A new research study has revealed that the consumption of walnuts activates senses in brain associated with the regular sensation of hunger of cravings. The first-of-its kind study involved brain imaging and took place at the Beth Israel Deaconess Medical Center (BIDMC). Findings of the study, published in the Diabetes, Obesity and Metabolism journal online, highlight for the first time the neurocognitive influence of the nuts on the brain. The study was supported by the California Walnut Commission (CWC) via an investigator-initiated funding.
While it has been known that people feel fuller after consuming walnuts, the study shows evidence of the change in activity in the brain concerned with food cravings, and is an evidence that shows what people eat has a connection with the feeling of hunger. To analyze exactly how the nuts suppress food cravings, the research team made use of functional magnetic resonance imaging (fMRI) and observed how the consumption of walnuts changed brain activity.
For the research, the researchers took help of 10 obese volunteers. The volunteers lived in the Clinical Research Center of BIDMC and attended two sessions of five-days each. Amid a controlled environment, the researchers kept a track of the exact nutritional intake of all the volunteers. During one of the five-day session, the volunteers consumed smoothies having 48 grams of the nut every day. During the other five-day session, the volunteers received nutritionally equal but walnut-free placebo smoothies that tasted exactly the same as the ones containing walnut.
The order of the sessions with the two different smoothies was made random, which meant that some volunteers consumed the walnut smoothie first while some consumed the placebo smoothie first. Neither the researcher nor the volunteers knew which smoothie was consumed during which session.
When undergoing fMRI tests on the fifth day of the study, researchers showed the volunteers images of food items, some highly desirable like desserts and hamburgers and some undesirable like vegetables. When shown the pictures of hamburgers and desserts, fMRI results revealed that there was an increase in activity in the right insula of the brain after the volunteers had consumed walnut-rich diet as compared to when they had consumed the placebo diet.
This part of the brain is involved in salience and cognitive control, which indicates that the volunteers were paying more attention to the available food choices and choosing healthier and less desirable food items over the most desirable ones.