Book 1 Reading and Speaking (1108795), страница 26
Текст из файла (страница 26)
Beta-carotene belongs to a group of antioxidant substances calledcarotenoids, which give fruits and vegetables their red, yellow, and orange colorings. The body converts betacarotene into vitamin A, which plays an important role in vision, reproduction, bone growth and regulating theimmune system.The downside of cooking veggies, Liu says: it can destroy the vitamin C in them. He found that vitamin Clevels declined by 10 percent in tomatoes cooked for two minutes—and 29 percent in tomatoes that were cookedfor half an hour at 190.4 degrees F (88 degrees C). The reason is that Vitamin C, which is highly unstable, is easilydegraded through oxidation, exposure to heat (it can increase the rate at which vitamin C reacts with oxygen in theair) and through cooking in water (it dissolves in water). Liu notes, however, that the trade-off may be worth it sincevitamin C is prevalent in far more fruits and vegetables than is lycopene.
Among them: broccoli, oranges,cauliflower, kale and carrots. Besides, cooked vegetables retain some of their vitamin C content.That said, research shows that some veggies, including broccoli, are healthier raw rather than cooked.According to a study in the Journal of Agricultural and Food Chemistry in November 2007, heat damages theenzyme myrosinase, which breaks down glucosinates (compounds derived from glucose and an amino acid) inbroccoli into a compound known as sulforaphane.
Research published in the journal Carcinogenesis in December2008 found that sulforaphane might block the proliferation of and kill precancerous cells. A 2002 study in TheProceedings of the National Academy of Sciences also found that sulforaphane may help fight the bacteriumHelicobacter pylori, which causes ulcers and increases a person's risk of stomach cancer.On the other hand, indole, an organic compound, is formed when certain plants, particularly cruciferousvegetables such as broccoli, cauliflower and cabbage, are cooked. According to research in The Journal ofNutrition in 2001, indole helps kill precancerous cells before they turn malignant. And while boiling carrots wasfound to increase carotenoid levels, another study found that it leads to a total loss of polyphenols, a group ofchemicals found in raw carrots.
Specific polyphenols have been shown to have antioxidant properties and toreduce the risk of cardiovascular disease and cancer, according to a 2005 report in The American Journal ofClinical Nutrition.Comparing the healthfulness of raw and cooked food is complicated, and there are still many mysteriessurrounding how the different molecules in plants interact with the human body. The bottom line, says Liu, is to eatyour veggies and fruits no matter how they're prepared. "We cook them so they taste better," Liu says. "If they tastebetter, we're more likely to eat them." And that's the whole idea. (From Scientific American Online, March 31, 2009)Exercise 7.
What fruits and vegetables are mentioned in the text? Speak about each one and give detailedinformation about the healthy substances it contains and what happens to it after cooking.Exercise 8. Divide into three groups. Each group should read one text (either Text A, B or C) about variouseffects of diet on human health. Then tell other students what you have read about.Text A.
Diet Linked to Twin BirthsBy David BielloOver the last 30 years, the number of twin births has nearly trebled. This rise seems to have followed theintroduction of in vitro fertilization and a preference for having children later in life.
But in the mid-1990s, doctorsbegan limiting the number of embryos transferred in the course of in vitro fertilization and still the proportion of twinbirths rose. Now new research seems to show that bovine growth hormone in the food supply may be responsible.Using data obtained from mothers by way of questionnaire, physician Gary Steinman of the Long IslandJewish Medical Center and his colleagues compared the number of twin births from moms who consumed meatand/or milk and those who consumed no animal products at all. They found that the omnivores and vegetarianswere five times more likely to have fraternal twins than the vegans. In a report published in the current issue of theJournal of Reproductive Medicine, Steinman argues that insulin-like growth factor, a protein released by the liver inresponse to growth hormone, may be the reason. Studies have shown that the protein increases ovulation and thatit persists in the body after entering via digested food, particularly milk.
Drinking a glass of milk a day over a 12week period raised levels of the protein in the body by 10 percent. Vegan women, it turns out, have 13 percentlower concentrations of it in their blood.Steinman observed in the May 6 issue of The Lancet that although the twinning rate in the U.K.--wherebovine growth hormone is banned--rose by 16 percent between 1992 and 2001, it increased by 32 percent in theU.S., where the substance is not banned. Of the new work he says: "This study shows for the first time that thechance of having twins is affected both by heredity and environment or, in other words, by both nature andnurture." (From Scientific American Online, May 22, 2006)Text B.
Diet May Cut Cholesterol As Much As Drugs DoBy Sarah GrahamEating a diet similar to that of our simian relatives can have as much of an effect on cholesterol levels asmodern medicine does, a new study suggests. Results published today in the Journal of the American Medical58Association indicate that a strict, low-fat vegetarian diet high in specific plant products can lower levels of badcholesterol as much as widely prescribed statin drugs can.A number of foods, soy protein and oats among them, have known cholesterol-lowering effects. David J. A.Jenkins of the University of Toronto and his colleagues tested a specific vegetarian diet that combined many ofthese food groups into one menu that contained high amounts of plant sterols, fiber, nuts and soy protein.
Of the 46patients with high cholesterol levels that the team studied, 16 ate this diet for a month. A second group of 16 ate aregular low-fat vegetarian diet and 14 participants consumed the low-fat diet and took 20 milligrams of lovastatin, astandard cholesterol-reducing drug. At the end of the study period, those patients who ate the special diet loweredtheir levels of LDL cholesterol (the "bad" type associated with clogging coronary arteries) by 29 percent whereasthe patients taking lovastatin reduced their LDL levels by 31 percent. The low-fat dieters, in contrast, showed justan 8 percent decrease in the amount of LDL present. "As we age, we tend to get raised cholesterol, which in turnincreases our risk of heart disease," Jenkins explains. "This study shows that people now have a dietary alternativeto drugs to control their cholesterol, at least initially."The results are still preliminary, however.
Writing in an accompanying commentary, James W. Anderson ofthe University of Kentucky notes that if the findings are confirmed by larger and more rigorous studies, they couldhave far-reaching implications for many patients suffering from cholesterol problems. He notes "those who aremotivated to adopt prudent diets might achieve meaningful lipid reductions without pharmacotherapy." (FromScientific American Online, July 23, 2003)Text C. Additive Might Fight Fast-Food FatBy Sarah GrahamIn recent years fast food has been linked to the country's rising obesity rates and the increased incidence ofdiabetes. Findings presented yesterday at the annual meeting of the American Chemical Society in San Diego mayprovide a means of tempering the cuisine's ill effects: an additive that can slow the absorption of fat to a healthierrate.Wallace H.
Yokoyama of the United States Department of Agriculture and his colleagues fed a group ofhamsters a diet with a fat content similar to that of typical American fast food--that is, with about 38 percent of itscalories derived from fat--for four weeks. A second group of animals ate a low-fat diet with 11 percent of the totalcalories coming from fat. At the end of the study period, the high-fat eaters developed insulin resistance--aprecursor to diabetes--whereas the control animals did not.
The initial results corroborated previous findings insimilar studies. But when the scientists repeated the experiment with the addition of a cellulose derivative known ashydroxypropylmethylcellulose (HPMC) to the high-fat food, the animals on that diet did not develop insulinresistance.HPMC is already used as a food additive to modify the texture of items such as fillings, sauces and glazes.To achieve similar fat-fighting results in humans, much larger amounts (about five grams per serving) would berequired, the scientists propose. The mechanism for HPMC's beneficial effects remains unclear, althoughYokoyama posits that the compound works to slow down the absorption of fat by the digestive system.
The results,which are preliminary, are not a panacea for fast-food devotees, however. "Obviously, the less fat you eat, thebetter off you are," Yokoyama says. "But if you're going to eat high-fat foods, then adding HPMC to it might helplimit the damage." (From Scientific American Online, March 16, 2005)Exercise 9.
Summarize all the information about the role of diet discussed in this unit and speak on theeffects of food on human organism.59Section 3. Recommended Report and Presentation Topics1.2.3.4.5.6.7.8.9.10.11.12.13.14.15.16.17.18.19.20.“Out of Africa” migration theory.Hutchinson syndrome.Alzheimer’s disease.Parkinson’s disease.Why do people in the Caucasus traditionally live longer?Age-related transformations in the organism.Anti-age industry.Impaired vision.Wrinkles.Pheromones.The evolutionary role of sexual reproduction.Hermaphrodites.Parthenogenesis.Eating disorders – bulimia, anorexia.Why does fast food taste so good?Health effects of fast food.Dieting.Vegetarians and vegans.Internal organs transformation and alcoholism.Prohibition and legal control of drugs.60.
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