Safe Doses of Vitamins

Vitamins are a crucial part of healthy growth and development, and are especially important for vegans and vegetarians, pregnant and nursing women and some health conditions. However, excessive vitamin intake may cause unpleasant side effects. Consult your doctor before purchasing any new vitamin for regular use, and research the vitamin for safety and effectiveness.

Recommended Dosage

Before you purchase a new vitamin supplement, always research the recommended daily value, or RDA, for the product. RDA is "the average daily dietary intake level; the amount sufficient to meet the nutrient requirements of nearly all healthy individuals in a group." RDA varies based on your age and gender. Children, infants, pregnant women and lactating women have different RDA for most vitamins. For example, although non-lactating women age 19 and older only need 700 mcg of vitamin A, breastfeeding women need 1,300 mcg.

Megadoses

Many vitamin supplements provide megadoses of vitamins, which far exceed the RDA. According to Bruce N. Ames, a biochemist at the University of California Berkeley, megadoses of B vitamins may help prevent genetic conditions and decrease the effects of aging. There is a belief that other vitamins, such as vitamin C, can prevent colds when taken in megadoses. However, research shows that megadoses of vitamins may not always be effective. A 2001 study by researchers at the Australian National University demonstrated that vitamin C megadoses did not reduce cold duration or severity when compared with doses below the RDA.

Danger

Not only are megadoses of vitamins often ineffective; they may also be dangerous in some cases. Vitamin A toxicity, or hypervitaminosis A, results from taking excessive doses of vitamin A, and may cause blurred vision, bone pain, change in consciousness, decreased appetite, vomiting, weight gain and liver damage. Vitamin B-3, or niacin, may also cause serious symptoms when taken in megadoses, such as rapid heartbeat, itching, vomiting, diarrhea and abdominal pain. Therefore, you should only take vitamin megadoses with your doctor's recommendation.

Supplements vs. Food Sources

Food sources are the best way to obtain your vitamins. Food provides a more balanced array of vitamins, as well as other nutrients like minerals and fiber. It also is less likely to cause overdose. Unlike many synthetic vitamins, food sources tend to contain small amounts of vitamins, as well as fats and carbohydrates, which make vitamins easier to digest. For best results, monitor your diet carefully and always consult your doctor before you decide whether to take a supplement.