"An ounce of prevention is worth a pound of cure."
For a young girl the above phrase underlines the importance of exercise. Why? Because recent research has presented proof that a woman who exercises at least four hours a week during her reproductive years will have cut in half her chances of getting breast cancer.
The woman who led this research effort was Leslie Berman, Ph.D., and holder of the AFLAC Chair in Cancer Research at the Keck School of Medicine, located on the Health campus of the University of Southern California. Several years ago Dr Berman read some reports from epidemiologists, reports that linked breast cancer risk to ovarian hormones such as estrogen and progesterone. Having once been a competitive swimmer, Dr. Berman knew that intensive exercise could cause ovarian hormone levels to plummet, sometimes affecting the regularity with which the exercising female had periods.
Dr. Berman formed a hypothesis. She discussed her hypothesis with her colleagues. The hypothesis was that the lower hormone levels achieved by exercise might lower the risk that a woman will get breast cancer.
The effort to prove that hypothesis began with the recruitment of 500 breast cancer survivors, age 40 or younger, plus a matching group of women without breast cancer. Project questioners asked each of the women to provide details about their exercise habits. The researchers sought information about both outdoor rigors such as jogging and indoor activities such as dancing.
The results of this research appeared in the November 2003 issue of Cancer. The results were proof that women who exercised had a 35 per cent lower risk of developing breast carcinoma in situ (BCIS) than did women who remained inactive. Breast cancer in situ is the name that clinicians give to the clusters of malignant cells that can form in breast ducts or lobules.
Clinicians who have young female patients got even more valuable information. They learned that exercise during the teenage years might hold an added value to the dropping of ovarian hormones. Dr. Berman underscores the fact that cells in the breast ducts, the site of most breast cancers, grow fastest during adolescence. Scientists thus believe that lowering the cells' exposure to ovarian hormones during that period of greatest cell growth might be especially important as a protection against breast cancer.
In other words, the estrogen and progesterone, which naturally circulates through the body of a young woman, stimulates breast cells to divide. A great many divisions lead to dense breast tissue. Dense breast tissue appears to be an indication that a woman has an increased breast cancer risk.
If a woman devotes just four hours a week to active exercise, she has provided herself with protective effects that could last a lifetime. By the time that she reaches menopause, Dr. Berman and other researchers could have sorted out the many polymorphisms (the specifics of the DNA) that place some women in the category of "greatest risk of getting breast cancer." Such scientists might have found out by then how to test women in the upper age range, determining whether or not their genetic make-up will allow them to safely use hormone replacement therapy.