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美科学家称低卡路里饮食未必长寿

更新时间:2020-1-31 9:54:49 来源:本站原创 作者:佚名 浏览:

Severe Diet Doesn’t Prolong Life, at Least in Monkeys
美科学家称低卡路里饮食未必长寿

For 25 years, the rhesus monkeys from China and India were kept semi-starved, lean and hungry. The males’ weights were so low they were the equivalent of a 6-foot-tall man who tipped the scales at just 120 to 133 pounds. The hope was that if the monkeys lived longer, healthier lives by eating a lot less, then maybe people, their evolutionary cousins, would, too. Some scientists, anticipating such benefits, began severely restricting their own diets.

过去25年当中,来自中国和印度的一些猕猴始终被保持在半饥饿状态,身体精瘦、饥肠辘辘。公猴的体重很轻,瘦的程度相当于一个身高1.8米左右,体重却只有120到133磅的男人。科学家们的希望是,如果猴子可以通过少吃达到健康长寿的目的的话, 它们在进化意义上的近亲人类,或许也可以如此。从这些益处着眼,一些科学家已经开始严格限制自己的饮食。

The results of this major, long-awaited study, which began in 1987, are finally in. But it did not bring the vindication calorie restriction enthusiasts had anticipated. It turns out the skinny monkeys did not live any longer than those kept at more normal weights. Some lab test results improved, but only in monkeys put on the diet when they were old. The causes of death — cancer, heart disease — were the same in both the underfed and the normally fed monkeys.

这项令人期待已久的重大研究始于1987年,如今终于公布了结果。但研究却并没有证实那些热衷节减卡路里的人们预期的益处。结果显示,瘦得皮包骨头的猴子并不比那些正常体重的同类活得长。一些实验室测试结果有所改善,但仅限于那些步入老年之后才开始节食的猴子。不管节食与否,猴子的死亡原因——癌症、心脏病——都是一样的。

Lab test results showed lower levels of cholesterol and blood sugar in the male monkeys that started eating 30 percent fewer calories in old age, but not in the females. Males and females that were put on the diet when they were old had lower levels of triglycerides, which are linked to heart disease risk. Monkeys put on the diet when they were young or middle-aged did not get the same benefits, though they had less cancer. But the bottom line was that the monkeys that ate less did not live any longer than those that ate normally.

实验结果显示,老年公猴的饮食所含卡路里减少30%之后,它们的胆固醇和血糖水平有所降低,但是母猴的情况没有变化。节食的老年公猴和母猴都拥有较低的三酸甘油酯水平,三酸甘油酯是一种诱发心脏病的物质。节食的幼年或者中年猴子并没有获得这些益处,得癌症的几率却有所减少。不过,再怎么说 ,吃得少的猴子并不比饮食正常的猴子寿命更长。

Rafael de Cabo, lead author of the diet study, published online on Wednesday in the journal Nature, said he was surprised and disappointed that the underfed monkeys did not live longer. Like many other researchers on aging, he had expected an outcome similar to that of a 2009 study from the University of Wisconsin that concluded that caloric restriction did extend monkeys’ life spans.

这篇节食论文于周三在《自然》(Nature)杂志发表,论文的首要作者拉斐尔·德·卡博(Rafael de Cabo)称,他觉得既惊讶又失望,因为节食的猴子寿命没有增加。和许多研究老龄化的学者一样,他本来估计能得到一个与2009年威斯康星大学的研究类似的结果,那项研究的结论是,减少卡路里的确可以延长猴子的生命。

But even that study had a question mark hanging over it. Its authors had disregarded about half of the deaths among the monkeys they studied, saying they were not related to aging. If they had included all of the deaths, there was no extension of life span in the Wisconsin study, either.

不过,即使是那项研究也有一个可疑之处。研究报告的各位作者忽略了半数在研究过程中死亡的猴子,称这与老龄化无关。如果威斯康星的研究者把死亡的所有猴子都包括进来的话,那么,他们的研究也不能证明猴子寿命会延长。

“This shows the importance of replication in science,” Steven Austad, interim director of the Barshop Institute for Longevity and Aging Studies at the University of Texas Health Science Center in San Antonio. Dr. Austad, who was not involved with either study, said that the University of Wisconsin study “was not nearly as conclusive as it was made out to be” and that the new study casts further doubt on the belief that caloric restriction extends life.

“这显示了可重复性对于科学的重要性,”史蒂夫·奥斯塔德(Steven Austad)称,他是德克萨斯大学圣安东尼奥健康科学中心巴肖普长寿与老龄化研究院(Barshop Institute for Longevity and Aging Studies at the University of Texas Health Science Center in San Antonio)的临时主任。没有参与这两次研究的奥斯塔德称,威斯康星大学的研究“远不如它自称的那样具有确定性”。他还说,这项新研究也使人们进一步怀疑减少卡路里可以延长寿命的说法。

But other researchers still think that it does, and one of the authors of the new study, Julie A. Mattison, said it was still possible that some benefit would be revealed. The study is continuing until the youngest monkeys are 22 years old. While the data pretty much rule out any notion that the low-calorie diet will increase average life spans, there still is a chance that the study might find that the diet increases the animals’ maximum life span, she said.

然而,另一些研究者依然相信这一说法。新论文的作者之一朱莉·A·马蒂森(Julie A. Mattison)称,将来还是有可能发现一些节食带来的益处。这项研究会继续进行到最年轻的猴子年满22岁的时候。她说,虽然目前的数据在很大程度上排除了低卡路里饮食可以增加平均寿命的说法,但是将来的研究仍然有可能发现,节食可以增加动物的寿限。

Meanwhile, some others said that the Wisconsin study made them reluctant to dismiss the idea that low-calorie diets result in longer life.

与此同时,其他一些人表示,他们之所以不愿意放弃低卡路里饮食会延长寿命的观点,是因为看到了威斯康星大学的研究。

“I wouldn’t discard the whole thing on the basis of one study, when another study in the same species showed an increase in life span,” said Eric Ravussin, director of the nutritional obesity research center at the Pennington Biomedical Research Center in Louisiana. “I would still bet on an extension of life.”

“既然针对相同物种的另一项研究表明会延长寿命,我就不会因为单独的一项研究而摈弃全部,”路易斯安那州彭宁顿生物医学研究中心(Pennington Biomedical Research Center)营养型肥胖研究中心主任埃里克·拉弗森(Eric Ravussin)说。“我还是打赌会延长寿命。”

The idea that a low-calorie diet would extend life originated in the 1930s with a study of laboratory rats. But it was not until the 1980s that the theory took off. Scientists reported that in species as diverse as yeast, flies, worms and mice, eating less meant living longer. And, in mice at least, a low-calorie diet also meant less cancer. It was not known whether the same thing would hold true in humans, and no one expected such a study would ever be done. It would take decades to get an answer, to say nothing of the expense and difficulty of getting people to be randomly assigned to starve themselves or not.

低卡路里饮食会延长寿命的说法最早来自上世纪30年代一项以实验室老鼠为对象的研究。然而,直到80年代,这个理论才突然流行起来。科学家报告称,对于酵母菌、苍蝇、蠕虫、老鼠等千差万别的物种来说,少吃都意味着活得更久。此外,起码在老鼠身上,低卡路里饮食还意味着患癌几率更小。那时还不清楚同样的规律是否适用于人类,也没人觉得会有人去做这样的研究。得到答案要花几十年时间,更不用说,让人们接受随机分配的挨饿或不挨饿待遇需要多大的成本、会面对多大的困难。

Researchers concluded the best way to test the hypothesis would be through the monkey studies at the University of Wisconsin and the National Institute on Aging, although the animals would have to be followed for decades.

研究人员得出结论,检验这个假设的最佳办法是让威斯康星大学和国家老龄化研究所(National Institute on Aging)来进行猴子实验,尽管要对实验动物跟踪几十年。

It was a major endeavor. The National Institute on Aging study involved 121 monkeys, 49 of which are still alive, housed at a facility in Poolesville, Md. Those that got the low-calorie diet did not act famished, Dr. de Cabo said. They did not gobble their food, for example, but ate at the same speed as the control animals, even though their calories had been cut by 30 percent.

这是一次大规模的尝试。国家老龄化研究所的研究涉及121只猴子,其中的49只至今都还活着,被养在马里兰州普尔斯维尔的一处设施里。卡博博士说,那些吃低卡路里食物的猴子没有表现出很饿的样子。比如,尽管它们获得的卡路里被减少了30%,但它们吃东西的时候并没有狼吞虎咽,速度和对照组的动物一样。

As the studies were under way, some human enthusiasts decided to start eating a lot less, too.

随着实验继续进行,人类当中的一些热心者也决定节食了。

In those same years, though, studies in mice began indicating there might not be a predictable response to a low-calorie diet. Mice that came from the wild, instead of being born and raised in the lab, did not live longer on low-calorie diets. And in 2009, a study of 41 inbred strains of laboratory mice found that about a third had no response to the diets. Of those that responded, more strains had shorter life spans than had longer ones when they were given less food.

然而,也是在那些年里,以老鼠为对象的研究表明,低卡路里饮食可能不会导致可以预计的确定结果。来自野外而非在实验室里生养的老鼠,在吃低卡路里食物时并没有活得更久。此外,2009年一项以实验室老鼠的41个近交品种为对象的研究发现,大约三分之的品种对饮食变化没有反应。在那些有反应的品种当中,当吃的食物比较少时,寿命缩短的品种比寿命增加的多。

Dr. de Cabo, who says he is overweight, advised people that if they want to try a reduced-calorie diet, they should consult a doctor first. If they can handle such a diet, he said, he believes they would be healthier, but, he said, he does not know if they would live longer.

自认超重的卡博博士建议说,如果想尝试低卡路里的饮食,人们首先应该咨询一下医生。他说他相信,能适应这种饮食的人会活得更健康,但他也表示,他不知道这样的人会不会活得更久。

Some scientists still have faith in the low-calorie diets. Richard Weindruch, a director of the Wisconsin study, said he was “a hopeless caloric-restriction romantic,” but added that he was not very good at restricting his own calories. He said he might start trying harder, though: “I’m only 62. It isn’t too late.”

一些科学家依然对低卡路里饮食有信心。威斯康辛研究负责人之一理查德·魏因德瑞(Richard Weindruch)说,自己是“一个不可救药的限制卡路里拥趸”,然后又补充说,他不太善于限制自己摄入卡路里。不过,他表示以后可能会对自己狠点儿:“我才62岁。还不算太晚。”

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