July 13 (UPI) -- Older adults who eat at least three servings of whole grains every day experience smaller increases in waist size, blood pressure and blood sugar compared with those who consume less than one-half serving per day, a study published Tuesday by the Journal of Nutrition found.
Over a four-year period, adults in their mid-50s and older who ate at least three servings of whole grains daily added an average of one-half inch to their waist size, the data showed.
Those in the "low-intake" group, meanwhile, added 1 inch, on average, the researchers said.
In addition, study participants, on average, had blood pressure readings of approximately 125 over 75, but those who consumed at least three servings of whole grains daily measured, on average, 122 over 74.
Similarly, participants had average fasting blood sugar levels of 95 milligrams per deciliter, with those consuming recommended daily amounts measuring about 1% lower, they said.
"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," study co-author Nicola McKeown said in a press release.
"Managing these risk factors as we age may help to protect against heart disease," said McKeown, a scientist on the Nutritional Epidemiology Team at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston, Mass.
Dietary Guidelines published by the U.S. Department of Agriculture and U.S. Department of Health and Human Services recommend three or more servings of whole grains 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, according to the guidelines.
The difference in health benefits between whole and refined, or processed, grains may occur because whole grains are less processed than refined grains, the researchers said.
Whole grains have a fiber-rich outer layer and an inner germ layer packed with B vitamins, antioxidants and small amounts of healthy fats, but as they are processed, the nutrient-dense components in refined grains are removed.
For this study, McKeown and her colleagues analyzed data from the Framingham Heart Study Offspring Cohort, ongoing research to assess long-term risk factors for heart disease.
They examined health outcomes associated with whole- and refined-grain consumption over nearly 20 years for 3,100 adults in their mid-50s at the start of data collection.
To measure daily grain intake, the researchers used diet questionnaires that participants completed every four years from 1991 to 2014.
Even after accounting for changes in waist size, average increases in blood sugar levels and blood pressure were greater in participants with low whole-grain intake compared with those with high whole-grain intake, the data showed.
For example, those with the lowest levels of whole grains in their diet had above average blood pressure, blood sugar and cholesterol levels.
In addition, 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.
The most common source of whole-grain intake among participants was whole-wheat breads and ready-to-eat whole-grain breakfast cereals, while most of the refined grains consumed by study participants came mostly from pasta and white bread, according to the researchers.
"The average American consumes about five servings of refined grains daily, much more than is recommended, so it's important to think about ways to replace refined grains with whole grains throughout your day," McKeown said.
"Small incremental changes in your diet to increase whole-grain intake will make a difference over time," she said.