Middle to older-aged adults who ate at least three servings of whole grains daily had smaller increases in waist size, BP, and blood sugar levels over time compared to those who ate less than one-half of serving per day, as per the findings of a new research.
Published in the Journal of Nutrition, the study by researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University 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.
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 results showed that for each four-year interval: Waist size increased by an average of over 1 inch in the low intake participants, versus about half an 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.
“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 Nicola McKeown, senior and corresponding author and a scientist on the Nutritional Epidemiology Team at the USDA HNRCA.
“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 fibre in whole grains can have a satiating effect, and magnesium, potassium, and antioxidants may contribute to lowering blood pressure. The soluble fibre, in particular, may have a beneficial effect on post-meal blood sugar spikes,” said Caleigh Sawicki. Sawicki did this work as part of her doctoral dissertation while a student at the Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy at Tufts University and while working with the Nutritional Epidemiology Team at the USDA HNRCA.
The greatest contributor to whole-grain intake among participants was whole-wheat bread and ready-to-eat whole-grain breakfast cereals. 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. Whole grains have a fibre-rich outer layer and an inner germ layer packed with B vitamins, antioxidants, and small amounts of healthy fats.
