Vitamin E's Dark Side

　　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. However, 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.

　　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.

　　科学家曾在实验中发现维他命E可以在某种条件下增强人体内部的氧化作用，这种催化作用对食用大量不饱和脂肪的吸烟者特别明显，一项新的研究证实了这一点。

　　人体内的氧化作用会产生损坏身体组织的有害微粒。抗氧化物，如维生素E等，一向被认为通过能减低氧化作用，来治疗某些疾病。但美国北卡罗莱纳州维克-佛里斯大学的温博格教授及其同事却在6月号的美国心脏医学会《动脉硬化、血栓形成和血管生物学》期刊上撰文指出，一些数据显示，实际上维生素E会增加吸烟者心脏病突发和中风的风险。

　　温博格小组的研究对象是10名每天吸烟超过一包的烟民。实验的前3周，研究人员给他们安排单饱和脂肪的食谱，后3周里则安排多饱和脂肪的食谱。研究对象在实验过程中，体内指示氧化作用发生的前列腺素F2-α水平不断上升。于是研究人员在后3周的食谱中每天加入了800单位的维生素E，3周后，实验对象体内的氧化作用反而更多。

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