Do you know why exercise may protect girls from future breast cancer?

Prof. Know Why answers for your general knowledge and awareness on why exercise may protect girls from future breast cancer:

We are all aware of the fact that exercise is good for health. And middle-aged women have long been advised to get active to lower their risk of breast cancer after menopause. But, starting young, pays off, too. A new research shows, exercise during the teen years — starting as young as age 12 — can help protect girls from breast cancer when they're grown.

Dr. Graham Colditz of Washington University School of Medicine in St. Louis, the study's lead author, points out that the benefit of sustained physical activity from adolescence through the adult years, gets the maximum benefit.

Researchers tracked nearly 65,000 nurses, ages ranging from 24 to 42 who enrolled in a major health study. They answered detailed questionnaires about their physical activity dating back to age 12. Within six years of enrolling, 550 were diagnosed with breast cancer before menopause. A quarter of all breast cancer is diagnosed at these younger ages, when it's typically more aggressive.

Women who were physically active as teens and young adults were 23 percent less likely to develop premenopausal breast cancer than women who grew up sedentary, researchers reported in the Journal of the National Cancer Institute.

The biggest impact was regular exercise from ages 12 to 22.

The women at lowest risk of breast cancer, reported doing 3 hours and 15 minutes of running or other vigorous activity a week — or, for the less athletic, 13 hours a week of walking. Typically, the teens reported more strenuous exercise while during adulthood, walking was most common.

But, why exercise may protect girls from future breast cancer? How exactly, would it help? A big point of exercise in middle age and beyond is to keep off the pounds. After menopause, fat tissue is a chief source of estrogen.

In youth, however, the theory is that physical activity itself lowers estrogen levels. Studies of teen athletes show that very intense exercise can delay onset of menstrual cycles and cause irregular periods.

While the study examined only premenopausal breast cancer, "it's certainly likely and possible" that the protection from youthful exercise will last long enough to affect more common postmenopausal breast cancer, too, Colditz added.

Dr. Alpa Patel, a cancer prevention specialist at the American Cancer Society, who praised the new research, said that though the moderate exercise reported in this study of breast cancer was nowhere near enough for those big changes, but it probably was enough to cause slight yet still helpful hormone changes.

Dr. Patel believes that even if someone was a bookworm as a teen, it's not too late, because other researches on the middle-age benefits of exercise show, mom should join her daughters for that bike ride or game of tennis or at least a daily walk around the block.

There are quite a few breast cancer risks that a woman can't change, like:

• How early she starts menstruating
• How late menopause hits
• Family history of the disease

But, physical activity and body weight are such factors that women can control. Women who engage in physical activity not only during adolescence but also during adulthood, lower their risks of breast cancer, said Dr. Patel.

So, what are you still waiting for? If your young daughter is a bookworm or simply a TV buff, just simply get her off the couch.

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Do you know why we laugh?

Prof. Know Why explains:

The reasons we laugh, including ‘contagious’ laughter, may be products of evolution. Natural laughter is a two-part, spontaneous, response to humor, that has physiological, psychological, and physical benefits. Most agree that we laugh when we find something to be humorous, though different reasons exist for what we find to be humorous. Additionally, different things are humorous to us at different stages of life.

Laughter, a physiological response to humor, can be broken down into two parts. The first is a set of gestures, and the second is the production of sound. The brain forces to conduct both responses simultaneously.

From a physiological standpoint, a ‘sensor’ in the brain responds to laughter by triggering other neural circuits in the brain, which, in turn, generate more laughter. Oddly enough, laughter is an orderly response, and almost occurs spontaneously during pauses at the end of phrases, earning it the name the ‘punctuation effect’. Human beings are the only species capable of laughter, and an average adult does so approximately 17 times per day.

Scientists say that laughing is a great exercise and estimates that laughing 100 times is equivalent to a 10-minute workout on a rowing machine, or 15 minutes on a stationary exercise bike.