Only about five years ago, every patient of mine who finished chemotherapy was given a vitamin cocktail to further reduce colon cancer risk. It was calcium, selenium, vitamin E and folic acid.
Over the last three years, folic acid has been shown to increase growth of polyps, and in patients with metastatic disease it may shorten life. The protective value of vitamin E has been questioned, and there was evidence that it might increase prostate cancer risk. Selenium did not show benefit.
So we are down to calcium. This supplement has been shown repeatedly to benefit patients by reducing cancer risk for a variety of solid tumors including colon cancer. A recent publication by Dr. Yikyung Park from the National Cancer Institute showed that supplementation of 1200 mg calcium in women and men over the age of 50 decreased cancer risk by 17% for men and 23% for women (Archives of Internal Medicine, February 23, 2009). These were cancers of the gastrointestinal tract mainly colon cancers.
The usual source for calcium in our diet is milk products (yogurt, cheese, etc) as well as meat. The calcium pathway is very interesting because it requires activity of vitamin D. Without vitamin D it is difficult to absorb calcium and put it into the organs where we need it, but to make sure we have sufficient vitamin D we need some sun exposure (vitamin D is activated in the skin) and we need a functional kidney.
When vitamin D was tested in patients with colon cancer it was found by Dr. Charles Fuchs in the Journal of Clinical Oncology published in June last year that the patients with the highest vitamin D levels lived longer suggesting that low levels may be associated with shorter survival. Since there are very rare side effects from either vitamin D or calcium supplementation, I recommend all my patients take 1500 mg of calcium and 1000-3000 units of vitamin D daily.
I have one funny story from one of my patients giving him the spiel of calcium supplementation which he loved and started right away. About three months later he was admitted with kidney stones. He had inflammatory bowel disease which has higher risk of kidney stones which was further aggravated by calcium supplementation. Therefore if you have a history of kidney stones or inflammatory bowel disease please check with your doctor first before starting calcium supplements.