Some recent studies linking vitamin E to the prevention of heart disease take another step in reinforcing the healthful image of the Mediterranean diet.
What still is not clear is just how vitamin E works, what form is the most effective and how much people need for the optimal health benefits.
Some experts believe the fat-soluble antioxidant found in olive oil, seeds, nuts, green leafy vegetables and other components of the Mediterranean diet could play a key role in keeping people free from chronic disease.
The Mediterranean diet is popular because it provides the pleasures of pasta, wine and olive oil under the mantle of healthful eating. Several studies suggest that the diet of people who lived in Mediterranean countries during the 1960s contributed to rates of heart disease, cancer and diabetes that were lower than those of people in northern Europe and America.
Thus the traditional Mediterranean diet has been loosely defined as what those people ate: large amounts of cereals (pasta and bread), rice, beans, vegetables, fruits and nuts; smaller amounts of fish, poultry, eggs and dairy products; and still smaller amounts of red meat.
These base foods often were prepared and combined with olive oil and accompanied by wine in moderate amounts. Because those people were very active, daily physical exercise commonly is included as a component of the diet.
Investigators have attributed the health benefits of the diet to multiple factors, which subsequent research has helped confirm: the lack of saturated fat, the vitamins, minerals and phytochemicals in vegetables and fruits; dietary fiber; the cholesterol-lowering compounds in the wine; and the large amount of monounsaturated fat in olive oil.
Now comes another component of this diet: vitamin E.
In March a study published in the British medical journal Lancet showed that vitamin E supplements greatly reduced the number of heart attacks in patients with severe heart disease.
Researchers from Cambridge University fed daily supplements of 400 milligrams or 800 milligrams of vitamin E to 1,000 heart patients, while an equal number were given a placebo. After 17 months, those getting either of the supplements had only a quarter of the number of heart attacks suffered by patients getting a placebo. In fact, they had no more risk of heart attack than people without disease.
The study is the first clinical trial in humans to demonstrate actual benefits from vitamin E, though it confirms several previous observational studies.
Scientists believe that the initial narrowing of the arteries, which can lead to heart attacks and stroke, is caused by the oxidation of low-density lipoproteins–the so-called “bad” cholesterol–which then can lodge in the walls of the blood vessels. Because vitamin E is a powerful, fat-soluble antioxidant, it may prevent this from happening, some researchers theorize.
Research on animals, in tissue samples and even with human arterial lesions supports this theory, says Dr. Herbert J. Kayden, professor of medicine at New York University College of Medicine in New York City.
Other research also indicates that the antioxidant qualities of vitamin E could guard against stomach and other cancers.
Yet like the questions that arise about the other preventive aspects of the Mediterranean diet, exactly how this works or whether it works at all has not been demonstrated conclusively, says Kayden, an authority on how the body stores and uses vitamin E.
“There’s no question that vitamin E is an effective antioxidant in a test tube,” he says, “but it’s difficult to say with absolute security what happens in humans.”
So complicated are the mechanisms involved in atherosclerosis that a definitive study to prove vitamin E’s preventive role could involve thousands of participants and take as long as 40 years, he says.
Kayden can say with certainty that 100 milligrams is the maximum daily amount of vitamin E the human body can use. And that dose, about seven times the recommended daily allowance, has never shown any harmful effects. Dosages of 400 and 800 milligrams are excessive, he says, but they probably aren’t dangerous.
To make things more complicated: It may be difficult to get enough of the right kind of vitamin E from foods, Kayden says. People following the Mediterranean diet probably get more than others, but “you could be eating a lot of soybeans, olive oil and sunflower seeds” to attain 100 milligrams of E.
One problem is that vitamin E exists in several forms, but the only one effective in humans is RRR alpha tocopherol, he says. Not all foods have this form, but it is available in some supplements. Look for the words “vitamin E, alpha tocopherol, made from natural sources” or similar phrasing.
(Just to complicate this even more, some new research at the University of California at Berkeley is indicating that another form of vitamin E–gamma tocopherol found in many vegetables–might also work as an antioxidant, in a different way and independent of the alpha tocopherol, says Bruce Ames, professor and chairman of the department of biochemistry and molecular biology at that school.)
Should you take a supplement just to be sure? And how much should you take?
Kayden says 100 milligrams of natural-source vitamin E per day would be practical.
That’s what he takes.
Steven Pratt’s e-mail address is SMPratt@aol.com
WHERE TO FIND VITAMIN E
Vitamin E is a fat-soluble antioxidant in nuts, grains and seeds and their oils. Some typical oils and their percentage of the Recommended Daily Allowance per tablespoon, unless otherwise noted: %%
Hazelnut oil 64
Sunflower oil 61
Almond oil 53
Cottonseed oil 48
Safflower oil 46
Grapeseed oil 39
Wheat germ (1 ounce) 39
Corn oil 19
Olive oil 16
Peanut oil 16
Soybean oil 15
Stick margarine 12
Mango (3 1/2 ounces) 12
Black currants (1 cup) 11
Blackberries (1 cup) 11
Apple (5 ounces) 8
Source: Prevention Magazine’s Nutrition Advisor %%
