Eat to Live

A meager diet may give you health and long life,but it's not much fun-and it might not even be necessary.We may be able to hang on to most of that youthful vigor even if we don't start to diet until old age.

Stephen Spindler and his colleagues from the University of California at Riverside have found that some of an elderly mouse's liver genes can be made to behave as they did when the mouse was young simply by limiting its food for four weeks.The genetic rejuvenation won't reverse other damage caused by time for the mouse,but could help its liver metabolize drugs or get rid of toxins.

Spindler's team fed three mice a normal diet for their whole lives,and fed another three on half-rations.Three more mice were switched from the normal diet to half-feed for a month when they were 34 months old - equivalent to about 70 human years.

The researchers checked the activity of 11,000 genes from the mouse livers,and found that 46 changed with age in the normally fed mice.The changes were associated with things like inflammation and free radical production - probably bad news for mouse health.In the mice that had dieted all their lives,27 of those 46 genes continued to behave like young genes.But the most surprising finding was that the mice that only started dieting in old age also benefited from 70 percent of these gene changes.

"This is the first indication that the effects kick in pretty quickly,"says Huber Warner from the National Institute on Aging near Washington,D.C.

No one yet knows if calorie works in people as it does in mice,bus Spindler is hopeful."There's attracting and tempting evidence out there that it will work,"he says.

If it does work in people,there might be good reasons for rejuvenating the liver.As we get older,out bodies are less efficient at metabolizing drugs,for example.A brief period of time of dieting,says Spindler,could be enough to make sure a drug is effective.

But Spindler isn't sure the trade-off is worth it."The mice get less disease,they live longer but they're hungry,"he says."Even seeing what a diet does,it's still hard to go to a restaurant and say:'I can only eat half of that'."

Spindler hopes we soon won't need to diet at all.His company,Life Span Genetics in California,is looking for drugs that have the effects of calorie restriction.

1.According to the passage,which of the following is NOT true?

A)Eating less than usual might make us live longer.

B)If we go on a diet when old,we may keep healthy.

C)Dieting might not be needed.

D)We have to begin dieting from childhood.

2.Why does the author mention an elderly mouse in paragraph 2？

A)To describe the influence of old age on mice.

B)To illustrate the effect of meager food on mice.

C)To tell us how mice's liver genes behave.

D)To inform us of the process of metabolizing drugs.

3.What can be inferred about completely normally fed mice mentioned in the passage？

A)They will not experience free radical production.

B)They will experience more genetic rejuvenation in their lifetime.

C)They have more old liver genes to behave like young genes.

D)They are more likely to suffer from inflammation.

4.According to the author,which of the following most interested the researchers？

A)The mice that started dieting in old age.

B)27 of those 46 old genes that continued to behave like young genes.

C)Calorie restriction that works in people.

D)Dieting that makes sure a drug is effective.

5.According to the last two paragraphs,Spindler believes that ______.

A)calorie restriction is very important to young people.

B)seeing the effect of a diet,people will like to eat less than normal.

C)dieting is not a good method to give us health and a long life.

D)drugs do not have the effects of calorie restriction.

參考答案：1.D 2.B 3.D 4.A 5.C

為生存而食

粗茶淡飯或許能給你健康長壽,但這并不有趣——很可能也沒必要。即便在老年以后才開始節(jié)食我們也能在很大程度上保持青春活力。

加州大學(xué)Riverside分校的斯蒂芬？斯潘德爾及其同事發(fā)現(xiàn),只要連續(xù)四周限制一些衰老的老鼠進食,它的肝臟基因就會變得和衰老前一樣充滿活力。雖然老鼠的肝部基因恢復(fù)活力不會逆轉(zhuǎn)老鼠在其他方面的老化,但卻有助于這些老鼠的肝臟對藥物的新陳代謝和清除毒素。

斯潘德爾的隊員們一直給其中的三只老鼠正常量的飼料,而給另外三只老鼠正常量飼料的一半,給三只34個月大的老鼠（相當(dāng)于人類年齡的70歲）喂了一個月的半量飼料,之前這三只老鼠的飼料量是正常的。

研究者檢查了這些老鼠肝臟的11000個基因的活性,發(fā)現(xiàn)正常飼養(yǎng)的老鼠有46種基因隨年齡的改變而改變。這些改變都與機體組織的無限激增有關(guān)——這對老鼠的健康來說并不是什么好消息。而對于那些終身都在節(jié)食的老鼠來說,那46種基因中的27種仍然繼續(xù)保持著青春活力。但是最令人吃驚的發(fā)現(xiàn)卻是那些只是在老年時期節(jié)食的老鼠們受益于70%的基因變異。

"這只是第一個這些效果迅速起作用的暗示”,來自華盛頓特區(qū)周邊的國家老年學(xué)學(xué)院的哈勃？華納說。

至今仍然沒有人清楚卡路里的控制對人類來說是否如同對老鼠那樣有效,但是斯潘德爾對此充滿了希望："有足以引人注意的證據(jù)表明這同樣有效。”

如果這確實也對人類有效,我們有理由相信肝臟也可能恢復(fù)活力。舉個例子,隨著我們一天天衰老,我們的身體對藥物的新陳代謝越來越?jīng)]有效率。短時期內(nèi)的節(jié)食,斯潘德爾說到,完全足以保證藥效。

但是斯潘德爾并不確定這個方法值得嘗試。"老鼠患病少了,壽命延長了,但是他們很饑餓,”他說,"即使能清楚地認識到節(jié)食的功效,人們?nèi)匀缓茈y在餐館中說自己只能吃一半的食物。”

斯潘德爾希望我們根本就不用節(jié)食。他的公司,加利福尼亞州的壽命遺傳學(xué)公司,正在尋找有限制卡路里效能的藥物。

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