Ai Takehana, a researcher at the Faculty of Informatics, Gunma University (at the time of the research) and Professor Koji Jimura, in collaboration with Professor Norihiro Sadato of the National Institute for Physiological Sciences, National Institutes of Natural Sciences, Professor Junichi Chikazoe, a team leader of Araya, and Professor Teppei Matsui of Doshisha University Graduate School of Brain Sciences, have found that when humans choose "tasty but unhealthy foods" over "delicious but unhealthy foods," the prefrontal cortex is active. They found that the prefrontal cortex is activated when people choose "healthy but not tasty food" over "tasty but not healthy food," and that this activity is greater in people with a strong sense of self-control who maximize the long-term benefit. The findings suggest that the prefrontal cortex's mechanisms of self-control play an important role when humans make food choices that prioritize health. The study was published July 26 in the American journal Cerebral Cortex.

1. key points of this study

• We measured human brain activity when people value health over taste in food selection.
• The strength of "restraint" was measured as the degree to which they prioritize long-term interests in their choice of monetary rewards.
• When health was more important than taste, the prefrontal cortex was activated.
• Prefrontal cortex activity was greater in those with stronger self-control.

2. outline of this study

When choosing food, it is important that it tastes good and is healthy. Eating healthy food is good for one's own health. However, despite the fact that we all know this, we often impulsively choose unhealthy foods in favor of good taste. For example, we have all had the experience of reaching for foods that are high in fat, sugar, and carbohydrates, even though we know they are not very healthy. In other words, making healthy food choices a priority is not easy. This is because choosing foods that emphasize health over taste requires "self-control" to prioritize the long-term benefit of health over the immediate benefit of taste. So how does the human brain function when making health-conscious food choices? And how is brain activity related to self-control?

THIS RESEARCH GROUP MEASURED BRAIN ACTIVITY IN A SITUATION IN WHICH HUMAN SUBJECTS CHOSE FOODS INDEXED FOR TASTE AND HEALTH. FIRST, SUBJECTS RATED FOODS ACCORDING TO WHETHER THEY WERE TASTY AND HEALTHY, AND CATEGORIZED THEM AS "TASTY BUT NOT HEALTHY" OR "HEALTHY BUT NOT TASTY" FOODS. THEN, DURING THE MEASUREMENT OF BRAIN ACTIVITY, THE SUBJECTS SELECTED WHICH OF THESE TWO TYPES OF FOODS THEY WANTED TO EAT FROM THOSE DISPLAYED ON THE SCREEN (FIGURE A). HERE, IF THE PARTICIPANTS CHOSE "HEALTHY BUT NOT TASTY FOODS" INSTEAD OF "TASTY BUT NOT HEALTHY FOODS," IT CORRESPONDS TO THE FACT THAT THEY PLACED MORE IMPORTANCE ON HEALTH THAN ON TASTINESS.

IN ADDITION, THE STRENGTH OF RESTRAINT WAS MEASURED BY A TASK IN WHICH PARTICIPANTS HAD TO CHOOSE A FUTURE MONETARY REWARD (FIGURE B). IN THIS TASK, PARTICIPANTS WERE ASKED TO CHOOSE ONLY ONE OF TWO REWARDS THAT DIFFER IN TIME AND AMOUNT TO BE EARNED. FOR EXAMPLE, THE PARTICIPANTS COULD CHOOSE EITHER "5,000 YEN RIGHT NOW" OR "10,000 YEN IN ONE YEAR. HERE, THE CHOICE OF "5,000 YEN RIGHT NOW" IS THE RESULT OF PRIORITIZING IMMEDIATE PROFIT AND IS IMPULSIVE. ON THE OTHER HAND, THE CHOICE OF "RECEIVE 10,000 YEN IN ONE YEAR" MEANS THAT THE LONG-TERM PROFIT IS PRIORITIZED OVER THE IMMEDIATE PROFIT AND THAT THE PERSON HAS A STRONG SENSE OF SELF-CONTROL. IN OTHER WORDS, A PERSON WHO CHOOSES TO WAIT UNTIL HE OR SHE EARNS BUT A LARGER AMOUNT OF REWARD IS MORE SELF-CONTROLLED.

WHEN WE EXAMINED BRAIN ACTIVITY IN FOOD CHOICE, WE OBSERVED GREATER ACTIVITY IN THE PREFRONTAL CORTEX WHEN PEOPLE CHOSE "HEALTHY BUT NOT TASTY FOODS," I.E., WHEN THEY MADE CHOICES THAT EMPHASIZED HEALTH OVER TASTE (FIGURE C, LEFT). FURTHERMORE, WE FOUND THAT BRAIN ACTIVITY IN THESE REGIONS WAS GREATER IN HUMANS WHO PRIORITIZE LONG-TERM BENEFITS IN MONETARY REWARDS, I.E., THOSE WHO ARE MORE SELF-CONTROLLED (FIGURE C RIGHT). ON THE OTHER HAND, ALTHOUGH IT HAS BEEN THOUGHT THAT THE STRENGTH OF SELF-CONTROL IS RELATED TO THE FUNCTION OF COGNITION, OUR RESULTS SUGGEST THAT THE FUNCTION OF COGNITION IS NOT RELATED TO THE PRIORITY OF HEALTH IN FOOD CHOICES.

The results of this study suggest that when humans make food choices based on health over taste, prefrontal cortex activity associated with restraint in prioritizing long-term interests plays an important role. Although food choice is an important behavior for other animal species, making choices based on the long-term benefit of prioritizing health seems to be characteristic of humans, and it is interesting that the prefrontal cortex, which is most developed in humans, is involved in prioritizing health. And the group believes that this prefrontal mechanism of self-control may be important for the continuation of healthy eating habits.

3. information on the original paper

Takehana A, Tanaka D, Arai M, Hattori Y, Yoshimoto T, Matsui T, Sadato N, Chikazoe J, Jimura K (2024) Healthy dietary choices involve prefrontal mechanisms associated with long-term reward maximization but not working memory. Cerebral Cortex 34, bhae302.

4. related links

Papers Presented
https://academic.oup.com/cercor/article/34/7/bhae302/7721467
https://doi.org/10.1093/cercor/bhae302

Laboratory of Cognitive Neuroscience, Faculty of Informatics, Gunma University
https://ja.jimuralab.org/

Faculty of Informatics, Gunma University
https://www.inf.gunma-u.ac.jp/

National Institute of Physiological Sciences, National Institutes of Natural Sciences
https://www.nips.ac.jp/