Introduction: Whole grain intake has been associated with lower risks of multiple chronic conditions, but its association with mortality warrants further evaluation.
Hypothesis: We performed a meta-analysis of prospective cohort studies on the association of whole grain intake with all-cause and cause-specific mortality, and tested the hypothesis that they followed inverse dose-response pattern.
Methods: Published studies reporting relative risks (RRs) between whole grain consumption and mortality from Medline and Embase through August, 2015. Original results from National Health and Nutrition Examination Survey (NHANES) III and NHANES 1999-2004 were included. Whole grain ingredients (gram/day) were estimated among studies reporting RRs for ≥3 categories of whole grain intake.
Results: Fourteen unique analyses were included, which consisted of 786,076 participants, 97,867 all-cause deaths, 23,957 CVD deaths, and 37,492 cancer deaths. Pooled RRs (95% confidence intervals) comparing high with low whole grain categories were 0.84 (0.80, 0.88; P <0.001, I2=74%, P heterogeneity<0.001) for all-cause mortality, 0.82 (0.79, 0.85; P <0.001, I2=0%, P heterogeneity=0.53) for CVD mortality, and 0.88(0.83, 0.94; P <0.001, I2=54%, P heterogeneity=0.02) for cancer mortality. Whole grain consumption was <50 grams/day among most studies. Dose-response meta-analysis showed strong monotonic associations between whole grain and mortality (All P nonlinearity > 0.05): RRs (95%CIs) for each 16 grams/day increase (approximately 1 serving/day) in whole grain were 0.93(0.92, 0.94) for all-cause mortality, 0.91(0.90, 0.93) for CVD mortality, and 0.95(0.94, 0.96) for cancer mortality. These findings were robust in several stratified analyses and/or sensitivity analyses. Egger’s test did not suggest significant publication bias.
Conclusions: Our findings supported health benefit of increasing current whole grain intake of <1 serving/day to ≥3 servings/day as recommended by current Dietary Guidelines for Americans.