Calcium is an important part of a healthy diet, but it's true that some research has linked high levels of dietary calcium to an increased risk of prostate cancer.
Studies performed about a decade ago first showed a connection between high intake of dairy products and prostate cancer. Initially this was felt to be due to the high levels of saturated fat found in many dairy products, but subsequent research suggested it was the calcium, not the fat, that was the culprit.
More recent studies have continued to find a link between calcium and prostate cancer. For example, a study from Seattle found that men with highest levels of calcium intake -- more than about 1,200 mg per day -- had up to double the risk of being diagnosed with advanced prostate cancer. Other studies, such as Harvard-based Physician's Health Study, found that higher levels of calcium increased the risk of prostate cancer, but only by 20 to 30 percent. Other researchers have concluded that moderate levels of calcium intake appear to have little or no impact on cancer risk.
To further complicate matters, studies have linked calcium supplements to a decreased risk of colon polyps and colon cancer. There is also evidence that vitamin D -- which is found in dairy products, and is often given together with calcium -- helps to lower the risk of prostate cancer.
More research will be needed to sort out the exact relationship between prostate cancer and different dietary factors, including calcium, vitamin D, and antioxidants such as vitamin E, lycopene and selenium. For now, it seems reasonable to advise the following:
Most men should avoid taking more than 1,200 mg of calcium per day, unless there is a medical reason to do so (for example, known osteoporosis).
On the other hand, getting moderate amounts of calcium -- in the range of 600 to 1,000 mg daily -- is a reasonable way to protect against bone loss, and might help to prevent colon cancer.
Taking a multivitamin with at least 400 international units (IU) of vitamin D may help to offset some of the negative effects from dietary calcium, and will work together with calcium to prevent bone loss.
Avoiding saturated fats, getting regular exercise, and eating lots of fresh fruits and vegetable may also help to lower the risk of a variety of different types of cancer.
