Middle- to older adults who ate at least three servings of whole grains per day had less increase in waist size, blood pressure and blood sugar levels over time than those who ate less than one and a half servings per day, according to new research.
Published on July 13, 2021 Journal of NutritionThe study by Tufts University researchers at the Gene Mayer USDA Human Nutrition Research Center on Aging examined how whole- and refined-grain intake over time affects five risk factors for heart disease: waist size, blood pressure, blood sugar, triglycerides and HDL (“good “) cholesterol.
Using data from the Framingham Heart Study Offspring cohort, which began in the 1970s to assess long-term risk factors for heart disease, the new study examined health outcomes associated with whole- and refined-grain consumption over a median of 18 years. The cohort’s 3,100 participants were mostly white and, on average, in their mid-50s at the start of data collection.
The research team compared changes in five risk factors over a four-year period, in four categories of reported whole grain intake, from less than one and a half servings 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 a slice of whole grain bread, half a cup of rolled oats cereal, or half a cup of brown rice.
The results show that for each four-year interval:
Waist size increased by an average of more than 1 inch among the low-eating participants, compared to about ½ inch among the high-eating participants.
Even after accounting for changes in waist size, mean increases in blood sugar levels and systolic blood pressure were greater in low-intake participants than in high-intake participants.
The researchers also studied five risk factors in four categories of refined grain intake, from less than two servings per day to more than four servings per day. Low refined grain intake was associated with a smaller mean increase in waist size and a larger mean decrease in triglyceride levels over each four-year period.
“Our findings suggest that eating whole grains as part of a healthy diet has health benefits beyond just helping us lose or maintain weight as we age. Blood sugar and blood pressure over time. Managing these risk factors as we age can help prevent heart disease. may help protect,” said Nicola McKeon, senior and corresponding author and a scientist on the USDA HNRCA’s Nutritional Epidemiology Team.
“There are reasons why whole grains may work to help people maintain waist size and reduce the growth of other risk factors. The presence of dietary fiber in whole grains may have a satiating effect, and magnesium, potassium, and antioxidants may contribute to lowering blood pressure. Especially soluble fiber foods. —the latter may have a beneficial effect on blood sugar levels,” says Kaleigh Sawicki. Sawicki did this work as part of his doctoral dissertation while Gerald J. and Dorothy R. student at the Friedman School of Nutrition Science and Policy while working with the Nutritional Epidemiology Team at the USDA HNRCA.
The biggest contributors to whole grain intake among participants were whole-wheat bread and ready-to-eat whole-grain breakfast cereals. Refined grains mostly come from pasta and white bread. The difference in health benefits between whole and refined grains may be due to the fact that whole grains are less processed than refined grains. Whole grains have a fiber-rich outer layer and an inner germ layer containing B vitamins, antioxidants and small amounts of healthy fats. Combining whole grains removes these nutrient-dense ingredients, leaving only starch-packed refined grains behind.
“The average American eats about five servings of refined grains per day, far more than is recommended, so it’s important to think about ways to replace refined grains with whole grains throughout your day. For example, you might consider a bowl of whole grain cereal. For breakfast “Swap out a white flour bagel and replace refined-grain snacks, entrees and side dishes with whole-grain options. Small incremental changes in your diet to increase whole-grain consumption will make a difference over time,” says McKeon.
method
To measure daily grain intake, researchers used diet questionnaires that participants completed every four years from 1991 to 2014, resulting in an average of 18 years of data.
Dietary assessment data came from five study trials, and observations were only included if participants participated in at least two consecutive trials with accurate dietary data. Participants with diabetes at baseline were excluded.
The statistical analysis was adjusted for factors that may have influenced the results, including other aspects of a healthy diet. Limitations of the study include that food consumption is self-reported, and participants may over- or under-estimate certain foods based on perceived social desirability. Because of its observational design, the study does not reflect causal relationships.