According to new research, middle-aged to older persons who consumed at least three servings of whole grains per day had smaller increases in waist size, blood pressure, and blood sugar levels over time than those who consumed less than one-half of a serving per day.
Researchers at Tufts University’s Jean Mayer USDA Human Nutrition Research Center on Aging have examined how whole-grain and refined-grain intake over time impacted five risk factors of heart disease such as Waist size, blood pressure, blood sugar, triglyceride, and HDL (“good”) cholesterol.
Furthermore, 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 research 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.
According to the Dietary Guidelines for Americans 2020-2025, three or more servings of whole grains per day are recommended. 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.
In the low intake group, waist size increased by almost an inch on average, compared to around half an inch in the high intake group. Even after accounting for changes in waist size, average increases in blood sugar levels and systolic blood pressure were greater in low intake participants while compared to high intake participants.
“Our 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, these data 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,” said Dr. Nicola McKeown, senior and corresponding author and a scientist on the Nutritional Epidemiology Team at the USDA HNRCA.
Whole-wheat bread and ready-to-eat whole-grain breakfast cereals were the most important sources of whole grains for participants. The refined grains came mostly from pasta and white bread. The difference in health benefits between whole and refined grains may stem from the fact that whole grains are less processed than refined grains.
The outer layer of whole grains is high in fiber, while the inner germ layer is high in B vitamins, antioxidants, and small levels of healthy fats. Milling whole grains removes these nutrient-dense components, leaving only the starch-packed refined grain behind.