Whole grain intake is related to a clear dose-dependent reduction in the risk for coronary heart disease, stroke, cardiovascular disease, total cancer deaths, and all-cause mortality, the authors of a new meta-analysis report. They observed a similar relationship between whole grains and the risk for respiratory disease, diabetes, infectious disease, and deaths not related to cardiovascular disease or cancer.
Conclusions This meta-analysis provides further evidence that whole grain intake is associated with a reduced risk of coronary heart disease, cardiovascular disease, and total cancer, and mortality from all causes, respiratory diseases, infectious diseases, diabetes, and all non-cardiovascular, non-cancer causes. These findings support dietary guidelines that recommend increased intake of whole grain to reduce the risk of chronic diseases and premature mortality.
Results 45 studies (64 publications) were included. The summary relative risks per 90 g/day increase in whole grain intake (90 g is equivalent to three servings—for example, two slices of bread and one bowl of cereal or one and a half pieces of pita bread made from whole grains) was 0.81 (95% confidence interval 0.75 to 0.87; I2=9%, n=7 studies) for coronary heart disease, 0.88 (0.75 to 1.03; I2=56%, n=6) for stroke, and 0.78 (0.73 to 0.85; I2=40%, n=10) for cardiovascular disease, with similar results when studies were stratified by whether the outcome was incidence or mortality. The relative risks for morality were 0.85 (0.80 to 0.91; I2=37%, n=6) for total cancer, 0.83 (0.77 to 0.90; I2=83%, n=11) for all causes, 0.78 (0.70 to 0.87; I2=0%, n=4) for respiratory disease, 0.49 (0.23 to 1.05; I2=85%, n=4) for diabetes, 0.74 (0.56 to 0.96; I2=0%, n=3) for infectious diseases, 1.15 (0.66 to 2.02; I2=79%, n=2) for diseases of the nervous system disease, and 0.78 (0.75 to 0.82; I2=0%, n=5) for all non-cardiovascular, non-cancer causes. Reductions in risk were observed up to an intake of 210-225 g/day (seven to seven and a half servings per day) for most of the outcomes. Intakes of specific types of whole grains including whole grain bread, whole grain breakfast cereals, and added bran, as well as total bread and total breakfast cereals were also associated with reduced risks of cardiovascular disease and/or all cause mortality, but there was little evidence of an association with refined grains, white rice, total rice, or total grains.
The authors defined one serving of all grains or whole or refined grains as 30 g, equivalent to one slice of bread or one serving of breakfast cereal. The researchers defined a serving of pasta as 150 g, and a serving of white or brown rice as 167.25 g. They studied changes in the risk for illness or mortality per 90-g increase in whole grain intake and between the lowest and highest intakes, up to 210 to 225 g (7 – 7.5 servings) per day. The summary relative risk for coronary heart disease for high vs low whole grain consumption was 0.79 (P heterogeneity = 0.63; n = 7 studies), equivalent to a risk reduction of 21%. For stroke, the pooled relative risk for high vs low intake was 0.87 (P heterogeneity = .21; n = 6 studies), a risk reduction of 13%. High vs low whole grain intake also was associated with a 16% reduction in the risk for cardiovascular disease (summary relative risk, 0.84; P heterogeneity = .48; n = 10 studies). In a similar comparison for total cancer, the summary relative risk was 0.89 (P heterogeneity = .003; n = 6 studies), and for all-cause mortality, the pooled relative risk was 0.82 (P heterogeneity < 0.001; n = 11 studies), translating into risk reductions of 11% and 18%, respectively.
In the dose–response analyses, the summary relative risk for coronary heart disease per 90 g/day was 0.81 (n = 7 studies), or a 19% reduction in risk. The summary relative risk for stroke per 90 g/day was 0.88 (n = 6), equivalent to a 12% risk reduction. For cardiovascular disease, the summary relative risk was 0.78 (n = 10) or a 22% risk reduction per 90 g/day. Total cancer was associated with a summary relative risk per 90 g/day of 0.85 (P heterogeneity = .16), a 15% reduction in risk. The summary relative risk for all-cause mortality per 90 g/day was 0.83 (P heterogeneity < .001), a reduction of 17%.
The authors also observed reductions of 19%, 36%, 20%, and 21%, respectively, in the relative risk for mortality from respiratory disease, diabetes, infectious disease, and all deaths not related to cancer or cardiovascular disease between high and low intakes of whole grains. Most of the studies showed “a clear dose-response relation with further reductions with intakes up to seven to seven and a half servings a day (210-225 g/day),” the authors write. These findings suggest that “even moderate increases in whole grain intake could reduce the risk of premature mortality.”
Take great care not to promote whole grain foods with high sugar and salt content.
The findings support dietary recommendations to increase intake of whole grains and as much as possible to choose whole grains rather than refined grains.