In light of a recent meta-analysis in which vegans had a higher risk of rectal cancer, we reinforced our recommendation that vegans should aim to meet the RDA for calcium; see Cancer Meta-Analysis (Another One!). To ensure this guidance was well-founded, I reviewed the strength of the evidence connecting higher calcium intakes to reduced colorectal cancer risk. Here’s the summary:
Higher calcium intake — ideally around 1,000 mg/day — is consistently associated with lower colorectal cancer risk in observational studies, and the World Cancer Research Fund rates the evidence for causality as “probable.” Randomized trials have been largely disappointing, however, possibly because they’re too short to capture a process that unfolds over decades or because participants already have adequate calcium intakes at baseline. For vegans, who often fall below 700 mg/day, aiming for closer to 1,000 mg/day is worth prioritizing for bone health and could also protect against colorectal cancer.
See the details in Calcium and Colorectal Cancer.
