More servings of whole grains linked to slower memory decline in Black people

Black people who eat more foods with whole grains, including some breads and cereals, quinoa, and popcorn, may have a slower rate of memory decline compared to Black people who eat fewer whole grain foods, according to a study published in the November 22, 2023, online issue of Neurology. The researchers did not see a similar trend in white participants.

The study does not prove that eating more whole grains slows memory decline; it only shows an association.

The study found that among Black people, those who ate the most whole grains had lower levels of memory decline—equivalent to being 8.5 years younger than those who ate small amounts of whole grains.

"With Alzheimer's disease and dementia affecting millions of Americans, finding ways to prevent the disease is a high public health priority," said study author Xiaoran Liu, Ph.D., MSc, of Rush University in Chicago. "It's exciting to see that people could potentially lower their risk of dementia by increasing their diet of whole grains by a couple of servings a day."

The study involved 3,326 people with an average age of 75 without dementia. Of all participants, 1,999 people, or 60%, were Black. They were followed for an average of six years.

They filled out a questionnaire every three years on how often they ate whole grains. They also completed cognitive and memory tests every three years, including recalling lists of words, remembering numbers and putting them in the correct order.

Participants were then divided into five groups based on the amount of whole grains they had in their diet. The lowest group consumed less than half a serving per day, and the highest group consumed 2.7 servings per day.

The Dietary Guidelines for Americans recommend at least three servings of whole-grain foods daily. One serving of whole grains is equivalent to an ounce of food, such as one slice of bread, a half cup of cooked pasta or rice, an ounce of crackers or a cup of dry cereal.

Researchers found that a higher proportion of Black participants had more than one serving per day of whole grains than white participants, with 67% and 38%, respectively.

To determine rates of cognitive decline, researchers used an overall global cognition score summarizing four cognitive tests and examined their change over time.

After adjusting for factors that could affect the rate of cognitive decline, such as age, sex, education and smoking, researchers found that the global cognitive score of Black people who had the highest intake of whole grains, or more than three servings a day, declined at a rate of 0.2 standard deviation units per decade more slowly than Black people who had the lowest intake, or less than one serving per day.

"These results could help medical professionals make tailored diet recommendations," Liu added. "More large studies are needed to validate our findings and to further investigate the effect of whole grains on cognition in different racial groups."

A limitation of the study is that the food frequency questionnaire was self-reported, so people may not accurately remember what they ate.