听力Section B
Passage 2
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Most Americans don’t eat enough fruits, vegetables or whole grains, researchers now says adding fiber to teen diet may help lower the risk of breast cancer.

Conversations about the benefits of fiber are probably more common in nursing homes than high schools. But along comes a new study that could change that. Kristi King，a diet specialist at Texas Children's Hospital finds it's hard to get teenager patients’ attention about healthy eating but telling them that eating lots of high-fiber foods could reduce the risk of breast cancer before middle age. That's a powerful message.

The new finding is based on a study of 44,000 women. They were surveyed about their diets during high school, and their eating habits were tracked for two decades. It turns out that those who consumed the highest levels of fiber during adolescence had a lower risk of developing breast cancer, compared to the women who ate the least fiber. This important study demonstrates that the more fiber you eat during your high school years, the lower your risk is in developing breast cancer in later life.

The finding points to long-standing evidence that fiber may reduce circulating female hormone levels, which could explain the reduced risk. The bottom line here is the more fiber you eat, perhaps, a lower level of hormone in your body, and therefore, a lower lifetime risk of developing breast cancer. High-fiber diets are also linked to a reduced risk of heart disease and diabetes. That's why women are told to eat 25 grams a fiber a day - men even more.

Q13. What does the new study tell about adding fiber to the teen diet?
Q14. What do we learn about the survey of the 44,000 women?
Q15. What explanation does the speaker offer for the research finding?