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

Introduction

- Whole grains (WGs) are rich in dietary fiber, vitamins, minerals, phytochemicals, and other bioactive compounds that may jointly favor long-term health.

- This meta-analysis estimated WG ingredient intake in dry weight among eligible studies and explored potential dose-response relationships between WG intake and mortality.

Method

- Database: Medline, Embase, and clinicaltrials.gov, and unpublished results from National Health and Nutrition Examination Survey (NHANES) III and NHANES 1999 to 2004.

 - Search period: until Feb 2015

- Language:  No restriction

- Eligibility criteria: Prospective cohort design, the exposure included intakes of WG ingredients (with specified methods for calculation) or WG foods (with specified food items); and the outcome included mortality from all causes, CVD, or cancer.

Results

- Number of Studies included: 14; with 786,076 participants. Among the participants, there were 97,867 (12.45%) total death, 23,957 (3.05%) CVD death and 37,492 (4.77%) Cancer death.

- Locations of included studies: US (n=10), Scandinavian countries (n=3), UK (n=1)

- Publication bias: No

WG intake (high vs low):

-Total mortality: RR 0.84 (95% CI, 0.80-0.88; p<0.001); I²=74%; p<0.001

-CVD mortality: RR 0.82 (95% CI, 0.79-0.85; p<0.001); I²=0%; p=0.53

-Cancer mortality: RR 0.88 (95% CI, 0.83-0.94; p<0.001); I²=54%; p=0.02

For each 16-g/day increase in WG (approximately 1 serving/day), relative risk for:

- Total mortality: 0.93 (95% CI 0.92-0.94; p<0.001)

- CVD mortality: 0.91 (95% CI, 0.90-0.93; p<0.001)

- Cancer mortality: 0.95 (95% CI, 0.94-0.96; p<0.001)

- Heterogeneities were not explained by study location, WG assessments, dietary questionnaires, study aim, sample size, median follow-up duration, and adjustment for dietary factors, study quality or ages at baseline. Meta-regression unable to identify source of heterogeneity.

- Publication bias: Not detected

Conclusion:

This finding support that dietary recommendation of at least 3 servings per days of WG intake.

Zong et al. Circulation. 2016;133:2370-2380. DOI: 10.1161/CIRCULATIONAHA.115.021101.

Note:

RR: relative risk, CI: confidence interval, I²: heterogeneity

In this meta-analysis, RR<1 indicates protective effect (lower mortality).

Heterogeneity (as indicated by I²>50% or p for I²<0.05) may weaken the findings of a meta-analysis