Calcium can reduce the risk of colorectal tumors by binding secondary bile and fatty acids, which leads to antiproliferative effects in the bowel.
Alternatively calcium can act directly on the colonic epithelium, which affects differentiation and apoptosis.
Researchers in America, lead by Ulrike Peters, undertook a study to investigate calcium intake and risk of colon adenoma in order to evaluate the association of calcium intake with early stages of colorectal tumor development.
The investigators examined the supplemental and dietary calcium intakes of 3696 participants with histologically verified adenoma of the distal colon (ie, descending colon, sigmoid colon, or rectum).
The research team then compared these data with the calcium intakes of 34 817 sigmoidoscopy-negative control participants in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.
|Adenoma risk was lower by 12% for participants in the highest quintile of total calcium intake|
|American Journal of Clincal Nutrition|
The researchers assessed calcium intake at study entry with a 137-item food-frequency questionnaire.
The research team also asked additional questions on the amount and duration of calcium supplement use.
After adjustment for known risk factors, the researchers found that adenoma risk was lower by 12% for participants in the highest quintile of total calcium intake (>1767 mg/d) than for participants in the lowest quintile (<731 mg/d).
The research team noted that this protective association between total calcium and colorectal adenoma was largely due to calcium supplement use.
The researchers found a 27% decrease in adenoma risk for participants taking >1200 mg/d than for nonusers of supplements.
Dr Peters commented, "The protective associations of total and supplemental calcium were strongest for colon adenoma (descending and sigmoid colon)."
She concluded, "High calcium intake, particularly from supplements, is associated with a reduced risk of distal colorectal adenoma."