Vitamin E
Vitamin E is actually a family of eight related compounds called tocopherols. Alpha-tocopherol, the type most abundant in foods, also dominates in vitamin-E supplements. (The other leading types are beta-, gamma-, and delta-tocopherol.) The vitamin is believed to function chiefly as an antioxidant, but studies show that it also strengthens immunity in the elderly.
The foods richest in vitamin E are vegetable oils, margarines, meats, legumes, nuts, seeds, and unprocessed cereal grains.
Since vitamin E is fat-soluble, the body can store it for long periods. Deficiency is rare, and often tied to diseases that impair the body's ability to absorb fat, such as cystic fibrosis, chronic cholestatic liver disease, short-bowel syndrome, and the rare, inherited disorder called abetalipoproteinemia. Symptoms of a deficiency include muscle weakness, poor coordination, and hemolysis.
High intake of natural vitamin E from foods is not known to be harmful. But because they believe vitamin E cuts their risk of heart disease and prostate cancer (see below), many people, including nutrition experts, take supplements as large as 20 times the Recommended Dietary Allowance. Side effects from doses up to 800 milligrams per day are generally rare and mild. (The most common is stomach upset.) Higher intake can interfere with blood clotting and cause headache, fatigue, diarrhea, nausea, muscle cramps or weakness, blurred vision, and reproductive problems.
Vitamin E and Cancer*
Of the four leading cancers--breast, lung, colon, and prostate--only prostate cancer seems to be connected to vitamin-E intake. Several studies have shown lower incidence and fewer deaths from prostate cancer among smokers who take vitamin-E supplements. In the general population, however, such a link has not been proven.
Vitamin E and Heart Disease*
Although millions of people take vitamin-E supplements to prevent or treat heart disease, the scientific evidence is mixed. In general, the largest studies show that:
In the general population:
· Heart disease is significantly less common among people who take vitamin-E supplements.
· Heart disease is not less common among people who get extra vitamin E from foods alone.
Among patients already diagnosed with heart disease:
· Getting extra vitamin E does not improve outcomes.
*
Our latest source for the cancer and heart-disease summaries is a review of more than 150 scientific papers, "Vitamins for Chronic Disease Prevention in Adults," published by Drs. Kathleen M. Fairfield and Robert H. Fletcher in the June 19, 2002, Journal of the American Medical Association (JAMA). Reprints can be downloaded (for a fee) from the JAMA Web site at
www.jama.ama-assn.org.
Your Daily Allowance
The Food and Nutrition Board's (FNB's) Recommended Dietary Allowance (RDA) is officially cited in milligrams of alpha-tocopherol or its equivalent in other tocopherols. In April 2000 the FNB raised the RDA for men by 50 percent and nearly doubled the RDA for women. The new RDA is 15 milligrams for both sexes, including pregnant women. For lactating mothers it is 19 milligrams.
(Because vitamin-E supplements can interfere with blood clotting, patients on anticoagulant therapy should be monitored by a doctor when taking them.)
Upper Limit
In April 2000, for the first time, the FNB also set a Tolerable Upper Intake Level (UL) for vitamin E. The UL does not apply to vitamin E that occurs naturally in foods, but to any form of alpha-tocopherol obtained from supplements, fortified foods, or a combination of the two. For people age 14 to 18 it is 1200 IU; for people 19 or older, 1500 IU. (Be careful: if you're measuring vitamin E in milligrams instead of IU, these upper limits are 800 and 1000, respectively.) Getting more than the UL may be harmful to your health.
(CAUTION: You may need to observe lower limits if you take supplements containing "dl-alpha-tocopherol," a synthetic form of the vitamin. This form's upper limit is only 1100 IU for people 19 or older and 900 IU for those 14** to 18. The natural form, "d-alpha-tocopherol," differs in name by only one character, so check the label carefully.)