Exercise May Help Reduce Breast Cancer Risk
There is growing evidence that exercise is an important weapon in the fight against breast cancer. This is good to know because the Department of Health has stated that the disease is the leading cancer in Filipino females.
Studies conducted in five countries and three continents indicate that the higher the level of daily physical activity, the lower the risk of breast cancer. Women who had the highest risk were those who sat for long periods at home or in the office on a daily basis.
The “physical activity” that was measured in the studies included things like walking, lifting, climbing stairs, standing, moving from site to site and manual work (housework and gardening) as well as moderate to vigorous “formal” exercise and recreational sports like aerobic classes, weight lifting, tennis, swimming, running, and cycling.
A 14-year Norwegian study found that those who exercised four hours a week had a 37% lower risk than sedentary women. The risk was lowest in lean women, women under the age of 45, and women who continued to exercise regularly for three to five years.
However, even elderly women in their 70’s can reduce their risk compared to sedentary women of the same age if they exercised several times a week according to an 11-year study done by the Mayo Clinic.
It seems that a little exercise is better than none. A 2005 University of Southern California study compared lifestyle habits of women who had breast cancer and women who did not. There was a 20-percent lower risk for women who had exercised at least 1.3 hours a week since the age of ten. But, the study found that exercise did not reduce the risk for women who had a family history of breast cancer (first degree family member – mother, sister, daughter).
Scientists are not sure exactly how exercise reduces the risk of breast cancer but the main theory has to do with estrogen. Since reproductive cancers are estrogen-related, exercise may be protective because it reduces lifetime exposure to estrogen by lowering body fat levels (the more fat you have, the higher your estrogen level) and reducing estrogen levels circulating in the blood.
The body fat in postmenopausal women converts male hormones called androgens (produced by a woman’s adrenal glands) into estrone, a particularly potent form of estrogen, says Dr. Christine Wells who has reviewed more than ten years worth of studies on breast cancer and exercise. She says there is substantial evidence that elevated estrone levels are associated with an increase in breast cancer in postmenopausal women.
A Harvard School of Public Health study showed that if a woman is more than 44 pounds overweight when she reaches menopause she has double the risk of breast cancer compared to a woman of normal weight. There is a 60% risk if 22 to 44 pounds overweight and a 20% risk with 5 to 22 pounds of excess weight.
Another study done at the Moffitt Cancer Center and Research Institute in Tampa, Florida calculated the risk of breast cancer in women who were overweight at the age of 30. They found that being ten pounds overweight had a 23% risk, 15 pounds overweight a 37% risk and 20 pounds overweight a 52% risk compared to being of normal weight.
The National Cancer Institute studied 1,500 U.S. women of Asian descent and discovered that the women who were most overweight in their 40’s and 50’s had double the risk of breast cancer. The women who were over fifty years old and had gained ten pounds since they were forty had triple the risk compared to women whose weight had stayed the same. The good news is that women who used to be overweight when they were young but lost weight by their fourth and fifth decade did not increase their risk of breast cancer.
Other studies have indicated that there is a greater risk for women who become overweight as an adult but not for women who were overweight since childhood. Also, fat in the waist may increase risk more than the same amount of fat in the hips and thighs.
The second theory is that exercise enhances a woman’s immune system to effectively fight off cancer cells before they can cause real damage.
Finally, women who exercise tend to have healthier lifestyle habits (good nutrition, moderate alcohol, no smoking, enough sleep) than women who are sedentary and this might make all the difference.
Whatever theory proves to be true (or maybe all three are right), the important thing is that all women should become more physical active to help lower their risk of breast cancer.
Even women with breast cancer can benefit from exercise. A 2005 study, the first of its kind, found that exercise of three to five hours a week, while not an iron-clad guarantee of survival, increased the odds of surviving the disease. Even one hour of exercise a week helped. It was the women with estrogen-sensitive breast cancer who benefited the most, which strengthens the theory of the estrogen connection.
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