A landmark study published in JAMA Network Open has demonstrated a significant protective association between increased calcium intake and reduced colorectal cancer (CRC) risk, offering new insights into potential dietary strategies for cancer prevention.
The extensive analysis, drawing from the National Institutes of Health-AARP Diet and Health Study, followed 471,396 initially cancer-free participants over a median period of 18.4 years. The study documented 10,618 first primary colorectal cancer cases across 7.3 million person-years of follow-up.
Key Findings and Risk Reduction
Participants in the highest quintile of calcium intake demonstrated a striking 29% lower risk of developing colorectal cancer compared to those in the lowest quintile (HR, 0.71; 95% CI, 0.65-0.78; P < .001). The protective effect was observed consistently across different tumor sites and calcium sources.
Daily calcium intake varied substantially among participants:
- Lowest quintile (Q1): 401 mg/day for women, 407 mg/day for men
- Highest quintile (Q5): 2,056 mg/day for women, 1,773 mg/day for men
Sources of Calcium Protection
The study identified three main sources of calcium intake:
- Dairy products: 42.1%
- Non-dairy sources: 34.2%
- Dietary supplements: 23.7%
All sources showed protective associations against colorectal cancer development, suggesting multiple viable pathways for increasing calcium intake.
Demographic Considerations and Health Equity
While non-Hispanic Black participants showed similar patterns of calcium intake variation (382 mg/day to 1,916 mg/day between lowest and highest quintiles), the association between calcium intake and CRC risk did not reach statistical significance in this group (HR, 0.60; 95% CI, 0.32-1.13; P = .12). However, researchers noted no evidence of effect modification by race and ethnicity.
"To our knowledge, this cohort study investigating calcium source and tumor site was the most extensive analysis to date on the association of calcium intake with incident CRC," the research team stated. They emphasized the importance of examining calcium-CRC associations across population subgroups traditionally identified as having lower calcium intake in the general US population.
Study Limitations and Future Directions
The researchers acknowledged several limitations in their analysis:
- Dietary information was collected only at baseline, preventing assessment of changes in calcium intake over time
- Limited statistical power for detailed stratified analyses by sex or race and ethnicity due to smaller case numbers in some subgroups
Despite these constraints, the findings suggest that increasing calcium intake, particularly among populations with lower baseline consumption, may help reduce disparities in colorectal cancer risk. The researchers emphasize the need for additional studies focusing on racial and ethnic minority populations to further validate these findings.
