Eating more whole grains may decrease people’s risk of death by up to 15%—particularly the risk from heart disease, according to a large new long-term study from Harvard School of Public Health (HSPH).

The study also found that bran, a component of whole grain foods, was associated with similar beneficial effects. Bran intake was linked with up to 6% lower overall death risk and up to 20% lower cardiovascular disease (CVD)-related risk.

The study appears online January 5, 2015 in JAMA Internal Medicine.

“This study further endorses the current dietary guidelines that promote whole grains as one of the major healthful foods for prevention of major chronic diseases,” said Qi Sun, assistant professor in the Department of Nutrition at HSPH and senior author of the study.

Eating More Whole Grains Helps Reduce Risk of Disease

Although eating more whole grains has been previously associated with a lower risk of major chronic diseases, such as type 2 diabetes and CVD, until now there had been limited evidence regarding whole grains’ link with mortality.

HSPH researchers and colleagues looked at data from more than 74,000 women from the Nurses’ Health Study and more than 43,000 men from the Health Professionals Follow-Up Study who filled out questionnaires about their diet every two or four years from the mid-1980s to 2010. Adjusting for a variety of factors, such as age, smoking, body mass index, physical activity, and overall diet excluding whole grains, the researchers compared the participants’ whole grain intake with mortality data over an approximately 25-year period.

They found that whole grain intake was associated with up to 9% decreased risk of overall mortality and up to 15% decreased risk of CVD-related mortality. For each serving of whole grains (28g/day), the overall death risk dropped by 5%, and by 9% for CVD-related death.

In contrast, the researchers found no association between eating whole grains and lowered cancer-related mortality risk. They also didn’t find any decreased risk from eating germ, another essential component of whole grains.

Replacing refined grains and red meats with whole grains is also likely to lower mortality risk, according to the study. Swapping just one serving of refined grains or red meat per day with one serving of whole grains was linked with lower CVD-related mortality risk: 8% lowered risk for swapping out refined grains and 20% lowered risk for swapping out red meat.