Researchers from Boston, Massachusetts, USA, examined the association between calcium intake and colon cancer risk in two prospective cohorts.
The study included 87,998 women in the Nurses' Health Study (NHS) and 47,344 men in the Health Professionals Follow-up Study (HPFS).
At baseline (1980 for NHS and 1986 for HPFS), the individuals completed a food frequency questionnaire and provided information on medical history and lifestyle factors.
Dietary information was updated at least every 4 years.
During the follow-up period (1980-96 for NHS and 1986-96 for HPFS), 626 and 399 colon cancer cases were identified in women and men, respectively.
In women and men considered together, the investigators found an inverse association between higher total calcium intake (>1250 mg/day versus ≤500 mg/day) and distal colon cancer. The multivariate relative risk (RR) for women and men was 0.73 and 0.58, respectively. The pooled RR was 0.65.
No such association was found for proximal colon cancer (women: RR = 1.28; men: RR = 0.92; pooled RR = 1.14).
However, the incremental benefit of additional calcium intake beyond approximately 700 mg/day appeared to be minimal.
| Higher calcium intake reduced risk of distal, but not proximal, colon cancer.
| Journal of the National Cancer Institute |
Kana Wu, of the Harvard School of Public Health, Boston, said on behalf of the group, "Higher calcium intake is associated with a reduced risk of distal colon cancer.
"The observed risk pattern was consistent with a threshold effect, suggesting that calcium intake beyond moderate levels may not be associated with a further risk reduction."
"Future investigations on this association should concentrate on specific cancer subsites and on the dose-response relationship," it was concluded.