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In recent years, some research has suggested that a high-fat diet may be bad for the brain, at least in lab animals. Can exercise protect against such damage? That question may have particular relevance now, with the butter-and cream-laden holidays fast approaching. And it has prompted several new and important studies.
近年來，一些研究表明高脂飲食可能對大腦有害，至少動物實驗的情況如此。那么，運動能否幫助我們抵抗這種損害呢？隨著節日到來，一大波充斥著黃油和奶酪的食品正在襲來，這個問題有了特殊的重要性，由此也帶來了一些新的重要實驗。
The most captivating of these, presented last month at the annual meeting of the Society for Neuroscience in New Orleans, began with scientists at the University of Minnesota teaching a group of rats to scamper from one chamber to another when they heard a musical tone, an accepted measure of the animals' ability to learn and remember.For the next four months, half of the rats ate normal chow. The others happily consumed a much greasier diet, consisting of at least 40 percent fat. Total calories were the same in both diets.After four months, the animals repeated the memory test. Those on a normal diet performed about the same as they had before; their cognitive ability was the same. The high-fat eaters, though, did much worse.Then, half of the animals in each group were given access to running wheels. Their diets didn't change. So, some of the rats on the high-fat diet were now exercising. Some were not. Ditto for the animals eating the normal diet.
上個月，在新奧爾良神經科學學會(Society for Neuroscience in New Orleans)年會上，明尼蘇達州大學(University of Minnesota)的科學家們提交了一個最為吸引人的發現：他們令一組大鼠聽到音樂后從一個小室疾走到另一個小室，這是一個被普遍認可的測量動物學習和記憶能力的實驗。接下來四個月，一半的老鼠正常飲食，另一半則愉快地享用更為油膩的飲食，其中包含至少40%的脂肪。兩種飲食的總卡路里量是一樣的。四個月后，動物們再次接受記憶測試。正常飲食的大鼠表現與之前一樣；認知能力也一樣。而高脂飲食組的表現就差得多了。接下來，兩組各有一半大鼠被提供了滾輪裝置。它們的飲食沒有變化。這樣，高脂飲食組的一半大鼠開始運動，另一半則沒有運動。正常飲食組的大鼠也是同樣的情況。
For the next seven weeks, the memory test was repeated weekly in all of the groups. During that time, the performance of the rats eating a high-fat diet continued to decline so long as they didn't exercise.But those animals that were running, even if they were eating lots of fat, showed notable improvements in their ability to think and remember.After seven weeks, the animals on the high-fat diet that exercised were scoring as well on the memory test as they had at the start of the experiment.Exercise, in other words, had "reversed the high-fat diet-induced cognitive decline," the study's authors concluded.That finding echoes those of another study presented last month at the Society for Neuroscience meeting. In it, researchers at Kyoto University in Japan gathered a group of mice bred to have a predisposition to developing a rodent version of Alzheimer's disease and its profound memory loss.
接下來的七周中，所有組別每周進行一次記憶測試。在這一階段中，高脂飲食組的大鼠如果沒有運動，表現繼續下降。但是，那些在滾輪上跑步的大鼠雖然也攝入了大量脂肪，但思考和記憶能力有了明顯的提升。七周后，高脂飲食的運動大鼠在記憶測試方面的評分已經恢復到了試驗開始時的水平。研究作者得出了結論：運動“逆轉高脂飲食帶來的認知下降”。這一發現與另一項神經科學學會會議發表的研究互相呼應。在那項研究中，日本京都大學(Kyoto University)的研究人員喂食一組小鼠，使之易于患上嚙齒動物的阿爾茨海默癥和嚴重的記憶喪失。
Just why high-fat diets might affect the brain and how exercise undoes the damage is not yet clear. "Our research suggests that free fatty acids" from high-fat foods may actually infiltrate the brain, says Vijayakumar Mavanji, a research scientist at the Minnesota VA Medical Center at the University of Minnesota, who, with his colleagues Catherine M. Kotz, Dr. Charles J. Billington, and Dr. Chuan Feng Wang, conducted the rat study. The fatty acids may then jump-start a process that leads to cellular damage in portions of the brain that control memory and learning, he says.Exercise, on the other hand, seems to stimulate the production of specific biochemical substances in the brain that fight that process, he says.
為什么高脂飲食損傷大腦而運動又能防御這種損傷，原因還不清楚。美國明尼蘇達大學附屬明尼蘇達VA醫療中心的研究員維查那格·馬凡納(Vijayakumar Mavanji)說，“我們的研究表明游離脂肪酸”是高脂飲食中實際滲透到大腦中的物質，脂肪酸可能啟動反應，造成大腦記憶和學習區域的細胞損傷。他與同事凱瑟琳·M·科茨(Catherine M. Kotz)博士、查爾斯·J·比林頓(Charles J. Billington)博士和王傳峰（Chuan Feng Wang，音譯）博士進行了這項大鼠試驗。馬凡納說，從另一方面來說，運動似乎能刺激大腦中特定生化物質的產生，對抗這一過程。
Of course, lab animals are not people, Dr. Mavanji cautions, and it's not known if exercise might protect our brains in the same manner as it does in mice and rats.Still, he says, there's enough accumulating evidence about the potential cognitive risks of high-fat foods and the countervailing benefits from physical activity to recommend that "people exercise moderately," he says, particularly during periods of repeated exposure to alluring, fatty holiday buffets.
當然，試驗動物與人類不同。馬凡納博士提醒說，現在尚不清楚運動是否能像保護小鼠和大鼠一樣保護我們的大腦。但他說，目前已經積累了足夠證據，說明高脂飲食能帶來潛在的認知風險，而鍛煉運動能產生與之相抗衡的益處，因此他建議“人們適度運動”，在假期面對誘人的肥膩的自助餐時尤其需要如此。
