In a new study from Tufts University, researchers found middle- to older-aged adults who ate at least three servings of whole grains daily had smaller increases in waist size, blood pressure, and blood sugar levels over time.
In the study, the team examined how whole- and refined-grain intake over time impacted five risk factors of heart disease: Waist size, blood pressure, blood sugar, triglyceride, and HDL (‘good’) cholesterol.
Using data from the Framingham Heart Study Offspring Cohort, which began in the 1970s to assess long-term risk factors of heart disease, the new research examined health outcomes associated with whole- and refined-grain consumption over a median of 18 years.
The 3,100 participants from the cohort were mostly white and, on average, in their mid-50s at the start of data collection.
The team compared changes in the five risk factors, over four-year intervals, across four categories of reported whole grain intake, ranging from less than a half serving per day to three or more servings per day.
According to the Dietary Guidelines for Americans 2020-2025, the recommended amount of whole grains is three or more servings daily.
An example of a serving is one slice of whole-grain bread, a half cup of rolled oats cereal, or a half-cup of brown rice.
The team showed that for each four-year interval, waist size increased by an average of over 1 inch in the low intake participants, versus about ½ inch in the high intake participants.
Even after accounting for changes in waist size, average increases in blood sugar levels and systolic blood pressure were greater in low intake participants compared to high intake participants.
The researchers also studied the five risk factors across four categories of refined-grain intake, ranging from less than two servings per day to more than four servings per day.
Lower refined-grain intake led to a lower average increase in waist size and a greater mean decline in triglyceride levels for each four-year period.
These findings suggest that eating whole-grain foods as part of a healthy diet delivers health benefits beyond just helping us lose or maintain weight as we age.
In fact, they suggest that people who eat more whole grains are better able to maintain their blood sugar and blood pressure over time. Managing these risk factors as we age may help to protect against heart disease.
The team says there are several reasons that whole grains may work to help people maintain waist size and reduce increases in the other risk factors.
The presence of dietary fiber in whole grains can have a satiating effect, and magnesium, potassium, and antioxidants may contribute to lowering blood pressure.
The soluble fiber in particular may have a beneficial effect on post-meal blood sugar spikes.
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The study is published in the Journal of Nutrition. One author of the study is Nicola McKeown.
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