The study, published in the Journal of Clinical Investigation, reports that infusion of fat solution into the stomach of volunteers was associated with an activation of brain regions which reduced sad emotions.
The researchers led by Lukas Van Oudenhove, at the University of Leuven, Belgium, imaged changes in the brain when healthy non-obese individuals experience sadness. The team reported that administration of a fatty acid solution to the stomach attenuated the behavioural and nerve cell responses to sad emotion.
“We investigated the interaction between nutrient-induced gut-brain signalling and sad emotion induced by musical and visual cues at the behavioural and neural level in healthy non-obese subjects undergoing functional magnetic resonance imaging,” said Van Oudenhove and his colleagues.
“These findings increase our understanding of the interplay among emotions, hunger, food intake, and meal-induced sensations in health, which may have important implications for a wide range of disorders, including obesity, eating disorders, and depression,” they added.
Foods for moods?
It is well known that there is an intimate relationship between emotional state and food intake — we choose chocolate over an apple when overworked and stressed and comfort food makes us feel better.
The authors explained that an “intimate relationship between hunger/satiety, food intake, visceral sensory signalling, and emotions exists.”
“Feeding supplies essential nutrients, making it critical for survival. Hence, feeding regulatory mechanisms are firmly rooted in homeostasis, giving feeding its intrinsic rewarding nature,” they said.
“Although a relationship between emotional state and feeding behaviour is known to exist, the interactions between signalling initiated by stimuli in the gut and exteroceptively [externally] generated emotions remain incompletely understood,” said Van Oudenhove and his colleagues.
The new study investigated interactions between fatty acid–induced gut-brain signalling and experimentally induced sad emotion at both the behavioural and brain level in healthy volunteers.
The subjects received an internal infusion of fatty acid solution or saline during neutral or sad emotion induction and rated sensations of hunger, fullness, and mood.
When volunteers were given saline infusions, the authors reported that sad emotion were associated with a similar to normal activation in the brain
“However, most importantly, fatty acid attenuates the effect of sad emotion compared with saline,” said the researchers.
They said that the results demonstrate, “for what we believe to be the first time in humans”, that a purely internal, subliminal appetitive stimulus (fatty acid infusion in the fasted state) interacts with an externally generated negative emotional state, at both the behavioural and neural level.
“More specifically, fatty acid infusion attenuated both the behavioural and neural responses to sad emotion induction,” said Van Oudenhove and his team.
They added that the neuro-chemical mechanisms underlying this phenomenon as well as its physiological function remain unknown.
Source: Journal of Clinical Investigation
Published online ahead of print, doi: 10.1172/JCI46380
“Fatty acid–induced gut-brain signaling attenuates neural and behavioral effects of sad emotion in humans”
Authors: L. Van Oudenhove, S. McKie, D. Lassman2, B. Uddin, et al