Higher intake of whole grains associated with lower risk of major chronic diseases and death

Even small increases in consumption could bring substantial health benefits
June 13, 2016

Cereal plant, 7-grain bread, wholegrain food (credit: iStock)

A meta-analysis of 45 studies (64 publications) of consumption of whole grain by an international team of researchers, led by Dagfinn Aune, PhD, at Imperial College London, found lower risks of coronary heart disease and cardiovascular disease overall, as well as deaths from all causes and from specific diseases, including stroke, cancer, diabetes, infectious and respiratory diseases.

The researchers say these results “strongly support dietary recommendations to increase intake of whole grain foods in the general population to reduce risk of chronic diseases and premature mortality.”

The results have been published in an open-access paper in the British Medical Journal (BMJ).

The greatest benefit was seen for people who increased from no intake of whole grain to two servings per day, equivalent to 32 g/day, such as 32 g of whole grain wheat, or to 60 g product/day, such as 60 g of whole grain wheat bread.

Further reductions in risks were observed up to 7.5 servings a day, equivalent to 225 g/day of whole grain products, and suggest additional benefits at higher intakes.

Relation to specific types of disorders

A large body of evidence has emerged on the health benefits of whole grain foods over the last 10–15 years. Grains are one of the major staple foods worldwide and provide on average 56% of energy intake and 50% of protein intake.

But recommendations on the daily amount and types of whole grain foods needed to reduce risk of chronic disease and mortality have often been unclear or inconsistent. So the researchers carried out a systematic review and meta-analysis of 45 published studies on whole grain consumption in relation to several health outcomes and all-cause mortality.*

They found reductions in the relative risk of coronary heart disease (19%), cardiovascular disease (22%), all cause mortality (17%), and mortality from stroke (14%), cancer (15%), respiratory disease (22%), infectious disease (26%), and diabetes (51%) per 90 g/day of whole grain product (one serving equals 30g of whole grain product).

Reductions in risks of cardiovascular disease and all-cause mortality were associated with intake of whole grain bread, whole grain breakfast cereals, and added bran, as well as total intake of bread and breakfast cereals.

There was little evidence of an association with intake of refined grains, white rice, total rice or other grains.

Caveats and recommendations

Few people may have total grain intake of three or more servings a day, so the authors recommend “increasing intake of whole grains, and as much as possible to choose whole grains rather than refined grains.”

However, the researchers noted that systematic reviews and meta-analyses involving observational research cannot be used to draw conclusions about cause and effect.

They call for more research to determine health benefits of different types of whole grain in different geographical regions, as most of the current evidence is from the U.S. and fewer studies have been conducted in Europe, Asia and other regions. Studies of specific diseases, and less common causes of deaths, are needed.

They caution that it’s important that “great care” should be taken not to promote whole grain foods with high sugar and salt content, and call for more research on the “biological mechanisms of health effects and contribution to health of different grain types.”

A related study published in The Journals of Gerontology, Series A (recently described on KurzweilAI — see Dietary fiber has biggest influence on successful aging, research reveals) found that fiber that made the biggest difference to what the researchers termed “successful aging,” meaning “the absence of disability, depressive symptoms, cognitive impairment, respiratory symptoms, and chronic diseases including cancer, coronary artery disease, and stroke.”

* They included more than 7,000 cases of coronary heart disease, 2,000 cases of stroke, 26,000 cases of cardiovascular disease, 34,000 deaths from cancer, and 100,000 deaths among 700,000 participants.

Abstract of Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies

Objective To quantify the dose-response relation between consumption of whole grain and specific types of grains and the risk of cardiovascular disease, total cancer, and all cause and cause specific mortality.

Data sources PubMed and Embase searched up to 3 April 2016.

Study selection Prospective studies reporting adjusted relative risk estimates for the association between intake of whole grains or specific types of grains and cardiovascular disease, total cancer, all cause or cause specific mortality.

Data synthesis Summary relative risks and 95% confidence intervals calculated with a random effects model.

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.

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.