Ratsthateathighlevelsofanaturalsugarknownasfructose（...

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Rats that eat high levels of a natural sugar known as fructose（果糖）seem to age faster than other rats-and the same could be true for people who eat too much sweet junk food, Israeli researchers said Monday．

Fructose, found naturally in honey and fruit, is used widely in foods ranging from soft drinks to yogurt．But while its sweet taste is popular, the sugar could cause wrinkles, the researchers said．Dr．Moshe Werman and Boaz Levi of the Technion-Israel Institute of Technology fed large amounts of fructose to laboratory rats．Writing in the Journal of Nutrition, they said the fructose-fed rats showed changes in the collagen （胶原蛋白）of their skin and bones．Collagen basically holds the body together．The loss of collagen is what causes loose skin and deep wrinkles in older people,

The process affected, Werman's team said, is known as cross-linking（交叉相连） "．"Too much cross-linking makes the skin stiff, and these are the conditions that encourage wrinkled skin," Werman said in a statement．He said the same could be true of people, although this has not been shown．"Americans are eating more and more processed foods such as baked goods, canned fruits, jams and dairy products that contain fructose," Werman said．Other studies have shown that taking in high fructose may cause diabetes（糖尿病）．

The rats Werman worked with were fed much more than the average adult person might eat in a day, which is standard in such experiments．The rats were fed 12.5 grams of fructose per kg of weight every day for a year．

32．In 'the experiments, if a rat was 0．25 kg, it may have been fed about grams of fructose every day for a year．

A．3 B．4 C． 5 D．6

33．Why do older people have deep wrinkles according to the passage?

A．They don't drink enough water every day．'

B．They don't take enough exercise every day．

C．Collagen in their body is lost,

D．Their daily foods do not contain enough fructose．

34．What can we learn from the passage?

A．The fructose-fed rats only showed changes in the collagen of their skin．

B．Too much cross-linking makes the skin soft．

C．The amount of sugar the rats ate was larger than an ordinary adult might eat in a day．

D．It hasn't been shown that taking in high fructose may cause diabetes．