Whole Grain Consumption Linked to Less CVD and Lower Mortality, Meta-analyses Say
Two new meta-analyses add substantial support to the idea that increasing whole grain consumption can reduce the likelihood of dying from cardiovascular disease, with one showing that eating several servings of whole grains every day also can reduce mortality stemming from conditions as various as respiratory ailments, stroke, and infectious disease.
Health benefits from whole grains have been well documented, but dietary recommendations remain vague, experts say. There is a lack concrete evidence on the magnitude of benefit and how it might apply in different disease settings.
According to Dagfinn Aune (Imperial College London, England), lead author of one of the studies, his meta-analysis both provides firmer numbers for official dietary guidelines and highlights the impact healthy eating can have on overall and heart health.
“The most surprising finding was that there was a significant inverse association between whole grain intake and so many different causes of death,” he said in an email to TCTMD. “This suggest that the benefits of a high whole grain intake extends far beyond the previously established benefits for cardiovascular disease and provides the strongest evidence to date for a range of health benefits of eating more whole grains.”
Qi Sun, MD (Brigham and Women’s Hospital, Boston, MA), senior author of the other meta-analysis, told TCTMD that the key take away was the types of diseases seeing risk reductions.
Cardiovascular disease, diabetes, and cancer are “among the primary causes of death in the population, so you know it’s not surprising at all that whole grains consumption can also further reduce mortality and make people live a little bit longer,” he said.
Consolidating the Evidence on Whole Grains
Along with lead author Geng Zong, PhD (Brigham and Women’s Hospital), Sun and colleagues analyzed 14 studies published between 1970 and February 2015 plus unpublished data from the National Health and Nutrition Examination Survey gathered between 1999 and 2004. In all, the combined cohort included a total of 786,076 participants and 97,867 deaths. Median follow-up ranged from 6 to 28 years. Their results were published this week in Circulation.
The researchers found that individuals who ate at least 50 grams of dry whole grains a day (about three servings) had a 22% reduction in cardiovascular disease mortality and 15% reduction in cancer mortality. This same group also saw a 20% reduction in total mortality.
There was a dose-response relationship observed, with a greater protective effect seen at 50 or 70 grams per day than at 10 or 30 grams per day.
The second meta-analysis, published in BMJ this week, collected 45 studies from 1947 to 2016, for a total of 700,000 participants and 100,000 deaths. Aune and colleagues report that increasing consumption up to 90 grams per day of fresh whole grains (not dry) reduced risks of developing coronary heart disease (RR 0.84; 95% CI 0.77-0.92) and cardiovascular disease (RR 0.87; 95% CI 0.78-0.97).
In addition, the likelihood of dying from either of those conditions or from respiratory disease, stroke, infectious disease, or cancer were reduced. There also was a trend toward less diabetes-associated mortality.
Notably, these risk reductions were observed in a dose-response analysis all the way up to 225 grams per day.
“The results suggest that whole grains provide benefits for a range of organ systems and conditions and that we really should try to replace refined grains as much as possible with whole grains,” Aune told TCTMD.
Whole Grains the Magic Bullet?
Kim Williams, MD (Rush University Medical Center, Chicago), former president of American College of Cardiology and outspoken advocate of nutrition for cardiovascular disease prevention commented on Circulation paper for TCTMD. His hunch, he said, is that whole grains may be a marker for better eating over all, and that they might only be part of the solution for reducing risk.
“What hits me when people are eating more servings of grains [is] it’s probably a substitution effect that’s two-fold,” said Williams, who wasn’t involved in either study. “One is grains have properties such as vegetable proteins that lower blood pressure [and] plant sterols that lower cholesterol, and then on top of that when people are filling up with grains they are eating less animal products.”
Because similar effects have been found in increased consumption of nuts, Williams noted, it is likely that whole grains are simply one aspect of an overall pattern of better eating to improve health and prevent disease. The theory, he said, is that the more healthy food a person consumes, the less unhealthy food they will eat.
Yet Aune noted to TCTMD that “even studies that adjusted for intake of red meat and sugar-sweetened soft drinks found a reduced risk of mortality, suggesting that the observed effects are not simply replacement effects or due to confounding with these foods and drinks.”
A Time for Dietary Changes
Many countries employ vague language and unambitious serving sizes when recommending grain consumption, Cecilie Kyrø, PhD, and Anne Tjønneland, MD, PhD (Danish Cancer Society Research Center, Copenhagen, Denmark), write in an editorial accompanying the BMJ paper. Another concern is getting people to follow the official advice. Fewer than 6 percent of people eat the recommended servings in Denmark, a country with one of the highest whole grain intakes in the world, they point out.
According to the editorialists, the Aune meta-analysis is a welcome source of data for doctors who want to employ evidence-based medicine when working with individual patients to improve their diets.
As Williams lamented to TCTMD, most physicians don’t get nutrition education as part of their training. “And a lot of the nutrition education is based on improving diabetes and improving weight, and not so much focused on heart disease and stroke,” he said, adding “One can have a dramatic improvement if you get the data to physicians, and they change themselves and then try to change their patients.”
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Zong G, Gao A, Hu FB, Sun Q. Whole grain intake and mortality from all causes, cardiovascular disease, and cancer: a meta-analysis of prospective cohort studies. Circulation. 2016;133:2370-2380.
Aune D, Keum N, Giovannucci E, et al. 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. BMJ. 2016;353:i2716.
Kyrø C, Tjønneland A. Whole grains and public health: small increases in population intake could bring substantial benefits. BMJ. 2016;353:i3046.
- The authors and editorialists report having no relevant conflicts of interest.