Calcium Intake and Risk of Colorectal Cancer in the NIH-AARP Diet and Health Study.

Importance: Calcium intake is associated with a reduced risk of colorectal cancer (CRC), although it remains unclear whether this association varies by calcium source or tumor site. Moreover, there are disparities in calcium intake by race and ethnicity, but the impact of low calcium consumption on CRC risk in specific racial and ethnic populations is unclear. Objective: To investigate the association between calcium intake and CRC risk, considering the source of calcium and tumor site and across racial and ethnic groups. Design, Setting, and Participants: This cohort study analyzed data from the National Institutes of Health-AARP Diet and Health Study. Participants were aged 50 to 71 years at baseline (October 1995 to May 1996), had self-reported good health and neither extremely high nor low caloric or calcium intake, and were followed up until the date of their first primary cancer diagnosis, death, loss to follow-up, or end of follow-up (December 31, 2018). Data were analyzed from April 2022 to April 2024. Exposure: Calcium intake was estimated from dietary sources (dairy and nondairy), supplements, and total intake. Main Outcomes and Measures: The primary outcome was CRC incidence. Multivariable-adjusted Cox proportional hazards regression models estimated hazard ratios (HRs) and 95% CIs using the lowest sex-specific quintile of calcium intake as the reference. Results: Among 471 396 participants who were cancer-free at baseline, mean (SD) baseline age was 62.0 (5.4) years and 59.5% were male. During 7 339 055 person-years of follow-up (median, 18.4 years [IQR, 9.2-22.5 years]), 10 618 first primary CRC cases were identified. Mean (SD) total calcium intake for the lowest quintile (Q1) was 401 mg/d (104 mg/d) for females and 407 mg/d (95 mg/d) for males and for the highest quintile (Q5) was 2056 mg/d (412 mg/d) for females and 1773 mg/d (444 mg/d) for males. Dairy, nondairy, and supplemental sources contributed a mean (SD) of 42.1% (43.5%), 34.2% (24.5%), and 23.7% (38.3%) of total calcium intake, respectively. Higher total calcium intake (Q5 vs Q1) was associated with a lower risk of CRC (hazard ratio [HR], 0.71; 95% CI, 0.65-0.78; P < .001 for trend), with consistent results across calcium sources and tumor sites. Among non-Hispanic Black participants, the mean (SD) calcium intake was 382 mg/d (108 mg/d) for Q1 and 1916 mg/d (466 mg/d) for Q5, with no association of total calcium intake with CRC risk (Q5 vs Q1: HR, 0.60; 95% CI, 0.32-1.13; P = .12 for trend); there was no evidence of effect measure differences by race and ethnicity. Conclusions and Relevance: In this cohort study, higher calcium intake was consistently associated with reduced CRC risk across tumor sites and sources of calcium. Increasing calcium intake, especially among groups with lower consumption, may be associated with reductions in avoidable differences in CRC risk.