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CALCIUM, a necessary part of the diet to build strong bones and teeth, may increase prostate cancer risk in men who are of small build, a recent study found.
The study also found that even at relatively low levels and from non-dairy foods such as soya, grains and green vegetables, calcium significantly increases the risk among Chinese men.
The data for the research, published this month in Cancer Research, a journal of the American Association for Cancer Research, was taken from the Singapore Chinese Health Study of more than 63,000 ethnic male Chinese living here and aged between 45 and 74.
Conducted by the National University of Singapore (NUS) department of community, occupational and family medicine, the study began in 1993, when all the subjects were cancer-free.
Researchers assessed whether dietary calcium increased prostate cancer risk in over 27,000 Chinese men with low dairy consumption.
It was found that the major food sources of calcium in this group comprised vegetables, dairy and grain products, soya foods, fruit and fish.
Of these men, about 300 were diagnosed with prostate cancer but the scientists said there was no one particular food source that could be associated with prostate cancer risk.
Principal investigator Lesley Butler, an assistant professor of epidemiology at Colorado State University, said that since smaller individuals absorbed calcium better, the researchers also accounted for body mass index (BMI) in this Chinese population.
They found that men with a BMI of 22.9 face twice the risk of getting prostate cancer. A BMI of 18.5 to 24.9 is considered to be in the healthy range for Caucasians. According to the Health Promotion Board in Singapore, the healthy range for Asians is between 18.5 and 22.9.
Dairy products are the primary sources of calcium in Western diets, while in an Asian diet, non-dairy foods are the major contributors of calcium.
Earlier studies looking at the connection between calcium from dairy products and prostate cancer risk found a definite link to the cancer.
Associate Professor Koh Woon Puay of the Yong Loo Lin School of Medicine in NUS told The Straits Times that low calcium intake is associated with low bone mass, bone loss and higher fracture rates and warned that more scientific proof on the cancer-calcium link is needed 'before the evidence can be considered convincing'.
'We need more data from other Asian populations, where dietary calcium comes mainly from non-dairy sources, to confirm the findings we have reported,' she said.
Dr Chau Noan Minh, a consultant with the Department of Medical Oncology at the National Cancer Centre, added that while it is not possible to give specific dietary advice to men about calcium-containing foods, 'a study with a larger number of people would be needed to understand how high calcium intake in those with lower BMI results in a higher risk of developing prostate cancer'.
juditht@sph.com.sg
This article was first published in The Straits Times.
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