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19、 Eating potatoes gives your immune system a boost Eating potatoes is not only good for bowel health, but also for the whole immune system, especially when they come in the form of a potato salad or eaten cold. In a study on an animal model, researchers in Spain found that pigs fed large quantities of raw potato starch (RPS)1 not only had a healthier bowel, but also decreased levels of white blood cells, such as leucocytes and lymphocytes in their blood. White blood cells are produced as a result of inflammation or disease, generally when the body is challenged. The general down-regulation of leucocytes observed by the Spanish researchers suggests an overall beneficial effect, a generally more healthy body.2 The reduction in leucocyte levels was about 15 percent. Lower lymphocyte levels are also indicative of reduced levels of inflammation, but the observed reduction in both lymphocyte density and lymphocyte apoptosis is surprising. In what was the longest study of its kind, pigs were fed RPS over 14 weeks to find out the effect of starch on bowel health. “The use of raw potato starch in this experiment is designed to simulate the effects of a diet high in resistant starch”, said study leader Jose Francisco Perez at the Universitat Autonoma de Barcelona,3 Spain. Humans do not eat raw potatoes, but they do eat a lot of foods that contain resistant starch, such as cold boiled potatoes, legumes, grains, green bananas, pasta and cereals. About 10 percent of the starch eaten by human is resistant starch - starch that is not digested in the small intestine and so is shunted into the large intestine where it ferments. Starch consumption is thought to reduce the risk of large bowel cancer and may also have an effect on irritable bowel syndrome (IBS). Immunology expert Lena Ohman’s team previously found that the overall lymphocyte levels do not vary for IBS patients, but that lymphocytes are transferred from the peripheral blood to the gut, which support the hypothesis of IBS being at least partially an inflammatory disorder. She says the decrease in lymphocytes observed by the Spanish is therefore interesting, and a diet of resistant starch may be worth trying in IBS patients. Ohman is currently at the Department of Internal Medicine, Goteborg University, Sweden.5 The study is published in the journal Chemistry and Industry, the magazine of the SCI.6
1What a form of potato is the most nutrient to the human body? .
2 What does the reduction in leucocyte levels in the body mean?
3For what a purpose did the researchers use raw potato starch in their experiment?
4 All of the following foods are rich in resistant starch EXCEPT __________.
5What a kind of starch is resistant starch after all?
20、 Find Yourself Packing It On? Blame Friends Obesity can spread from person to person, much like a virus, researchers are reporting today. When one person gains weight, close friends tend to gain weight, too. Their study, published in The New England Journal of Medicine, involved a detailed analysis of a large social network of 12,067 people who had been closely followed for 32 years, from 1971 to 2003. The investigators knew who was friends with whom as well as who was a spouse or sibling or neighbor, and they knew how much each person weighed at various times over three decades. That let them reconstruct what happened over the years as individuals became obese. Did their friends also become obese? Did family members? Or neighbors? The answer, the researchers report, was that people were most likely to become obese when a friend became obese. That increased a persons chances or becoming obese by 57 percent. There was no effect when a neighbor gained or lost weight，however, and family members had less influence than friends. It did not even matter if the friend was hundreds of miles away, the influence remained. And the greatest influence of all was between close mutual friends. There, if one became obese, the other had a 171 percent increased chance of becoming obese, too. The same effect seemed to occur for weight loss, the investigators say. But since most people were gaining, not losing, over the 32 years, the result was, on average, that people grew fatter. Dr. Nicholas A. Christakis, a physician and professor of medical sociology at Harvard Medical School and a principal investigator in the new study, said one explanation was that friends affected each others’ perception of fatness. When a close friend becomes obese, obesity may not look so bad. “You change your idea of what is an acceptable body type by looking at the people around you,” Dr. Christakis said. The investigators say their findings can help explain why Americans have become fatter in recent years – each person who became obese was likely to drag along some friends! Their analysis was unique, Dr. Christakis said, because it moved beyond a simple analysis of one person and his or her social contacts and instead examined an entire social network at once, looking at how a person''s f
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