Exercise and cancer
The daily walk can even lower the risk of cancer
YOUR DAILY walk may do more than cut the risk of heart disease, Non-Insulin-Dependent Diabetes Mellitus and hypertension. It may decrease the risk of cancer, particularly colon cancer.
The first hint of exercise's beneficial role in cancer prevention came in a study in the 1920s. However, it took the explosion of knowledge in the field of cancer biology and cancer genetics in the last 50 years to permit the formulation of a plausible hypothesis to explain the moderate
decrease in cancer incidence in active subjects.
"Moderate" is the key word here. A lifestyle excluding tobacco and alcohol, staying out of the sun, eating lots of fresh fruit daily, and eating less saturated fat have the biggest benefit in terms of lowering overall cancer risk. For example, eliminating smoking and alcohol consumption would prevent a third of all cancers in the human race.
Exercise may help prevent cancer by enhancing the immune system. Research suggests that a moderate level of physical activity enhances immunity, while intense exercise decreases it. This means that walking is better at lowering overall cancer risk than sprinting or marathon running.
Other biological mechanisms may operate in site-specific cancers like colon cancer. Sedentary men have 1.6 times the risk of colon cancer when compared with men who exercise regularly. Apart from lowered body fat, a possible explanation of the lowered risk is that exercise speeds up the transit of food through the gut. One way exercise accomplishes this is by increasing local synthesis of prostaglandins. Faster intestinal transit decreases the amount of contact between carcinogens in the food and the inner lining of the gut.
A few studies indicate that exercise decreases the risk of breast cancer, but data is too sparse to prove a link conclusively. One study showed that non-athletes had nearly two times the risk when compared with athletes. Exercise causes changes in hormone levels in addition to decreasing body fat, and this may be a possible explanation of the anti-cancer effect. However, the link between exercise and breast cancer-prevention needs to be studied further and validated by betterresearch to be widely accepted.
Exercise appears to be unrelated to rectal cancer risk. Women who are sedentary have a greater risk of developing cancer of the uterus, cervix, vagina, and ovary, but as with breast cancer there is no proven explanation of the inverse association between physical activity and these cancers.
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