects who consume about 40 grams of soy protein each day reduce LDL and triglycerides and increase HDL. Powdered soy protein that contains at least 60 mg of isoflavones may provide similar benefits. (Tablets of individual isoflavones found in soy, however, do not appear to offer any advantages.) Of possible concern, a high intake of soy during pregnancy may have some adverse effect on the fetus, although only animal studies have suggested this. More research is important.
The phytochemical resveratrol, which is found in grape skin, appears to be responsible for the well-known protective effects in red wine and purple grape juice.
The plant sterols, including sitosterol, are also proving to be potent cholesterol fighters. Sitostanol, a derivative of sitosterol, is being used in new margarine products to lower cholesterol levels.

Protection against Stroke and Dementia

A healthy diet rich in fruits and vegetables and low in salt and saturated fats may significantly lower the risk for a first stroke. (The protective effects of diet on a second stroke are less clear.)

Vitamins. The effects of antioxidant vitamins on stroke, dementia, or both are being studied. Studies are conflicting, however. As is the case with many vitamin studies, consumption of vitamin-rich diets offer consistent benefits even when supplements do not.

Vitamin E. Studies in 2000 have suggested that high-dose supplements of vitamin E may protect against stroke in people with type 2 diabetes and men with high blood pressure. (One of the studies found no protection for men with normal blood pressure.) In another 2000 study, men who took vitamin E, C, or both for less than three or four years experienced no protection against dementia associated with stroke. However, men who took both for eight years had an 88% reduced risk for dementia from stroke. High doses of vitamin E may increase the risk for bleeding and therefore hemorrhagic stroke, a far less common form.
Vitamin C. In yet another 2000 study in Japan, individuals who consumed a vegetable-rich diet and had the highest blood levels of vitamin C enjoyed a significantly lower risk of all types of stroke compared to people who ate few vegetables per week. Supplements do not appear to offer any advantage.
B Vitamins. Vitamins B6, B12, and folic acid are important for the production of neurotransmitters, the chemical messengers in the brain that regulate mood and concentration. Deficiencies in these vitamins have been observed in people with depression and dementia and even in those who perform badly on tests. In one study, when subjects were deprived of B6, their memories deteriorated; when B6 was restored, their memories improved. (Large doses of B6, however, can damage nerves.) Studies have also suggested that people who have higher blood levels of folic acid have a lower than average risk for stroke.

Carotenoids. Some studies have reported a lower risk of stroke from beta carotene and lycopene. However, in one 2000 study comparing diets containing vitamin C and a number of carotenoids (beta carotene, lutein, lycopene, and zeaxanthin), only diets rich in beta carotene were protective.

Protection against Cancer

Many fresh fruits and vegetables contain chemicals that may fight many cancers, including lung, breast, colon, and prostate cancers. Examples of important cancer fighting foods include the following:

Cruciferous vegetables (eg, cabbage, Brussels sprouts, broccoli).
Tomatoes (which contain lycopene).
Carrots (which contain alpha carotene).

Any protective effects of vitamins or specific phytochemical against cancer, however, appear to depend on the cooperative effort among them. Individual supplements of any vitamin or food chemical have not as yet shown any benefits.

Vitamins. Because many cancers are thought to be initiated by the effects of oxygen-free radicals on DNA, the antioxidants A, C, and E and beta carotene have been intensively studied. To date, no individual supplements have offered any protection against cancer, and high doses may even be hazardous. [See Box Special Warning on Antioxidant Supplements]

Vitamin A, C, and E. Although supplements of vitamins A, C, and E appear to have no advantages, studies have reported an association between low blood levels of these antioxidant vitamins and a higher risk for cancer. And a 1999 study reported an association between high blood levels of vitamin E and a lower risk for lung cancer, particularly among nonsmokers. Certain natural forms of vitamin E, including tocotrienol (a compound found in unrefined palm oil) or vitamin E succinate (VES) may be more protective against certain cancers than alpha-dl tocopherol, the standard vitamin E supplement.
Vitamin D. Some studies have suggested that certain vitamin D compounds may inhibit certain cancer cells, specifically prostate cancer, from proliferating. More research is needed.
Folic acid and B12. These B vitamins convert the amino acid homocysteine to methionine, a substance that helps prevent cells from becoming malignant. Folic acid may provide some protection against cervical and colon cancer. One small study showed a reduction of lung cancer cells in smokers taking folic acid and vitamin B12, but the study was very small, of short duration, and other factors might have biased the results. Still another study reported that folic acid may reduce the risk for breast cancer among women who regularly drink alcohol. (In the study, folic acid had no other effect on breast cancer.)
A 2000 study reported that men with the lowest blood levels of vitamin C had a significantly higher risk for dying from cancer. Low levels of vitamin C did not appear to pose such risks in women.

Carotenoids. A number of studies have reported that fruits and vegetables rich in carotenoids are associated with protection against many cancers. Individual supplements, however, do not offer any advantage, and, in fact, there is some evidence that beta carotene increases the risk for lung cancer in smokers. One individual carotenoid, however, is provoking interest. Lycopene, found in tomatoes, may have particular value in protection against prostate, colon, lung, and bladder cancer.

Phytochemicals.

Isothiocyanates and sulforaphane found in cruciferous vegetables may block the effects of carcinogens and suppress tumor growth. Young sprouts of broccoli and cauliflower, compared to their mature counterparts, contain much higher levels of isothiocyanates. In one study, women with the highest consumption of cruciferous vegetables had a 24% lower risk of breast cancer than women with the lowest consumption.
Isoflavones are plant estrogens. They include daidzein, equol, and enterolactone, are found in soy beans, whole wheat, berries, and flax seed. They may help reduce the risk for certain hormone-stimulated cancers, such as breast and prostate, by replacing human estrogen with the benign plant estrogens they contain. They may also inhibit the proliferation of existing cancer cells. Much research has focused on soy. In general, Asian women have a lower incidence of reproductive and breast cancers as well as a higher intake of soy. A 2000 study of 120 Asian women reported an association between high levels of soy compounds in the urine and a lower risk for breast cancer, as much as 50% lower. The effects of phytoestrogens, however, in all cases are far from settled, however. One study reported that soy appeared to protect against breast and uterine cell proliferation in postmenopausal women who take high doses of estrogen replacement therapy. However, when combined with low doses of estrogen replacement therapy, soy caused breast cell proliferation. Other studies on phytoestrogens in black cohosh have observed cell proliferation in the uterus under certain circumstances. Some experts advise that until more is known about when or even if phytoestrogens protect against breast cancer, women who are on hormone replacement therapy and at risk for breast cancer should also avoid plant products with known high levels of phytoestrogens. Some evidence suggests the genistein in soy may have properties that are protective against lung cancer.
Flavonoids and polyphenols, including those found in apples, onions, tea, and red wine, are coming under scrutiny for possible cancer fighting properties. In one 24-year study, people who ate flavonoid-rich foods had a 20% lower risk for cancer in general. The polyphenols in green tea may be particularly protective.
Resveratrol, a phytochemical found in grapes, has been found to fight tumor promotion and progression in mice.
The organosulfur compounds found in the onion and garlic family may have very potent properties in suppressing or blocking carcinogenic substances. Studies indicate that people who regularly consume fresh or cooked garlic have about half the risk of developing stomach cancer and two thirds the risk of colorectal cancer as people who eat little or no garlic. One possible explanation for garlic's anti-cancer effect in the stomach is its antibacterial action against H. pylori , which can promote stomach cancer. Taking garlic supplements, however, did not offer these benefits.

Antioxidants and Chemotherapy

On a positive note, there is some evidence that antioxidants found in vitamins, carotenoids, and phytochemicals may enhance the anticancer effects of chemotherapy. In a 2000 study, patients with impaired antioxidant status were relatively unresponsive to chemotherapy, while those who maintained their antioxidant levels were better able to withstand the high stress caused by chemotherapy. A number of antioxidant nutrients studied have shown to have properties that may help reduce the side effects of chemotherapy or even enhance their anti-cancer activities. They include vitamins E and C, beta carotene, genistein and daidzein (isoflavones found in soy), and quercetin (found in red wine an purple grape juice).

Special Warning on High-Dose Antioxidant Supplements

Some studies are now suggesting that excessive use of antioxidant supplements may interfere with other nutrients or convert into pro-oxidants and become harmful. Of particular concern are studies that have found an increase in lung cancer and overall mortality rates among smokers who took beta carotene supplements. A 2000 study further reported a higher risk for cancer in male smokers who took multivitamins plus A, C, or E. In determining reasons for this disturbing effect, one animal study suggested that beta carotene increased enzymes in the lungs that actually promote cancerous changes. And, even more worrisome, in people with existing cancer, high doses of antioxidant vitamins, such as vitamin C or beta carotene, may actually protect cancer cells (just as they do healthy cells). Some evidence also exists that high doses of vitamin C may speed up atherosclerosis.

Protection against Infectious Diseases

Vitamins. A number of studies suggest some defense against infection:

A 1993 study found that older people who took a multivitamin had fewer sick days than those who did not.
One analysis of studies found that large doses of vitamin C reduced the duration of the common cold by 21%, and another found that it reduced the severity and length of respiratory infections in a group of ultramarathon athletes, who are normally at risk for these infections.
Fewer incidents of infectious diseases have been observed in people taking large supplements of vitamin E.
In a study of elderly people whose immune systems had deteriorated, B6 restored them to normal levels, and in those taking large doses, the immune response was close to that seen in young people. It was not clear from the study if vitamin B6 actually protected against disease, and it should be noted that large doses of this vitamin can cause nerve damage so should be taken only under advisement from a physician.
In studies in underdeveloped countries where immunization programs are limited and risks for infectious diseases are high, children with infectious diseases who were given vitamin A have lower mortality rates. Vitamin A supplements, however, are toxic in children in amounts close to normal adult doses and should never be given to children with normal diets.

Phytochemicals. Saponins extracted from ginseng and allicin (found in garlic) also have properties that boost the immune system. Both ginseng and garlic have long been traditionally used for their health benefits.

Carotenoids. Lycopene, found in tomatoes, appears to have properties that protect infection-fighting white blood cells.

Protection against Respiratory Disorders

Antioxidant Vitamins. Some people with exercise-induced asthma may benefit from taking vitamin C one hour before strenuous physical activity. Antioxidant vitamins, however, do not appear to reduce the risk of adult-onset asthma. Some evidence indicates that a low dietary intake of antioxidant nutrients could increase the risk for lung damage. Such nutrients should be obtained from fresh, deep green and yellow-orange fruits and vegetables.

Protection against Eye Disorders

Vitamins. Oxygen-free radicals play a role in cataract formation. Several studies report that the consumption of antioxidant-rich foods is associated with a decreased risk for cataracts. Vitamins E and C and the B vitamins niacin and riboflavin (vitamin B2) might protect against cataracts.

Carotenoids. Carotenoids, especially lutein (found in egg yolks and bright yellow vegetables) and zeaxanthin (found in eggs and dark, green vegetables), may be important in preventing macular degeneration, the most common cause of irreversible blindness in the elderly. According to some observational studies, diets rich in lutein and zeaxanthin may also reduce the risk of cataracts.

Protection against Skin Disorders and Wrinkles

A diet with plenty of whole grains, fresh fruits and vegetables, and the use of healthy oils (such as olive oil) may protect against oxidative stress in the skin.

Topical Antioxidants. There is some evidence that lotions and creams containing antioxidants may help protect the skin when applied before sun exposure. (They do not seem to provide benefit after exposure.) Studies vary on their effect and the following are some positive ones:

Studies suggest that topical vitamin E, particularly alpha tocopherol (a form of vitamin E) cream, decreases skin roughness, length of facial lines, and wrinkle depth. Studies on mice have also reported reductions in UV-induced skin cancer with its use.
Vitamin C, or ascorbic acid, is a potent antioxidant and large amounts appear to reduce skin swelling from sunlight, and long-term use may even promote collagen production. Vitamin C by itself is unstable, but products that solve the delivery problem are now available (including Cellex-C, Avon's Anew Formula C Treatment Capsules, and others).

Oral Antioxidants. Some research has been conducted on the effects on wrinkles using oral antioxidant supplements. One small study found that taking a combination of oral C and E supplements may help reduce sunburn reactions, although the protection is much less than from sunscreens. (Taking the vitamins singly does not appear to have the same effect.)

Phytochemicals. The following foods and phytochemicals may be skin protective:

Both green tea and ginger appear to have properties that may provide some protection against skin cancer. Green tea skin care products are now available. Scientific studies will be needed to learn if they are actually beneficial.
The substance silymarin, found in the milk thistle family (which includes artichokes), may inhibit UVB-promoted cancers in animals.
In one interesting study, eating garlic protected animals very effectively against UVB damage by interfering with urocanic acid in the skin. Whether these results may apply to humans (and what quantities of garlic might be beneficial) is still unknown.

Protection against Osteoporosis

Studies suggest that diets rich in fresh fruits and vegetables (which include those high in potassium and magnesium) reduce elimination of calcium from the body and help preserve bones.

Vitamins and Bones.

Vitamin D. Vitamin D is the essential companion to calcium in maintaining strong bones. Supplements may be needed for people who have poor exposure to sunlight. It should be noted that diet supplies most people's need and high amounts of vitamin D can be toxic.
Vitamin K. Studies suggest that vitamin K has properties that protect bone and prevent fracture. Vitamin K2 (menatetrenone), a form of vitamin K, is proving to prevent fractures in people with osteoporosis. Intestinal bacteria produce vitamin K, and the vitamin is found in leafy vegetables, so deficiencies are rare. Vitamin K affects blood clotting, and supplements are not recommended without specific physician instruction.
Vitamin B12. One study reported that in people with osteoporosis and pernicious anemia, taking vitamin B12 (which is used to treat the anemia) also increased bone density.
Vitamin C and E. There has been some indication of a positive association between vitamin C and E intake and bone density, although evidence proving actual benefits is weak.
Vitamin A. A Swedish study indicated that high amounts of dietary vitamin A might reduce bone density. (A form of vitamin A, retinoic acid, has been found to stimulate bone break down.)

Soy and Isoflavones. Studies are suggesting that isoflavones-rich soy products may actually improve bone density in postmenopausal women. Tofu prepared with calcium may be particularly beneficial; 3 ounces supply 60% of daily calcium requirements. Some experts recommend 25 to 45 milligrams of isoflavones a day. Soy powders, soluble in juice or milk, that list amounts of isoflavones per serving are now available in health food stores. To date, evidence suggests that supplements derived from soy do not provide the benefits of the whole protein.

Gallstones

Ascorbic acid (vitamin C) appears to help break cholesterol down in bile. Vitamin C deficiencies have been associated with a higher risk for gallstones. One 2000 study, which confirmed some previous ones, reported that supplements were associated with a reduced risk for gallbladder disease in women. (Vitamin C had no effect in men, however.)

Menstrual Disorders

Vitamin B6. Limited clinical evidence suggests that vitamin B6 may be beneficial in reducing premenstrual symptoms, including depression. Typically, women take 100 mg per day, although one study suggested that a lower dose (50 mg) may have the same effect.

Vitamin B1. One study reported relief from menstrual pain using vitamin B1 (thiamin).

Vitamin E. Several randomized controlled trials have shown that vitamin E significantly improves both physical and emotional symptoms.

WHO SHOULD TAKE VITAMIN SUPPLEMENTS?

About 30% of Americans take at least one vitamin or mineral supplement daily. In a large study that examined the death rates of 11,000 people, however, there was no difference in mortality rate between those who took vitamin supplements and those who didn't. If a diet is healthy, most people do not need vitamins, but there are some exceptions.

Pregnant and Breast-Feeding Women

Women who are pregnant or who are breast-feeding generally need additional vitamins. The B vitamins are particularly important. Folic acid reduces the risk for neural tube defects and possibly facial abnormalities, such as cleft palate. Multivitamins that contain folic acid also appear to be somewhat protective. Taking extra folic acid plus multivitamin supplements (which have additional benefits) and starting them before a women actually becomes pregnant is the optimal approach.

Folate levels from even healthy diets may not be protective enough for pregnant women and supplements are needed. Requirements are as follows:

The RDA for folic acid prior to conception and during pregnancy is 400 mcg.
During breast feeding between 260 and 280 mcg is recommended.

Other vitamins that may have some value for pregnant women are as follows:

Choline, another vitamin B, is also essential for pregnant (450 mg) and nursing women (550 mg).
Vitamin B6 may help improve morning sickness.
One study also suggested that if pregnant women took vitamin K supplements, their infants might not need the required injection of this vitamin after birth, but supplements of vitamin K during pregnancy are not currently recommended.
Some women have low vitamin A reserves in their liver. It is important to note, however, that too much vitamin A significantly increases the risk for birth defects. Daily amounts of 10,000 IU of vitamin A in supplements and food (an amount not far above the RDA level) can pose a danger. Experts recommend that pregnant women take in no more than 8,000 IU per day and avoid eating liver.

Infants and Children

Infants who are breast fed by healthy mothers receive enough vitamins except, in some cases, vitamins K and D. Human milk has low levels of K, and the newborn's immature intestinal tract may not produce enough of the baby's own supply. Most babies are given an injection of this vitamin at birth. Infants being breast fed by malnourished women or those who lack sufficient exposure to sunlight may be deficient in vitamin D. In these cases, supplements of 200 to 300 IU are recommended. Formulas are required to contain sufficient vitamins and minerals. One study suggests that vitamin supplements for infants under one year of age may help protect them from developing type I diabetes later on. Past infancy, most American children receive all the vitamins they need from their diet unless they are living in severely deprived circumstances.

Smokers

Smoking interferes with absorption of a number of vitamins, importantly vitamin C. In fact, in one study nearly 25% of female smokers and 31% of male smokers were deficient in vitamin C. Folic acid supplements may be important for all smokers. Taking high doses of antioxidant vitamins, however, may actually be harmful in smokers, especially beta carotene. Instead of taking supplements, most smokers should be sure their diets are rich in fresh fruits and vegetables and whole grains.

Alcoholics

Alcoholics often suffer from multiple vitamin deficiencies. The most dangerous deficiencies are from vitamins B1 (thiamin), folic acid, B6 (pyridoxine), B2 (riboflavin), and vitamin C.

Dieters and Vegetarians

People on weight-reduction diets with less than 1,000 calories a day should probably take a multivitamin and should also check regularly with a physician. Vegetarians who do not eat dairy or meat products may need riboflavin, vitamin B12, and vitamin D supplements. One study reported that adolescents who had been on macrobiotic diets before age six and were deficient in vitamin B12 scored lower on psychologic tests. Those who eat eggs and dairy products need only watch their iron levels.

Older Adults

Deficiencies of vitamins and important minerals have been observed in almost a third of elderly people. Often their dietary habits slip and they fail to eat balanced meals regularly. Multiple drug regimens may prevent absorption of some vitamins. Elderly people, particularly if they are not exposed to sunlight, may be deficient in vitamin D. They also may have low levels of vitamins B6, folic acid, and B12. (Older adults showing signs of dementia should be checked for B12 deficiencies as well as other disorders causing mental disturbances.) One study reported that the immune systems of elderly people may benefit from higher levels of vitamin E than the daily recommended dosage. It should be noted, however, that metabolism slows down as a person ages, and in elderly people it takes the liver longer to eliminate drugs and vitamins from the body. The effect of some vitamin supplements, therefore, may be intensified; dosage levels of vitamin A, for instance, which might be harmless in a younger adult, could be toxic in an elderly patient. Nevertheless, experts are increasingly recommending extra vitamin and mineral supplements for older people.

WHAT ARE IMPORTANT FOODS?

Evidence increasingly suggests that a varied diet, not individual food chemicals, is essential for basic health and a longer life. Such diets are rich in fresh fruits and vegetables and whole grains, and low in saturated fats.

Some Examples of Healthy Foods

Foods	Phytochemicals and Carotenoids	Vitamins and other valuable food components	Benefits
Apples	Flavonoids		May have activity against certain cancers (lung). Also may help maintain healthy cholesterol.
Beans	Flavonoids	Folate, iron, potassium, and zinc.	Some experts believe beans are the perfect food.
Berries, all kinds of dark colored	Ellegic Acid	Vitamin C, minerals	May protect the aging brain. (In one study blueberries were most effective).
Broccoli (also kale, Brussels sprouts, cauliflower)	Flavonoids, isothiocyanates, lutein, beta and alpha carotene	Vitamin C, folate, fiber, and selenium	Anticancer properties. Protective against heart disease and stroke.
Carrots and other bright yellow vegetables	Lutein, beta carotene and other provitamin A carotenoids.	Vitamin A (converted from carotenoids), Vitamin C	Protects eyes, lungs. (Cooking carrots may increases the potency of food nutrients.)
Eggs	lutein	Many B vitamins, vitamin A, vitamin D	Although egg yolks are high in cholesterol, very little of it has a negative effect on people with normal levels. And the health benefits of eggs are now known to be very high. (People with diabetes or those with high cholesterol should restrict eggs, however.)
Fish, oily (mackerel, salmon, sardines)		Vitamin B3, B12. Essential fatty acids, selenium	Heart and brain protective.
Garlic	Allium (organosulfurs)		Possibly protective against certain cancers, heart diseases, and infection. Heating garlic can reduce benefits. Allowing crushed fresh garlic to stand 10 minutes before heating, however, may preserve beneficial chemicals while cooking.
Ginger	Zingiberaceae		Cancer fighting properties.
Grains (whole)	Lignans (phytoestrogens)	Vitamin B, Selenium (important antioxidant mineral), fiber, folate	May help reduce the ability of cancer cells to invade health tissue.
Grapes, including purple grape juice, and red wine	Flavonoids, (resveratrol, quercetin and catechin)		Fight heart disease and cancer.
Nuts		Vitamin E, Vitamin B1, Essential fatty acids, folate	Protects the heart and may help prevent stroke.
Onions	Flavonoids, allium (organosulfurs)		May have activity against certain cancers (lung).
Oranges	Monoterpenes	Vitamin C, folate, potassium	Many health benefits. Increases HDL levels.
Potatoes (Sweet)		Vitamin C, vitamin E, vitamin A	Many health benefits.
Soy	Isoflavones (phytoestrogens), flavonoids, phytosterol, phytate, saponins		May have effects similar to estrogen, including maintaining bone and benefiting the heart. May also be protective against prostate cancer and possibly other cancers. More studies are needed. (Note: of some concern is one study reporting more mental decline in people who consume greater amounts of tofu.)
Spinach and other dark green leafy vegetables	Zeaxanthin, Beta carotene,	Vitamin C, folate, Vitamin A (converted from carotenoids)	Protects lungs and brain.
Tea (Green tea has reported best benefits)	Flavonoids		Cancer fighting properties, particularly in green tea. Black tea does not appear to have these particular benefits. Both black and green tea are heart protective and may protect against stroke.
Tomatoes	Lycopene, Flavonoids	Vitamin C, biotin, minerals	Studies link to reductions in prostate and other cancers. Infection fighters.

WHERE ELSE CAN VITAMIN INFORMATION BE OBTAINED?

Office of Dietary Supplements, National Institutes of Health, Building 31, Room 1B29, 31 Center Drive, MSC 2086, Bethesda, Maryland 20892-2086.

Call: (301-435-2920) or on the Internet (http://dietary-supplements.info.nih.gov/)

Other Government Sites:

The Food and Nutrition Information Center (FNIC) (http://www.nal.usda.gov/fnic/)

Food and Drug Association (http://vm.cfsan.fda.gov/)

The American Dietetic Association, 216 W. Jackson Blvd., Chicago, IL 60606-6995.

Call (312-899-0040) or fax (312- 899-1979) or on the Internet (http://www.eatright.org/)

Nutrient Data Laboratory, US Department of Agriculture, Aricultural Research Service, Beltsville Human Nutrition Research Center, 10300 Baltimore Avenue, Building 005, Room 197, BARC-West, Beltville, MD 20705-2350. Call (301-504-0632) or on the Internet (http://www.nal.usda.gov/fnic/foodcomp/)

Provides information on amounts of specific nutrients in foods.

Food and Drug Administration, HFI-40, Rockville, MD 20857

On the Internet (http://www.fda.gov)

American Council on Science and Health, 1995 Broadway Second Floor, New York, NY 10023-5860.

Call (212-362-7044) or on the Internet (http://www.acsh.org)

This organization provides literature on a range of health topics, including vitamins. Booklets cost $3.95 each. Request Vitamins and Minerals: Does the Evidence Justify Supplements?

American Institute for Cancer Research (AICR), American Institute for Cancer Research, 1759 R Street N.W., Washington, D.C. 20009. Call (1-800-843-8114) or (202-328-7744) in Washington, D.C.For dietary recommendations: (http://www.aicr.org) or email:

Useful Internet Sites Internet

(http://www4.nas.edu/IOM/IOMHome.nsf/Pages/IOM+Programs)

University of Illinois website on Functional Foods (http://www.ag.uiuc.edu/~ffh/)

Excellent site sponsored by SmithKline Beechum for obtaining vitamins and nutrients contained in specific foods. (http://www.calciuminfo.com/)

Complete reports by the Institute of Medicine on recommendations for specific nutrients:

Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoid (http://www.nap.edu/books/0309069351/html/)

Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium,

Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc

(http://www.nap.edu/books/0309072794/html/)

ConsumerLab.com - at http://www.consumerlab.com, is a subscription-based web site that provides the results of independent testing of nutritional supplements' contents and quality.

ABOUT WELL-CONNECTED

Well-Connected reports are written and updated by experienced medical writers and reviewed and edited by the in-house editors and a board of physicians, including faculty at Harvard Medical School and Massachusetts General Hospital. The reports are distinguished from other information sources available to patients and health care consumers by their quality, detail of information, and currency. These reports are not intended as a substitute for medical professional help or advice but are to be used only as an aid in understanding current medical knowledge. A physician should always be consulted for any health problem or medical condition. The reports may not be copied without the express permission of the publisher.

Board of Editors

Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

Stephen A. Cannistra, MD, Oncology, Associate Professor of Medicine, Harvard Medical School; Director, Gynecologic Medical Oncology, Beth Israel Deaconess Medical Center

Masha J. Etkin, MD, PhD, Gynecology, Harvard Medical School; Physician, Massachusetts General Hospital

John E. Godine, MD, PhD, Metabolism, Harvard Medical School; Associate Physician, Massachusetts General Hospital

Edwin Huang, MD, Gynecology, Harvard Medical School, Physician, Massachusetts General Hospital

Daniel Heller, MD, Pediatrics, Harvard Medical School; Associate Pediatrician, Massachusetts General Hospital; Active Staff, Children's Hospital

Paul C. Shellito, MD, Surgery, Harvard Medical School; Associate Visiting Surgeon, Massachusetts General Hospital

Theodore A. Stern, MD, Psychiatry, Harvard Medical School; Psychiatrist and Chief, Psychiatric Consultation Service, Massachusetts General Hospital

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