Moderate daily consumption of around 700mg of calcium could be effective in fighting colon cancer, according to a recent study by researchers at the Harvard School of Public Health in Boston.
Writing in the 20 march issue of the Journal of the National Cancer Institute, Dr Kanu Wu said his team of researchers had shown that this moderate intake of calcium could be effective in reducing the risk of colon cancer, but that consuming more than this amount seemed to have no significant additional benefits.
Dr Wu said that earlier studies of calcium intake and the risk of colon cancer had been inconsistent, with most showing some modest benefits. The Harvard study looked more closely at these modest associations, and showed statistically significant links.
The team studied 87,998 women in the Nurses' Health Study (NHS) and 47,344 men in the Health Professionals Follow-up Study (HPFS). During follow-up - a period of 16 years in the NHS cohort and 10 years in the HPFS cohort - 626 women and 399 men developed colon cancer. In pooled analyses, men and women with a calcium intake of 701 to 800 mg/day or higher, derived from diet or supplements, had about a 40 per cent to 50 per cent lower risk of distal colon cancer compared with those who consumed 500 mg/day or less of calcium, the team showed. Calcium intake did not influence the risk of proximal colon cancer in this study.
According to the researchers, the results "were consistent with a threshold effect of calcium intake on colon cancer risk, suggesting that even a modest increase in calcium intake may confer protection against distal colon cancer among those with low intakes".
The study also showed that the positive effects of calcium on colon cancer risk was strongest among male smokers. It did not occur among patients taking aspirin, Dr Wu said.