Vitamins C and E

Antioxidant vitamins C and E play an important and complex role in human health. These nutrients, which can be obtained from both foods and dietary supplements, protect cells from the damaging effects of free radicals and may also help prevent and treat certain diseases. However, taking large doses of antioxidant vitamins provides no proven health benefits and may even be hazardous to health.

Benefits of Vitamin C

Vitamin C, in addition to its antioxidant properties, is necessary for the production of collagen tissue and plays an important role in immune function, according to the National Institutes of Health (NIH). Vitamin C, also called ascorbic acid, is also involved in protein metabolism and aids the absorption of iron in vegetables, reports the NIH. Vitamin C deficiency leads to scurvy, which, left untreated, can be fatal.

Vitamin C: Dosage and Sources

According to the Harvard School of Public Health (HSPH), the Institute of Medicine's (IOM) current recommended dietary intake (RDI) for vitamin C is 90 mg for men and 75 mg for women, though smokers should add 35 mg to these amounts. It is safe to take up to 2 g of vitamin C daily. In addition to dietary supplements, according to the HSPH, vitamin C can be found in citrus fruits and juices, red and green peppers, broccoli, berries, tomatoes and spinach. Certain foods, including breakfast cereal, are also fortified with vitamin C.

Benefits of Vitamin E

Like vitamin C, vitamin E (also called alpha-tocopherol) has antioxidant properties that scientists are studying, as of 2010, to determine whether they may prevent chronic diseases associated with free radicals, including cancer, according to the NIH. Vitamin E is involved in immune function and metabolic processes and may also prevent blood clots and coronary heart disease, reports the NIH. Vitamin E deficiency is rare in healthy people, according to the NIH, but may result in serious health problems including nerve damage and degeneration of the retina that can lead to blindness.

Vitamin E: Dosage and Sources

The IOM's RDI for vitamin E is 15 mg, which equates to 22 international units (IU) from natural-source vitamin E or 33 IUs of the synthetic form, according to the HSPH. However, reports the HSPH, as of 2010, scientists are reevaluating vitamin E intake guidelines and preliminarily finding that intake of up to 10 times that of the current RDI may be acceptable. Dosages exceeding 1,000 mg are not considered safe, according to the HSPH. Good sources of vitamin E in food include almonds, sunflower seeds, sunflower and safflower oil, peanut butter and dark leafy greens.

Antioxidant Misconceptions

According to the HSPH, despite abundant evidence that antioxidant-rich foods fight disease, as of 2010, clinical trials evaluating the disease-fighting qualities of high-dose antioxidant supplements --- including vitamins C and E --- have produced mostly inconclusive results thus far. Furthermore, according to the NIH, some studies link megadoses of vitamin E to increased risk of death. Rather than taking megadose supplements of antioxidant vitamins, the HSPH recommends taking a daily multivitamin and eating whole foods that are naturally rich in antioxidants.