Calcium Update: Another Study Links Dairy Foods With Prostate Cancer

April 1, 2000 -- New data from a long-term study suggest an association between consumption of higher quantities of dietary calcium and risk of prostate cancer. According to the researchers, these findings, presented at the 91st Annual Meeting of the American Association for Cancer Research (AACR), are consistent with the hypothesis that calcium may lower the body's levels of a D vitamin shown to be protective against prostate cancer.

Researchers at Harvard University and Brigham and Women's Hospital in Boston tracked men in the Physicians' Health Study for 11 years. Of the 20,885 men in the study, 1,012 developed prostate cancer. At the beginning of the study, investigators used brief dietary questionnaires to estimate the men's consumption of five dairy products, including milk, cheese and ice cream.

A moderate elevation in risk of prostate cancer was associated with higher intakes of dairy products and dairy calcium, adjusting for other risk factors such as age, smoking, exercise levels, and body mass index. The researchers also found that men who drank more than six glasses of milk per week had lower levels of the potentially protective form of vitamin D than men who drank fewer than two glasses of milk per week.

"For men concerned about prostate cancer, the study suggests a little caution, but it's far too early to recommend any extreme change in eating habits," cautioned June M. Chan, Sc.D., Department of Epidemiology, Harvard School of Public Health, Boston, MA. "More research is needed to confirm these findings, and to clarify the underlying biological mechanisms, such as where in the disease process the calcium may be acting."

"Some data suggest that calcium may play a role in progression from local to metastatic disease," she noted. Dr. Chan and her colleagues will continue investigating the role of calcium in tumor growth.

The researchers acknowledge limitations in the study, such as the fact that the dietary questionnaires did not assess total dietary intake. Additionally, the possible role of calcium supplements was not addressed. Finally, scientists still have an incomplete understanding of all the risk factors involved in development of prostate cancer and how they interact.

See also Fruit versus Calcium, a fuller report on earlier findings, with links to background research.