Nutrition professionals have long recommended that we include substantial amounts of whole-grain foods in our diets.
An example is the 2015 Dietary Guidelines for Americans, which suggests that we make “half our grains whole grains.”
But Americans (and many others around the world) prefer refined grains when it comes to the breads, pastas, breakfast cereals, pastries, and rice they eat on a daily basis.
New evidence suggests however that we reconsider our choices in this regard.
In this study, a research team headed up by Dr. John Kirwan (the Lerner Research Institute and Cleveland Clinic) examined what happens to biomarkers of cardiovascular health when overweight and obese adults alternate their consumption of refined and whole-grain products.
This research is important because heart disease and stroke constitute today’s leading causes of death in the United States, and continuing upward obesity trends suggest this problem is not going away in the near future.
To test their hypothesis that whole-grain foods are more heart-healthy than their refined-grain counterparts, the researchers recruited 33 willing participants (mostly women) for their 26-week-long study.
During the first 8 weeks, half of the recruits were provided with meals and snacks prepared with whole-grain wheat or rice. The other half consumed similar meals made with refined wheat or rice.
This intervention period was followed by a 10-week “wash-out” period during which the participants prepared their own foods to their own liking.
After the wash-out period, each participant was provided for 8 weeks with the dietary treatment they didn’t receive in the first intervention period.
The whole-grain and refined-grain meal plans were designed to provide similar calories and major nutrients, so that any differential effects could be attributed directly to the type of grain consumed.
The researchers found that, compared to the refined-grain intervention period, consumption of whole-grain foods reduced diastolic blood pressure, which is the pressure our blood vessels experience between heartbeats.
In addition, adiponectin (a hormone produced by fat cells and thought to help protect against systemic inflammation) was higher when whole grains were eaten.
This was particularly surprising because both dietary interventions resulted in similar weight and body fat loss.
The researchers concluded that, because high diastolic blood pressure is a risk factor for early death in adults under 50 years of age, increased whole-grain food intake may provide a useful approach to control hypertension and stave off cardiovascular disease.