Can Vitamin E Prevent Heart Disease?

Nutrition Forum, July, 1999 by Beth Fontenot

To E or not to E?

Some of the most interesting nutrition research in recent years has produced preliminary evidence that large doses of vitamin E may reduce the occurrence of heart attacks. As a result, vitamin E has received a great deal of media attention, prompting consumers to spend $300 million a year on vitamin E supplements. A few health and nutrition experts are ready to jump on the bandwagon and recommend supplementation, but others are asking whether the evidence really warrants such a move.

Judging by sales, vitamin E is one of the most sought-after dietary supplement among Americans. The nutrient is popular, it seems, even among professionals.

And no wonder. The claims for the nutrient's benefits are prevalent and appealing. "Health-food" literature and the media would have us believe that taking vitamin E will prevent arthritis, cataracts, stroke, diabetes, cancer, and heart disease. In addition, it's supposed to boost the immune system, ease symptoms of premenstrual syndrome, delay symptoms of Alzheimer's disease, and protect the body from aging.

Vitamin E Basics

Vitamin E was discovered in the 1920s when rats fed a basic diet became unable to reproduce viable offspring but were cured when given tocopherol, a substance that had been isolated from vegetable oils. In fact, the term "tocopherol" comes from Greek words meaning "to bear offspring." Vitamin E became the name given to a group of eight fat-soluble compounds--four tocopherols (designated alpha, beta, gamma, and delta) and four tocotrienols (designated with the same Greek letters). It was not until 1966 that vitamin E was considered essential for humans.

All of these compounds have different degrees of biological activity. The most active form of the vitamin is the "d" isomer of alpha-tocopherol, which is found in many supplements. Recent research has indicated that other forms, such as gamma-tocopherol, may also be important to the body. Though gamma-tocopherol has only one-tenth the biological activity of alpha-tocopherol, it is more widely distributed in foods. It's found in foods such as sunflower seeds, almonds, and wheat germ.

Vitamin E requires the presence of fats and bile in the gut to be absorbed. The degree to which vitamin E is absorbed by the body is dependent on the total absorption of dietary fat. Absorption can be as high as 70%. However, when taken in doses well above the Recommended Dietary Allowance (RDA), the absorption rate of vitamin E drops to less than 10%. Vitamin E travels through the body by way of chylomicrons and other lipoproteins, and it is distributed to almost all tissues in the body. It is most concentrated in tissues containing an abundance of fatty acids, such as cell membranes.

The primary function of vitamin E appears to be to act as an antioxidant. When incorporated into the lipid portion of cell membranes and carrier molecules, it protects these structures from toxic compounds, heavy metals, drugs, radiation, and free radicals. It also appears to protect cholesterol from oxidative damage.

The recommended intake for vitamin E is expressed in alpha-tocopherol equivalents ([Alpha]-TE). One [Alpha]-TE is equal to 1 mg of alpha-tocopherol. Vitamin supplement labels usually express vitamin E content in IUs (international units). One IU is equal to 1 mg of synthetic vitamin E or about 0.74 mg of natural [Alpha]-tocopherol. The current RDA for vitamin E is 10 mg for men (15 IU) and 8 mg (12 IU) for women. The RDA can be met with a tablespoon of corn oil.

Since many people medicate themselves with large amounts of vitamin E, it is fortunate that its toxicity is relatively low. However, the known toxicity of the other fat-soluble vitamins suggests that caution should be taken with long-term megadoses of vitamin E. High intakes of vitamin E can interfere with intestinal absorption of vitamins A and K. And at dosages exceeding 1,000 mg per day, vitamin E has been shown to enhance the effects of Coumadin therapy and to be antagonistic to the blood-clotting action of vitamin K.

Vitamin E and Head Disease

The oxidation of lipoproteins appears to play an important role in the development of atherosclerosis, the disease process that leads to heart attacks as well as strokes. Considerable evidence exists that antioxidant vitamins from both the diet and from supplements may prevent lipoprotein oxidation and its biological effects in the body. The strongest evidence seems to be for vitamin E.

Support for the role of antioxidant vitamins in heart disease prevention has come from observational studies, particularly two cohort studies that were published in 1993. In the first study, the Nurses' Health Study, the researchers concluded that among over 85,000 middle-aged women in the study, there was a 40% reduced risk of coronary artery disease for those who took vitamin E supplements compared to those who did not (N Engl J Med 1993;328: 1444-9). The second study, the Health Professionals Follow-up Study, involved over 39,000 males and provided evidence of a significant association between a high intake of vitamin E from supplements and a lower risk of heart disease (N Engl J Med 1993; 328:1450-1456).