According to Harvard University researchers, too much dietary calcium, like that found in dairy products, can increase the risk of developing prostate cancer, reports HealthWorld.
"This is a 'head's up' rather than the sounding of an alarm," said lead author Dr. June Chan, formerly a researcher at Harvard University Medical School in Cambridge and now assistant professor of epidemiology and urology at the University of California, San Francisco.
For 11 years, the Physicians' Health Study at Harvard gathered health, dietary and lifestyle data from 20,885 male physicians.
Of these men, 1,012 developed prostate cancer.
Dr. Chan and her associates examined data on each man and correlated calcium intake to incidence of prostate cancer.
The investigators created a daily dairy score for each subject, adding up the calcium intake of five common dairy foods: whole milk, skim milk, cold breakfast cereal, cheese and ice cream.
They found the highest 20 per cent of dairy product consumers had a 34 per cent greater risk of prostate cancer.
According to the researchers, dietary calcium increases prostate cancer risk by suppressing the production of 1,25-dihydroxyvitamin D3, the most active form of vitamin D. Other research has identified this form of vitamin D as an inhibitor of prostate cancer cell growth.
They found men who drank more than six glasses of milk a week had lower levels of this form of vitamin D than men who drank fewer than two glasses a week.
"These findings may serve to interject a note of caution into the current enthusiastic promotion of a higher intake of calcium in the United States," the authors wrote.
"There is a growing body of evidence that agrees with our conclusions in this study.
But things have to be kept in balance, especially if there is a family history of particular medical conditions developing with age that might require use of certain diets or supplements," Dr. Chan said.
The National Institutes of Health recommend men younger than 65 years old get 1,000 mg of calcium a day from diet and supplements.
Men over 65 should get 1,500 mg per day.
The NIH also recommend daily calcium intake not exceed 2,000 mg.
The government has noted about half of the American population is estimated to consume less than 600 mg of calcium daily, which has been determined to be inadequate for good health.