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About 40 percent of Americans take at least one vitamin or mineral supplement daily and another 20 percent take them occasionally. Taking vitamins and minerals seems to fall within a gray area — giving your body what it needs by taking supplements certainly benefits you in every way, but knowing how to assess that need is often difficult. Without testing, it’s hard to say which vitamins and minerals you personally need. But these general guidelines apply if you’re in one of these special needs groups:

Pregnant and breast-feeding women
Women who are pregnant or breast-feeding generally need additional vitamins, and the B vitamins are particularly important. Folic acid reduces the risk for neural tube defects and possibly facial abnormalities, such as cleft palate, in newborns. Multivitamins also appear to protect against certain congenital heart defects. In order to be protective, however, both folic acid and multivitamin supplements must be taken before a woman actually becomes pregnant. Folate levels, even in a healthy diet, may not be protective enough for pregnant women, and so supplements are needed. The RDA for folic acid prior to conception and during pregnancy is 400 mcg. During breast-feeding, between 260 and 280 mcg is recommended. Choline, another B vitamin, is also essential for pregnant and nursing women — 450 mg during pregnancy and 550 when breast-feeding. Vitamin B6 may help improve morning sickness. Although one study suggested that if pregnant women take vitamin K supplements, their infants might not need the required injection of this vitamin after birth, supplements of vitamin K during pregnancy are not currently recommended.

Some women have low vitamin A reserves in their livers, but it is important to note 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 to supply sufficient amounts to the baby. Most babies are given an injection of vitamin K at birth. Infants who are breast-fed by malnourished women or by those who lacked sufficient exposure to sunlight may be deficient in vitamin D. In these cases, supplements of 200-300 IU are recommended. Formulas are required to contain sufficient vitamins and minerals. One study suggests that when infants under 1 year of age take vitamin supplements it may help protect them from developing Type I diabetes later in life. Beyond infancy, most American children receive all the vitamins they need from their diets, unless they are living in severely deprived circumstances.

Smokers
Smoking interferes with absorption of a number of vitamins; most importantly, vitamin C. Folic acid supplements may be important for all smokers. When smokers take high doses of antioxidant vitamins, however, it may actually be harmful, 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 vitamin B1 (thiamin), folic acid, vitamin B6 (pyridoxine), vitamin B2 (riboflavin) and vitamin C.

Dieters and vegetarians
People on weight-reduction diets of fewer than 1,000 calories per day should probably take multivitamins 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. 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 one-third of elderly people, who often fail to eat balanced meals regularly. Multiple drug regimens that are prescribed for some elderly people may prevent absorption of some vitamins. The elderly, particularly if they are not exposed to sunlight, may be deficient in vitamin D. They also may have low levels of vitamin B6, folic acid and vitamin B12. (Older adults showing signs of dementia should be checked for vitamin B12 deficiencies as well as other disorders that cause mental disturbances.)

One study reported that the immune systems of elderly people might benefit from vitamin E in levels higher than the daily recommended dosage. It should be noted, however, that metabolism slows down as a person ages, and in elderly people it takes longer for the liver 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 vitamins and minerals for older people.

Photo by Alexander Kalina