The study, presented earlier this month at the American Association for Cancer Research's annual cancer prevention meeting, was based on 17 years of follow-up and 1269 incident cases of prostate cancer identified in theAlpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study.
Analysis of the data revealed that men who consumed more than 2000mg of calcium per day nearly doubled their risk of developing prostate cancer.
The findings could have implications for the dietary supplements industry, as well as mainstream foods, increasingly fortified with calcium in a bid to protect bones from the growing risk of osteoporosis.
The researchers noted that the risk of prostate cancer seemed to be clearly linked to calcium, and not overall dairy intake. Although dairy product intake increased the risk of prostate cancer, no association remained after controlling for calcium.
And with the exception of cream, which showed a significant trend toward an increased prostate cancer risk across intake levels, other individual dairy products showed no association.
Nor was there any evidence of a link for intake of vitamin D or phosphorous.
Panagiota Mitrou from the National Cancer Institute, and lead author of the study, said: "These results might explain the positive association seen with dairy products in our previous studies. Further research should focus on how dietary calcium could affect prostate cancer."