Supplements vs. exercise for heart disease and cancer
Dietary supplements are wildly popular in America, and it's easy to see why. Because few are regulated by the FDA, manufacturers and retailers can assert many benefits and advertise them aggressively.
But are there other ways to gain the benefits claimed for supplements? Diet and exercise can reduce the risk of many serious diseases, especially when both healthy habits are practiced together.
Here's how exercise and supplements stack up with regard to heart disease and cancer.
Possible protection against cancer is one of the leading reasons that people take supplements in general and antioxidants in particular.
The idea has great appeal. In theory, antioxidants should help counter the harmful effects of free radicals, unstable, high-energy, electrically charged molecules that can damage DNA and cell membranes. Cell damage of this sort could increase the risk of cancer and other diseases. Antioxidants such as vitamin E, vitamin C, and members of the vitamin A–beta carotene family can neutralize free radicals, at least in laboratory experiments.
In the 1980s and early '90s, antioxidants became the great hope against both cancer and heart disease. Sadly, they have been a flop against both .Two major randomized clinical trials found that beta carotene actually increases the risk of lung cancer in smokers. A third study reported that vitamin E increases the risk of second cancers in survivors of head and neck cancer. And a 2007 meta-analysis of 68 randomized clinical trials concluded that beta carotene, vitamin A, and vitamin E, singly or in combination, may actually increase the overall death rate in adults.
The role of supplements in prostate cancer is still being studied. Beta carotene may offer some protection against prostate cancer, but only in nonsmoking men who have very low blood levels due to dietary deficiencies. Selenium, a mineral with antioxidant properties, may reduce a man's risk of prostate cancer. And although many men take supplements of soy or lycopene to reduce their risk of prostate cancer, there is no good evidence that they work. Another ingredient of many popular "prostate supplements" is zinc, which may actually do more harm than good.
Folic acid, a B vitamin, may help reduce the risk of colon cancer, at least in women.
Despite flickers of hope provided by a few studies, the authoritative U.S. Preventive Services Task Force has concluded that vitamin supplements do not reduce the risk of cancer.
If supplements won't protect you against cancer, can you walk away from it? Exercise may reduce the risk of certain common malignancies. Exercise also lowers levels of insulin and various growth factors that appear to stimulate the runaway growth of cancer cells.
The evidence is best for colon cancer. More than 50 studies from around the world show that physically active people are less likely to develop colon cancer than sedentary individuals.
Breast cancer is the other big target of physical activity. More than 60 studies suggest that women who exercise regularly can expect a 20% to 30% reduction in the chance of getting breast cancer, possibly because exercise lowers estrogen levels.
Where does that leave men? The prostate is also responsive to hormones, but in this case the driving force is testosterone. Prostate cancer displays much more clinical variability than most other malignancies, and investigations of exercise and prostate cancer have produced widely varying results. More study is needed.
Evidence is also incomplete for lung cancer and pancreatic cancer, with several studies hinting that exercise can help.
Because they were the greatest hope against heart disease, antioxidants have been the greatest disappointment. But an entirely different group of vitamins has also been investigated.
Until recently, folic acid, B6, and B12 were hopeful candidates for cardiac protection. Either singly, in the case of folic acid, or in combination, these three B vitamins can reduce blood levels of homocysteine, an amino acid. Many studies show that high levels of homocysteine are linked to an increased risk of vascular diseases, including heart attacks, strokes, and blood clots in veins.
But randomized clinical trials of B supplements have failed to demonstrate any protection against heart disease. Further study should shed more light on the question; for now, leafy green vegetables and whole grains rate a resounding "yes" for protection against heart disease, supplements a regretful sigh. At present, the U.S. Preventive Services Task Force does not recommend vitamins to prevent heart disease.
For heart disease, like cancer, good foods outshine supplements. But one supplement can help. People who eat fish regularly, even just twice a week, enjoy a reduced risk of heart attack and sudden cardiac death.
When it comes to reducing the risk of heart disease, exercise is the hands-down winner. Although the details vary, the vast majority of studies agree that regular exercise is associated with a sharp reduction in heart attacks and cardiac deaths; most cite protection in the range of 35% to 55%. Moderate exercise also lowers blood pressure; when performed regularly, it reduces the risk of developing hypertension. No vitamin even begins to claim that important result.December 2007 update