Debate surrounds vitamin E
Despite more than 80 years of extensive vitamin E research, exactly how much vitamin E is best for good health still remains controversial. Some estimates indicate that more than 90 percent of American adults do not consume adequate vitamin E in their diets. Consequently, reports of decreased chronic disease in people who take supplemental vitamin E is not surprising. Unfortunately, many high-quality studies also report increased disease risks with vitamin E supplementation.
Question: What are the functions of vitamin E?
Answer: Vitamin E is best known for its generalized antioxidant function. In other words, vitamin E protects cells from the damage caused by the daily wear and tear of the body's normal chemical reactions.
Vitamin E also plays a role in the immune system and DNA repair. This vitamin might also be protective in some types of cancers such as prostate cancer. Vitamin E also appears to decrease the sticking of platelets to the walls of arteries and veins, potentially providing cardiovascular protection and decreasing the overall risk of chronic disease.
Q: How much vitamin E is recommended?
A: Vitamin E is a fat-soluble vitamin that exists in eight different forms with slightly different functions and strengths. The synthetic form is only about half as active as the natural form. Currently the adult daily recommended dietary intake of vitamin E is 22 International Units, if consumed from natural foods. Some researchers recommend 100 to 150 IUs, especially for those with fat-absorption problems.
Because vitamin E functions in concert with other antioxidants like vitamin C, beta-carotene and selenium- dependent enzymes, an individual's intake of these other antioxidants likely affects the minimum amount of vitamin E needed. For example, low vitamin C intake can increase vitamin E needs.
Q: Can a person get too much vitamin E?
A: Yes. Although the upper limit set by the Institute of Medicine for vitamin E is 1,100 IU of synthetic vitamin E or 1,500 IU of natural vitamin E, other researchers have reported problems above 400 IUs. Because vitamin E can interfere with normal blood clotting, high intake increases the risk of internal bleeding. If this happens in the brain, it can cause a stroke. This risk is greater when high dose vitamin E is combined with aspirin, anticoagulant drugs or vitamin K deficiency.
Q: What are good natural sources of vitamin E?
A: Foods considered good sources of vitamin E include vegetable oils, nuts and green leafy vegetables. Fortified cereals also can be a good source of vitamin E, but read the labels.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S. are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dr. Dobbs also works with University Health Services.