Milk can do more than build strong bones; it may also create resistance to colorectal cancer. Years of studies have looked at the link between calcium and colon cancer, the third most common type of cancer. Two new studies, one led by doctors at Dartmouth Medical School and the other led by doctors from Brigham and Women's Hospital and Harvard Medical School, come to the conclusion that milk does a body good in more ways than one.

What the researchers wanted to know: Does calcium intake affect the risk of colon cancer?

What they did: The Dartmouth-led study used data from more than 900 people who had had a colorectal growth removed at least three months before they began the study. The participants swallowed either a calcium supplement or a placebo pill for an average of four years and returned after one year and after four years for follow up examinations. The second study did not test new patients but instead combined and reinterpreted data from previous studies. Researchers used information about the diets of more than 500,000 people from all over the world, nearly 5,000 of whom developed colorectal cancer. They examined data from 10 different studies to see whether milk consumption, consumption of other types of dairy foods, and total calcium intake affected the rate of colorectal cancer.

What they found: Both studies found that calcium decreases the risk of colon and rectal cancer but were cautious about saying that calcium helps in every case. In the first study, calcium supplements abated the growth of the most advanced type of colorectal lesion, considered to be at high risk of turning into cancer. Calcium had an effect on more benign growths as well, but it was not as pronounced.

In the second study, the doctors found that milk consumption reduced the risks of rectal cancer and cancer of the distal colon (the part closer to the rectum). Milk reduced the risk of colon cancer more than other calcium-laden foods such as yogurt or cheese; one glass of milk per day, containing about 250 grams of calcium, reduced colon cancer risk by about 15 percent.

What it means to you: The moral of both studies: Drink lots of milk and get calcium where you can, especially if you have a family history of colorectal cancer. Both of these studies showed significant improvements from doses of calcium and especially from milk, which has additional proteins that doctors think may prevent abnormal growths in the colon and rectum. Previous studies have also shown a link between calcium and colon cancer.

Caveats: Because these two studies used different methods to come to the same conclusion, the different limitations of each study can be overlooked to a certain extent. Still, in the Dartmouth study, the doctors examined only patients who had a history of abnormal colon growths, which could mean that they reacted differently to calcium supplements than other people. In the Brigham Hospital study, the researchers looked at different aspects of diet but had a harder time isolating the effects of calcium itself. Milk may have come out as the best vehicle for calcium just because it has a higher concentration than other dairy products.

Find out more: A short history of the attempt to tie colon cancer and calcium together, along with some links where you can get more information, is available on the MedicineNet website at http://www.medicinenet.com/

The National Institutes of Health has a colorectal cancer site with information about treatment and prevention, including diet information. http://www.nci.nih.gov/

Read the article: Wallace, K., Baron, J.A., Cole, B.F., Sandler, R.S., Karagas, M.R., Beach, M.A., Haile, R.W., Burke, C.A., Pearson, L.H., Mandel, J.S., Rothstein, R., Snover, D.C. "Effect of Calcium Supplements on the Risk of Large Bowel Polyps." Journal of the National Cancer Institute, June 16, 2004. Vol. 96, No.12, pp. 921–925.

Eunyoung, C. et al. "Dairy Foods, Calcium and Colorectal Cancer: A Pooled Analysis of 10 Cohort Studies." Journal of the National Cancer Institute. July 7, 2004, Vol. 96, No. 13, pp. 1015–1022.