Vitamin May Speed Oxidation

WESTPORT, Conn. (Reuters Health) - A new study confirms laboratory findings that suggest vitamin E can promote oxidation in the human body under certain conditions--specifically, in smokers eating a diet high in polyunsaturated fat.

Oxidation is a chemical reaction in the body that can produce harmful molecules that damage tissue. Antioxidants--such as vitamin E--are believed to help fight certain illnesses by blunting the effects of oxidation.

In some past studies, vitamin E has not been protective against heart or blood vessel disease caused by atherosclerosis, or hardening of the arteries. Some data suggest that it actually increases the risk of heart attack and stroke in smokers, Dr. Richard B. Weinberg of Wake Forest University, Winston-Salem, North Carolina, and colleagues note in the June issue of Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association.

To see if vitamin E can function as a pro-oxidant, meaning it promotes oxidation rather than fighting it, Weinberg's team assigned 10 people who smoked more than one pack of cigarettes per day to follow a diet high in monounsaturated fat for 3 weeks, then a diet high in polyunsaturated fat for 3 weeks.

People in the study had increased levels of F2-isoprostanes and prostaglandin F2-alpha, chemicals that indicated oxidation was taking place.

Then the researchers added 800 IU vitamin E per day to the polyunsaturated fat diet. After 3 weeks, ``we found that there was even more oxidation,'' Weinberg told Reuters Health. Mean levels of F2-isoprostanes and prostaglandin F2-alpha increased further.

``Even though it is unlikely that many smokers would consume a diet containing the high content of polyunsaturated fatty acid that we used...because F2-isoprostanes are vasoactive act on the blood vessels and increase platelet activation, our findings suggest caution in the use of high-dose vitamin E supplementation as a therapeutic means to reduce the risk of atherosclerotic cardiovascular disease in cigarette smokers,'' the researchers conclude.

``These results add some biological reality to the debate about antioxidants, and indicate that antioxidants are not in all circumstances uniformly good and harmless,'' Weinberg said.

He added that ``if vitamin E can become a pro-oxidant in the human body, this may be one of the reasons why studies have shown that vitamin E does not seem to have the great protective effect that we think it should have.''

SOURCE: Arteriosclerosis, Thrombosis and Vascular Biology 2001;21:1029-

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