Calcium as a chemopreventive agent against colorectal neoplasm: does obesity play a role?

Abstract

In our study-level meta-analysis, we found no evidence to support that the chemopreventive potential of calcium, if real, may be stronger in leaner individuals.

Body mass index, calcium supplementation and risk of colorectal adenomas

“…27 When colon and rectal cancer were examined separately, the benefit of calcium appeared to be confined to studies with populations with higher average BMI (≥ 25 kg/m 2 ) at both sites, in apparent contradiction to our results, although the heterogeneity in the findings by population BMI was not statistically significant. 27 An important limitation of this work was the analysis of population average BMIs instead of participant-level BMI data. 27 The reason(s) why the findings from these analyses of observational data differ from ours are unclear but could be related to confounding of calcium intake or imprecision in the measurement of BMI or calcium intake in the meta-analyses.…”

“…In this work, when studies were classified based on the average BMI of the study populations into two groups (BMI < 25 kg/m 2 and BMI ≥ 25 kg/m 2 ), no significant evidence of heterogeneity by population BMI was found . When colon and rectal cancer were examined separately, the benefit of calcium appeared to be confined to studies with populations with higher average BMI (≥ 25 kg/m 2 ) at both sites, in apparent contradiction to our results, although the heterogeneity in the findings by population BMI was not statistically significant . An important limitation of this work was the analysis of population average BMIs instead of participant‐level BMI data .…”

“…Second, motivated by our findings, Keum et al re‐examined meta‐analytical data on the inverse associations of calcium intake with adenomas and CRC from prospective observational studies . In this work, when studies were classified based on the average BMI of the study populations into two groups (BMI < 25 kg/m 2 and BMI ≥ 25 kg/m 2 ), no significant evidence of heterogeneity by population BMI was found . When colon and rectal cancer were examined separately, the benefit of calcium appeared to be confined to studies with populations with higher average BMI (≥ 25 kg/m 2 ) at both sites, in apparent contradiction to our results, although the heterogeneity in the findings by population BMI was not statistically significant .…”

“…First, in a combined analysis of results from the Nurses’ Health Study and the Health Professionals Follow‐up Study, total calcium intake appeared to be associated with the largest decrease in risk of distal colon cancer among those individuals with the highest BM (>30 kg/m 2 ), but effect modification by BMI was not statistically significant ( p interaction = 0.15) . Second, motivated by our findings, Keum et al re‐examined meta‐analytical data on the inverse associations of calcium intake with adenomas and CRC from prospective observational studies . In this work, when studies were classified based on the average BMI of the study populations into two groups (BMI < 25 kg/m 2 and BMI ≥ 25 kg/m 2 ), no significant evidence of heterogeneity by population BMI was found .…”

“…27 An important limitation of this work was the analysis of population average BMIs instead of participant-level BMI data. 27 The reason(s) why the findings from these analyses of observational data differ from ours are unclear but could be related to confounding of calcium intake or imprecision in the measurement of BMI or calcium intake in the meta-analyses. Importantly, our studies utilized randomized assignments to a clearly defined calcium supplement (calcium carbonate, providing 1,200 mg/day elemental calcium).…”