Study Shows How Walnuts Affect The Brain, Decrease Hunger

Maintaining a healthy weight helps with diabetes management, and now researchers at Beth Israel Deaconess Medical Center (BIDMC) have validated that eating walnuts is helpful for appetite control.

“We don't often think about how what we eat impacts the activity in our brain,” said researcher Olivia M. Farr, Ph.D., an instructor in medicine in the Division of Endocrinology, Diabetes and Metabolism at BIDMC. “We know people report feeling fuller after eating walnuts, but it was pretty surprising to see evidence of activity changing in the brain related to food cues, and by extension what people were eating and how hungry they feel.”

For the study, ten volunteers with obesity stayed at the BIDMC’s Clinical Research Center for two five-day sessions, so their food intake could be accurately monitored. During one five-day session, participants were given daily smoothies containing 48 grams of walnuts. During the other five-day session, each received the same daily smoothie, but without walnuts.

As with earlier observational studies, the participants reported less hunger during the walnut smoothie five-day session, than during the non-walnut smoothie session. To understand this better, MRI tests were administered on each session’s fifth day, while participants looked at pictures of tempting foods.

After eating the walnut-rich diet, food pictures triggered enhanced activity in the brain’s right insula, when compared to brain activity after the non-walnut diet.

“This is a powerful measure,” says researcher Dr. Christos Mantzoros, director of the Human Nutrition Unit at BIDMC, and Harvard Medical School professor. “We know there's no ambiguity in terms of study results. When participants eat walnuts, this part of their brain lights up, and we know that's connected with what they are telling us about feeling less hungry or more full.”

The brain’s right insula is thought to be associated with cognitive control and attentiveness to what is important. So, when activated, it can help us select healthier food options over less healthy ones.

“From a strategic point of view, we now have a good tool to look into people's brains - and we have a biological read out.” said Mantzoros. “We plan to use it to understand why people respond differently to food in the environment and, ultimately, to develop new medications to make it easier for people to keep their weight down.”

Source: BIDMC
Photo credit: U.S. Dept. of Agriculture