Exercise 7. What fruits and vegetables are mentioned in the text? Speak about each one and give detailed information 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 various effects of diet on human health. Then tell other students what you have read about.

Text A. Diet Linked to Twin Births

By David Biello

Over the last 30 years, the number of twin births has nearly trebled. This rise seems to have followed the introduction of in vitro fertilization and a preference for having children later in life. But in the mid-1990s, doctors began limiting the number of embryos transferred in the course of in vitro fertilization and still the proportion of twin births 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 Island Jewish Medical Center and his colleagues compared the number of twin births from moms who consumed meat and/or milk and those who consumed no animal products at all. They found that the omnivores and vegetarians were five times more likely to have fraternal twins than the vegans. In a report published in the current issue of the Journal of Reproductive Medicine, Steinman argues that insulin-like growth factor, a protein released by the liver in response to growth hormone, may be the reason. Studies have shown that the protein increases ovulation and that it persists in the body after entering via digested food, particularly milk. Drinking a glass of milk a day over a 12-week period raised levels of the protein in the body by 10 percent. Vegan women, it turns out, have 13 percent lower 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.--where bovine growth hormone is banned--rose by 16 percent between 1992 and 2001, it increased by 32 percent in the U.S., where the substance is not banned. Of the new work he says: "This study shows for the first time that the chance of having twins is affected both by heredity and environment or, in other words, by both nature and nurture." (From Scientific American Online, May 22, 2006)

Text B. Diet May Cut Cholesterol As Much As Drugs Do

By Sarah Graham

Eating a diet similar to that of our simian relatives can have as much of an effect on cholesterol levels as modern medicine does, a new study suggests. Results published today in the Journal of the American Medical Association indicate that a strict, low-fat vegetarian diet high in specific plant products can lower levels of bad cholesterol 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 of these food groups into one menu that contained high amounts of plant sterols, fiber, nuts and soy protein. Of the 46 patients with high cholesterol levels that the team studied, 16 ate this diet for a month. A second group of 16 ate a regular low-fat vegetarian diet and 14 participants consumed the low-fat diet and took 20 milligrams of lovastatin, a standard cholesterol-reducing drug. At the end of the study period, those patients who ate the special diet lowered their levels of LDL cholesterol (the "bad" type associated with clogging coronary arteries) by 29 percent whereas the patients taking lovastatin reduced their LDL levels by 31 percent. The low-fat dieters, in contrast, showed just an 8 percent decrease in the amount of LDL present. "As we age, we tend to get raised cholesterol, which in turn increases our risk of heart disease," Jenkins explains. "This study shows that people now have a dietary alternative to drugs to control their cholesterol, at least initially."

The results are still preliminary, however. Writing in an accompanying commentary, James W. Anderson of the University of Kentucky notes that if the findings are confirmed by larger and more rigorous studies, they could have far-reaching implications for many patients suffering from cholesterol problems. He notes "those who are motivated to adopt prudent diets might achieve meaningful lipid reductions without pharmacotherapy." (From Scientific American Online, July 23, 2003)