WASHINGTON - People loading up on vitamin E supplements to stay healthy may be making a mistake. Researchers say most pills have only one form of the nutrient and it can be harmful in large doses.
People should take only modest levels of vitamin E in pills and then eat foods that contain more complete forms of the nutrient, said Stephan Christen, a biochemist and researcher at the University of California, Berkeley.
Earlier studies had shown that vitamin E protects against heart disease and cancer and slows aging by absorbing oxygen free radicals, destructive chemicals that form during metabolism and when the body fights disease.
But a study to be published Tuesday in the Proceedings of the National Academy of Sciences suggests that alpha-tocopherol, the form of vitamin E found in pills, does an incomplete job of neutralizing some compounds.
To get full benefit from the vitamin, people also need gamma-tocopherol, found in soybeans, nuts and grains, said Christen, lead author of the study.
The researcher said he hopes vitamin pill companies soon will add that second form of the vitamin to their formulas. It is the main form of vitamin E in the American diet, said Christen, "but it stays in the body only a short time."
Christen said that of the E vitamins, only gamma-tocopherol gets rid of peroxynitrite, a highly destructive nitric oxide radical found at sites of inflammation. Where there is chronic inflammation, he said, peroxynitrite can start processes leading to cancer and heart disease.
In laboratory tests, Christen said, California researchers found that gamma-tocopherol also was the only one of the E vitamin forms that could permanently trap and remove nitrogen oxide, a chemical commonly found in polluted air.
Additionally, the studies showed that high levels of alpha-tocopherol reduce the levels of gamma-tocopherol in the blood. Thus, said Christen, high doses of current vitamin E pills actually can block a beneficial natural nutrient.
"The initial evidence is pretty clear," he said. "We should not be taking only alpha-tocopherol in supplements."
Since few pills now contain both the alpha and gamma forms of vitamin E, Christen said people should limit the amount of the supplement they take. Amounts above 100 international units may be harmful, he said.
John Hathcock, of the Council for Responsible Nutrition, a trade association for vitamin pill makers, disagreed. He said high doses of vitamin E have been found to lower the "bad" type of cholesterol in the blood.
Hathcock said Christen's study was "an important expansion" in understanding gamma-tocopherol, "but what is lacking is any proof that this makes any clinical difference."
He said a healthy diet of fruits and vegetables has nutrients that will neutralize destructive chemicals missed by vitamin E in supplements.
Christen said he recommends that vitamin pill companies make a vitamin E supplement that is half-and-half, alpha and gamma tocopherol.
"There is no reason not to do this since supplements with a mixture of alpha and gamma would be cheap to make," he said. "Both are readily extracted from plants such as soybeans."