大剂量的维生素E可以保护动脉血管
【摘要】发表在美国第41届心血管疾病流行和预防年会上的一项研究报告指出：服用大剂量维生素E可以防止动脉硬化，从而达到防止心血管疾病发生的作用。【全文】High-dose vitamin E may protect arteriesSAN ANTONIO, Mar 05 (Reuters Health) - Taking high doses of vitamin E may help prevent heart attacks and strokes by preventing the progression of hardening of the arteries, according to study findings presented here at the 41st Annual Conference on Cardiovascular Disease Epidemiology and Prevention.Dr. James H. Dwyer of Keck School of Medicine, University of Southern California, said the effect is limited to doses of more than 300 milligrams a day. These high doses--sometimes as high as 1,000 milligrams a day--were associated with a slower progression of atherosclerosis, the disease commonly called hardening of the arteries. The recommended dietary allowance for vitamin E is 15 milligrams per day for adult men and women, and the tolerable upper intake level (UL) is 1,000 milligrams per day. People who take more than the UL may increase their risk of hemorrhage, according to the Institute of Medicine. Anyone considering taking higher-than-recommended doses of the vitamin should consult their doctor first.Dwyer checked the effect of vitamin E by measuring the build-up of plaque in the carotid arteries of 573 men and women who work for a California utility company. The carotid arteries are located in the neck, and clogging of the arteries can increase the risk of stroke.At annual check-ups, Dwyer used ultrasound to measure the thickness of the arterial walls in the volunteers who were healthy and free of diagnosed cardiovascular disease when the study began in 1994.In addition to measuring the carotid arteries, Dwyer and his colleagues used questionnaires to gather information about the use of vitamin supplements and diet. This latest report is based on 3 years' of ultrasound screenings.In an interview with Reuters Health, Dwyer said the study volunteers were divided into four groups based on the use of vitamin E. The benefit was only seen in the group taking the highest level of the vitamin. He added that the benefit was limited to "vitamin E from supplements. We found no effect for dietary vitamin E."While vitamin E was beneficial, vitamin C--another antioxidant--had no benefit and appeared to promote the progression of disease. Dwyer initially reported this negative finding for vitamin C last year based on 2 years' ultrasound data."Dwyer said he could not explain why one antioxidant was beneficial while the other was harmful, but said that in laboratory experiments biochemists have demonstrated that high levels of vitamin C "could induce a pro-oxidant pathway."That would mean that vitamin C was promoting oxidation of LDL ("bad") cholesterol. This oxidation process contributes to the build-up of plaque, the substance that narrows arteries. He said, however, that this effect has only been demonstrated in test tubes, not humans., http://www.100md.com
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