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Vitamins Found to Curb Exercise Benefits

Vitamins Found to Curb Exercise Benefits

Vitamins Found to Curb Exercise Benefits

原文链接:http://www.nytimes.com/2009/05/12/health/research/12exer.html

By NICHOLAS WADE
Published: May 11, 2009
If you exercise to improve your metabolism and prevent diabetes, you may want to avoid antioxidants like vitamins C and E.

That is the message of a surprising new look at the body’s reaction to exercise, reported on Monday by researchers in Germany and Boston.

Exercise is known to have many beneficial effects on health, including on the body’s sensitivity to insulin. “Get more exercise” is often among the first recommendations given by doctors to people at risk of diabetes.

But exercise makes the muscle cells metabolize glucose, by combining its carbon atoms with oxygen and extracting the energy that is released. In the process, some highly reactive oxygen molecules escape and make chemical attacks on anything in sight.

These reactive oxygen compounds are known to damage the body’s tissues. The amount of oxidative damage increases with age, and according to one theory of aging it is a major cause of the body’s decline.

The body has its own defense system for combating oxidative damage, but it does not always do enough. So antioxidants, which mop up the reactive oxygen compounds, may seem like a logical solution.

The researchers, led by Dr. Michael Ristow, a nutritionist at the University of Jena in Germany, tested this proposition by having young men exercise, giving half of them moderate doses of vitamins C and E and measuring sensitivity to insulin as well as indicators of the body’s natural defenses to oxidative damage.

The Jena team found that in the group taking the vitamins there was no improvement in insulin sensitivity and almost no activation of the body’s natural defense mechanism against oxidative damage.

The reason, they suggest, is that the reactive oxygen compounds, inevitable byproducts of exercise, are a natural trigger for both of these responses. The vitamins, by efficiently destroying the reactive oxygen, short-circuit the body’s natural response to exercise.

“If you exercise to promote health, you shouldn’t take large amounts of antioxidants,” Dr. Ristow said. A second message of the study, he said, “is that antioxidants in general cause certain effects that inhibit otherwise positive effects of exercise, dieting and other interventions.” The findings appear in this week’s issue of The Proceedings of the National Academy of Sciences.

The effect of vitamins on exercise and glucose metabolism “is really quite significant,” said Dr. C. Ronald Kahn of the Joslin Diabetes Center in Boston, a co-author of the report. “If people are trying to exercise, this is blocking the effects of insulin on the metabolic response.”

The advice does not apply to fruits and vegetables, Dr. Ristow said; even though they are high in antioxidants, the many other substances they contain presumably outweigh any negative effect.

Dr. Kahn said it might be that reactive oxygen is beneficial in small doses, because it touches off the body’s natural defense system, but harmful in higher doses.

Andrew Shao of the Council for Responsible Nutrition, a trade association of dietary supplement makers, said the new study was well designed but was just one bit of evidence in a complex issue. Most available evidence points to the opposite conclusion, that antioxidants benefit health by reducing oxidative stress, he said.

“I wouldn’t change recommendations for anyone based on one study,” he said. “This is one small piece of the puzzle.”


维生素限制了运动的效果

发布时间: 2009年5月11号
如果您运动的目的是改善您的新陈代谢和预防糖尿病的话,应该尽可能的避免服用像抗氧化剂的物质如维生素C和E

周一研究人员在德国和波士顿发表报告称,这是一个令人惊讶的消息。 运动对人类的健康有许多益处,包括提高人体对胰岛素的敏感性。 对于具有高糖尿病患病风险的人来说,医生们最先考虑的建议就是多多参加运动。
但是,运动使得肌肉细胞代谢葡萄糖,其碳原子与氧结合和能量释放。在这个过程中,一些高活性氧分子逃跑,使化学攻击没有留下任何迹象。
这些活性氧化合物是众所周知的损害身体组织。氧化损伤的程度随着年龄的增长而变的越来越严重;根据这一理论,其是人体衰老而引起体质下降的主要原因之一。
人体拥有自己的防御氧化损伤的系统,但并不总是做完美。因此,用抗氧化剂吸纳活性氧化合物,可能看起来是一种非常合乎逻辑的解决办法。
德国耶拿大学的研究人员迈克尔Ristow博士是一位营养学家,通过让年轻人参加锻炼,并让其中一半的人服用中等程度的维生素C和E;测量他们对胰岛素的敏感性及天然防御氧化损伤的指标。 研究发现:服用维生素的人,其对胰岛素的敏感性没有任何改变;几乎没有激活任何的天然防御机制对氧化损伤。 他们认为其原因是活性氧化合物(运动不可避免产生的分解产物)是一种自然的反应。维生素,有效地破坏了活性氧,从而使身体对运动产生的自然的反应时间变短。
博士Ristow说“如果你运动的目的是促进健康的话,就不应该摄入大量的抗氧化剂”。 他说,此项研究的第二个消息是:一般情况下,抗氧化剂对积极的体育锻炼造成一定的影响。
维生素对运动及糖代谢的影响是非常重要的。如果人们正在积极的运动的话,就阻碍了胰岛素在新陈代谢中的反应。
不过此项建议并不适用于水果和蔬菜,因为水果蔬菜所含有的抗氧化剂可能带来的负面影响,已经远远超过了水果蔬菜所带来的积极的影响。
卡恩说,可能小剂量的活性氧是有利的,因为它涉及了身体的天然防御系统,但较高剂量则是有害的。
新研究是精心设计的,但仅仅是一个复杂的问题的其中的一点证据而已。大多数现有的证据指向相反的结论,即抗氧化剂减少氧化应激对健康的有害的影响。基础这项研究,不会改变任何人的建议。


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