I am sure I will get a lot of hate-mail about this, but frankly this is not really news. What is novel about this study is its finding that high-fat diet not only increased cortisol and 5-HT production, but also strongly decreased the ability of the organism to deactivate 5-HT through the so-called serotonin transporter (SERT). Namely, the high-fat diet decreased the expression of SERT, this further exacerbating the hyper-serotonin state – i.e. a double-whammy, which results in leaky gut and systemic inflammation (affecting even the brain).
https://doi.org/10.1080/1028415X.2025.2539320
A high-fat diet severs the chemical link between gut and brain
“…The investigation begins in the digestive tract, where specialized cells called enterochromaffin cells manufacture the vast majority of the body’s serotonin. The researchers report that a high-fat diet forces these cells to overproduce the chemical. This occurs because the diet stimulates the enzymes responsible for initiating synthesis. Simultaneously, the cellular machinery designed to recycle serotonin malfunctions. Under normal circumstances, a transporter protein acts like a vacuum to clear used serotonin from the system. The study indicates that fatty foods suppress the production of this transporter. This double blow of increased production and decreased cleanup causes serotonin to accumulate rapidly in the gut. This local surplus creates a toxic environment in the digestive system. The review explains that excess serotonin stimulates immune cells to release inflammatory signals. It also compromises the lining of the intestines. This loss of integrity leads to permeability issues often described as a “leaky gut,” allowing harmful substances to enter the bloodstream.”
“…Cortisol, the body’s primary stress hormone, also plays a significant role in this cascade. The researchers note that high-fat diets elevate circulating cortisol levels….”
