Whole Grain Intake and Mortality From All Causes, Cardiovascular Disease, and Cancer: A Meta-Analysis of Prospective Cohort Studies

Background: Current findings on associations between whole grain (WG) intake and mortality are inconsistent and have not been summarized by meta-analysis.

Methods and results: We searched for prospective cohort studies reporting associations between WG intake and mortality from all causes, cardiovascular disease (CVD), and cancer through February 2016 in Medline, Embase, and clinicaltrials.gov, and we further included unpublished results from National Health and Nutrition Examination Survey (NHANES) III and NHANES 1999 to 2004. Fourteen studies were eligible for analysis, which included 786 076 participants, 97 867 total deaths, 23 957 CVD deaths, and 37 492 cancer deaths. Pooled relative risks comparing extreme WG categories (high versus low) were 0.84 (95% confidence interval [CI], 0.80-0.88; P<0.001; I(2)=74%; Pheterogeneity<0.001) for total mortality, 0.82 (95% CI, 0.79-0.85; P<0.001; I(2)=0%; Pheterogeneity=0.53) for CVD mortality, and 0.88 (95% CI, 0.83-0.94; P<0.001; I(2)=54%; Pheterogeneity=0.02) for cancer mortality. Intakes of WG ingredients in dry weight were estimated among studies reporting relative risks for ≥3 quantitative WG categories, and they were <50 g/d among most study populations. The 2-stage dose-response random-effects meta-analysis showed monotonic associations between WG intake and mortality (Pnonlinearity>0.05). For each 16-g/d increase in WG (≈1 serving per d), relative risks of total, CVD, and cancer mortality were 0.93 (95% CI, 0.92-0.94; P<0.001), 0.91 (95% CI, 0.90-0.93; P<0.001), and 0.95 (95% CI, 0.94-0.96; P<0.001), respectively.

Conclusions: Our meta-analysis demonstrated inverse associations of WG intake with total and cause-specific mortality, and findings were particularly strong and robust for CVD mortality. These findings further support current Dietary Guidelines for Americans, which recommends at least 3 servings per day of WG intake.