Whole grains form a part of many diets deemed to be beneficial for health – such as the Mediterranean diet. But what health benefits do whole grains offer in their own right? According to a new study, eating more of them may reduce mortality, particularly deaths resulting from cardiovascular disease.
Grains are made up of three parts: the bran layers, germ and endosperm. Refined grains often have the bran layers and germ removed, while whole grains contain all three elements. Foods that contain whole grains include whole-wheat flour, oatmeal, cornmeal, bulgur and brown rice.
In general, whole grains are thought to be better for health than refined grains. As part of a healthy diet, whole grains have been associated with reduced blood cholesterol and improved weight maintenance.
“Compared with refined carbohydrates, whole grains contain many beneficial nutrients and phytochemicals that primarily reside in the outer layers of grains that are removed during milling processes to produce refined grain products,” explain the researchers, including Hongyu Wu, PhD, of the Harvard School of Public Health in Boston, MA.
However, the team says data from studies investigating the association between whole grain intake and overall health have been “inconsistent.” As such, they set out to assess the effect of whole grain intake on risk of death.
To reach their findings – published in JAMA Internal Medicine – Wu and colleagues analyzed data from two large studies: the Nurses’ Health Study, from which 74,341 women were assessed between 1984 and 2010, and the Health Professionals Follow-Up Study, from which 43,744 men were analyzed between 1986 and 2010.
Every 2-4 years, participants were required to complete food frequency questionnaires, from which whole grain intakes were estimated based on the dry weight of whole grain ingredients in all grain-containing foods consumed, such as bread, rice, breakfast cereals and pasta.
The researchers note that at the baseline of both studies, all participants were free of cancer and cardiovascular disease (CVD). Over both studies, the team identified 26,920 deaths.
The results of the analysis revealed that a higher intake of whole grains was associated with reduced risk of overall mortality and lower risk of CVD mortality; each serving of whole grains (28 g) was linked to a 5% reduced total mortality risk or a 9% lower risk of CVD mortality.
Wu and colleagues note, however, that no association between whole grain intake and reduced cancer mortality was found.
These findings remained even after accounting for factors that may influence mortality, such as smoking, age, body mass index (BMI) and physical activity.
Commenting on their results, the researchers say:
“These findings further support current dietary guidelines that recommend increasing whole grain consumption to facilitate primary and secondary prevention of chronic diseases and also provide promising evidence that suggests a diet enriched with whole grains may confer benefits toward extended life expectancy.”
The team points out that the study is subject to some limitations. They note that measurement errors in whole grain intake and other factors among participants are “inevitable” and may have influenced the results, despite the food frequency questionnaires used having been validated against diet records previously.
In addition, the researchers point out that study participants were mostly middle-aged or older and of European ancestry, which raises the question as to whether the results could be generalizable to other populations.
Although no link was found between whole grain intake and cancer mortality in this study, a 2011 study reported by Medical News Today claimed a diet rich in whole grains and fiber could reduce the risk of colorectal cancer.