Previous studies have found that the consumption of dairy foods – which are the primary source of calcium in Western diets – is linked to prostate cancer. The current research aimed to test whether calcium, as opposed to other dairy components, is responsible for the association of dairy foods with prostate cancer.
"Our results support the notion that calcium plays a risk in enhancing the role of prostate cancer development. This study is the first to report an association at such low levels and among primarily non-dairy foods," said lead researcher Lesley Butler, assistant professor of epidemiology at Colorado State University, Fort Collins, Colo.
Published this month in Cancer Research, a journal of the American Association for Cancer Research, the study examined calcium intake and prostate cancer risk among 27,293 men in the Singapore Chinese Health Study that was established between 1993 and 1998 and funded by the US National Institutes of Health, National Cancer Institute.
The researchers chose this population because in the Asian diet the main contributors of calcium intake are non-dairy foods such as tofu, grains and vegetables such as broccoli, kale and bok choy.
Their findings confirmed a negative health impact of these foods, even at relatively low levels of consumption.
The researchers used a food frequency questionnaire to assess diet at baseline. They also adjusted results to account for body mass index as calcium is thought to have higher absorption in smaller individuals.
Of the men participating in the study, 298 were diagnosed with prostate cancer. Results showed a 25 percent increased risk of prostate cancer when comparing those who consumed, on average, 659mg versus 211mg of total calcium a day. Among men with less than average BMI, the researchers found a twofold increased risk of prostate cancer.
Vegetables were the largest contributor of daily calcium intake in the study population (19.3 percent), followed by dairy (17.3 percent), grain products (14.7 percent), soyfoods (11.8 percent), fruit (7.3 percent) and fish (6.2 percent).
The researchers stressed that there was no positive association with prostate cancer risk and any one particular food source. They said that more studies are needed to examine the role of calcium, as opposed to other dairy components, in prostate cancer.
Calcium Intake Increases Risk of Prostate Cancer among Singapore Chinese
Cancer Research, 10.1158/0008-5472.CAN-09-4544
Authors: Lesley M. Butler, Alvin S. Wong, Woon-Puay Koh, Renwei Wang, Jian-Min Yuan, and Mimi C. Yu