<<<... 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. Although supplements can do us a world of good, remember that just because a product calls itself a vitamin or supplement, that doesn’t necessarily mean it’s good for you. Synthetic vitamins can actually be dangerous, so it’s important to be educated about them.