Nutritional Pearl: Cut Your Risk of Heart Disease with Whole Grains

John is a 52-year-old overweight man with high blood pressure. He tells you that a significant proportion of his diet consists of pasta and bread, and asks if you think switching from refined grain to whole grain options could help his blood pressure levels.

How do you advise your patient?
(Answer and discussion on next page)

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Answer: Switching to whole grains could help to lower blood pressure levels.

Whole grains are 1 of the 9 principles of the Mediterranean Diet, and they're powerful stuff. Not only are they more satisfying due to their higher fiber content, but we've seen that diets rich in whole grains can help people lose more abdominal fat, help older folks reduce their overall risk of metabolic syndrome, improve people's insulin response (without weight loss), and help them avoid heart disease as well as type 2 diabetes.

The Research

Many of those previous studies were cross-sectional, longitudinal, or involved providing whole grain foods to be added to the participants' usual diets—all of which can mean multiple possible confounders. In a very rigorous study, authors affiliated with the Cleveland Clinic decided to provide the entirety of their participants' diets (both food and drink) in a crossover study designed to assess the impact of whole grains on weight and body fat, blood pressures, cholesterol scores, and insulin scores.
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Thirty-three overweight or obese men and women of at least 50 years of age with no history of heart disease participated in the study. For the first 8 weeks, half of the participants were provided a balanced diet designed to maintain their body weight while including mostly refined grains, while the other half of the participants were provided a similarly balanced and body-weight-maintaining diet that included mostly whole grains.

After the initial 8 weeks the participants returned to their usual diets for 10 weeks for a washout period, then the 2 groups switched their prescribed diets for an additional 8 weeks.

At the start and end of each test diet period, the authors recorded the participants' weight and tested their blood pressures along with other blood tests, including cholesterol and glucose scores.

The Results

It's interesting that despite their isocaloric diets, both groups lost about the same amount of weight and fat mass during the 2 testing periods of the study while also improving their total and LDL cholesterol scores. The big difference in results between the 2 diet periods, however, was in diastolic blood pressures: the refined grains diet reduced DBP by about 1% while the whole grains diet reduced DBP by about 8%—about a 10% improvement in overall blood pressures.

What this means for you

We physicians don't talk with our patients much about diastolic blood pressures specifically, but we're well aware that every 10-point increase in diastolic blood pressure doubles our patients' risk of death from heart disease or stroke. Your patients can help keep their pressures in the normal range by reducing their dietary sodium intake and switching to whole grains rather than refined grains.

Reference:

Kirwan JP, Malin SK, Scelsi AR, et al. A whole-grain diet reduces cardiovascular risk factors in overweight and obese adults: a randomized controlled trial J Nutr 2016;146(11):2244-51.