Recommendation-based dietary indexes and risk of colorectal cancer in the Nurses' Health Study and Health Professionals Follow-up Study

Abstract

Background: Many dietary indexes exist for chronic disease prevention, but the optimal dietary pattern for colorectal cancer prevention is unknown.

Objective: We sought to determine associations between adherence to various dietary indexes and incident colorectal cancer in 2 prospective cohort studies.

Design: We followed 78,012 women in the Nurses' Health Study and 46,695 men in the Health Professionals Follow-up Study from 1986 and 1988, respectively, until 2012. We created dietary index scores for the Dietary Approaches to Stop Hypertension (DASH) diet, Alternative Mediterranean Diet (AMED), and Alternative Healthy Eating Index-2010 (AHEI-2010) and used Cox regression to estimate HRs and 95% CIs for risk of colorectal cancer (CRC) and by anatomic subsite. We also conducted latency analyses to examine associations between diet and CRC risk during different windows of exposure. We conducted analyses in men and women separately, and subsequently pooled these results in a random-effects meta-analysis.

Results: We documented 2690 colorectal cancer cases. Pooled multivariable HRs for colorectal cancer risk comparing the highest to lowest quintile of diet scores were 0.89 (95% CI: 0.74, 1.08; P-trend = 0.10) for DASH, 0.89 (95% CI: 0.73, 1.10; P-trend = 0.31) for AMED, and 0.95 (95% CI: 0.83, 1.09; P-trend = 0.56) for AHEI-2010 (P-heterogeneity ≥ 0.07 for all). In sex-specific analyses, we observed stronger associations in men for all dietary indexes (DASH: multivariable HR = 0.81, 95% CI: 0.66, 0.98; P-trend = 0.003; AMED: multivariable HR = 0.80, 95% CI: 0.65, 0.98; P-trend = 0.02; AHEI-2010: multivariable HR = 0.88, 95% CI: 0.72, 1.07; P-trend = 0.04) than in women (multivariable HRs range from 0.98 to 1.01).

Conclusions: Adherence to the DASH, AMED, and AHEI-2010 diets was inversely associated with colorectal cancer risk in men. These diets were not associated with colorectal cancer risk in women. This observational study was registered at http://www.clinicaltrials.gov as NCT03364582.

FIGURE 1

Multivariable HRs and 95% CIs for highest compared with lowest quintile of DASH, AMED, and AHEI-2010 scores and CRC risk by latency period in the NHS and HPFS separately and pooled. The circles and vertical lines correspond to multivariable HRs and 95% CIs, respectively, for those in the fifth quintile of the dietary index of interest compared with those in the first quintile of that dietary index with the given lag (n = 78,012 women in the NHS and n = 46,695 men in the HPFS). The HRs and 95% CIs were obtained from Cox regression analyses. The Pooled panel shows multivariable HRs and 95% CIs when men and women were pooled in a meta-analysis using a random effects model. All models were adjusted for total energy intake (kcal/d, quintiles), alcohol intake (g/d, quintiles), physical activity (MET-hours/wk, quintiles), NSAID use [≥2 NSAIDs/wk vs. <2 NSAIDs/wk (ref)], family history of CRC [yes vs. no (ref)], previous CRC screening via colonoscopy or sigmoidoscopy [yes vs. no (ref)], history of polyps [yes vs. no (ref)], smoking [never smoker (ref), 0–<10, 10–<20, 20–<30, 30–<40, 40–<50, ≥50 pack-years], multivitamin use [regular use vs. nonuse (ref)], supplemental calcium intake [none (ref), >0–200, >200–400, >400–600, >600 mg/d], and young adult BMI [in kg/m²; <25 (ref), 25–<27.5, 27.5–<30, ≥30]; in women, we additionally adjusted for menopausal status [postmenopausal vs. not (ref)] and postmenopausal hormone use [never use (ref), past use, current use]. AMED, Alternative Mediterranean Diet; AHEI-2010, Alternative Healthy Eating Index-2010; CRC, colorectal cancer; DASH, Dietary Approaches to Stop Hypertension; HPFS, Health Professionals Follow-Up Study; MET, metabolic task equivalent; NHS, Nurses' Health Study; NSAID, nonsteroidal anti-inflammatory drug.