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 cancers¾breast, lung, colon, and prostate¾only 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.
Studies continue, however. For the latest news, visit Diet Power's News/Update page.
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
Diet Power sets your Personal Daily Allowance (PDA) of vitamin E at the Food and Nutrition Board's (FNB's) Recommended Dietary Allowance (RDA), which 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.
Instead of milligrams, however, Diet Power always cites vitamin E in International Units, since those are most often used on food labels. Converted to IUs, the new RDAs are 22 for males and females (including pregnant women) and 28 for nursing mothers.
(Because vitamin-E supplements can interfere with blood clotting, patients on anticoagulant therapy should be monitored by a doctor when taking them.)
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.)
** Please remember that Diet Power is not designed for people under 15.
If a label cites vitamin E in milligrams¼
¼you can convert them to IUs. See International Units of Vitamin E.
Revising Your Allowance
Diet Power automatically sets your Personal Daily Allowance of vitamin E when you enroll in the program, but if your doctor recommends a different allowance, you can change it. See Personal Daily Allowances, Editing Your.)
Color Coding of This Nutrient
The vitamin-E bar in your personal Nutrient History is:
· blue for "good" if you've logged 100 to 200 percent of your PDA
· red for "bad" if you've logged less than 100 percent of your PDA or more than the Tolerable Upper Intake Level (UL)
· yellow for "caution" if you've logged more than 200 percent of your PDA
· missing if you've logged no vitamin E.
In the nutrient profile of a food or recipe, the vitamin-E bar is:
· green for "good" if getting your entire PDA of calories from this item would give you more than 150 percent of your PDA of vitamin E
· magenta for "bad" if getting all your calories from the item would give you less than 50 percent of your PDA of vitamin E
· blue for "neutral" otherwise
· missing if the amount of vitamin E is either zero or (when the term Vitamin E is grayed out) unknown.
How Complete Are Diet Power's Vitamin-E Readings?
For the 8500 generic items in the Food Dictionary: not terribly complete. About 30 percent list their vitamin-E content as "unknown."
For the 2500 chain-restaurant items: totally incomplete. All list vitamin E as "unknown."
For all 11,000 items combined: not terribly complete. About 44 percent list vitamin E as "unknown."
These figures mean that your Nutrient History will almost always underreport your intake of vitamin E, unless you log mostly foods with vitamin-E readings that you've added to the dictionary yourself.
To see whether a particular food has a vitamin-E reading, open the Food Dictionary and check the food's nutrient profile. If you find a question mark beside "Vitamin E," it means the amount is unknown. (To see all foods with unknown vitamin-E readings, click the dictionary's PowerFoods tab and sort the foods by vitamin-E power; then scroll toward the bottom of the list until you see foods with question marks in the "Power Rating" column.)
Vitamin E on Food Labels
Most food labels are not required to report vitamin-E content, but some do. They may cite the amount in International Units (IU), in milligrams of alpha-tocopherol, or in percent of Daily Value.
The Daily Value for vitamin E is 30 International Units, or 22 milligrams of alpha-tocopherol. (Why so much higher than the RDAs? Because all Daily Values are based on the RDAs of 1968, which for some nutrients were different from today's.) The Daily Value is not necessarily right for you, however¾it's a rough estimate meant to cover most of the U.S. population. (Remember, too, that the Daily Value does not yet reflect the April 2000 increase in this vitamin's RDA. See above.)
For more on label regulations, see Labels, Food.