Whole Grain Intake and All, CVD, and Cancer Mortality
Is whole grain consumption inversely associated with mortality risk?
This was a meta-analysis of trials that reported whole grain intake and mortality. Prospective cohort studies were identified using Medline, Embase, and clinicaltrials.gov; publications through February 2016 were included. Unpublished results from National Health and Nutrition Examination Survey (NHANES) III and NHANES 1999-2004 were also included. Inclusion criteria were prospective study design with whole grains as an exposure and mortality as an outcome. Studies with the longest duration of follow-up from one cohort were selected to represent the cohort. The primary outcomes of interest were all-cause mortality, cardiovascular disease (CVD) mortality, and cancer mortality. A total of 4,062 publications were identified, of which 3,966 were excluded upon review of the title and abstract, and 84 publications were excluded after a full text review. An additional five were excluded as multiple reports of the same population. A total of three publications were excluded, as the participants had existing CVD or cancer at baseline, and four publications were excluded for missing information on whole grains.
A total of 14 studies, with 786,076 participants, were included in this meta-analysis; 97,867 total deaths, 23,957 CVD deaths, and 37,492 cancer deaths were reported. Pooled relative risks comparing extreme whole grain categories (high vs. low) were 0.84 (95% confidence interval [CI], 0.80-0.88; p < 0.001; I2 = 74%; p heterogeneity < 0.001) for total mortality, 0.82 (95% CI, 0.79-0.85; p < 0.001; I2 = 0%; p heterogeneity = 0.53) for CVD mortality, and 0.88 (95% CI, 0.83-0.94; p < 0.001; I2 = 54%; p heterogeneity = 0.02) for cancer mortality. Intakes of whole grain ingredients in dry weight were estimated among studies reporting relative risks for ≥3 quantitative whole grain categories, and they were <50 g/d among most study populations. The two-stage dose response random-effects meta-analysis showed monotonic associations between whole grain intake and mortality (p nonlinearity > 0.05). For each 16-g/d increase in whole grain (approximately 1 serving per day), 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.
The investigators concluded that this meta-analysis demonstrated inverse associations of whole grain intake with total and cause-specific mortality. This association was particularly strong and robust for CVD mortality. The authors state that these findings support current Dietary Guidelines for Americans, which recommends at least three servings per day of whole grain intake.
These data support the advice for intake of healthy whole grains consistent with a balanced diet.
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