Double whammy for two popular medical dogmas. One of them is that serotonin is the “happy hormone” and raising its levels has a variety of benefits, one of which is reducing anxiety. After all, it is hard to be happy if anxiety is through the roof, right? The second one is that low-carb/high-fat diets (also known as keto diets) are the best thing for health since the advent of antibiotics. Well, wrong on both counts, according to the study below. It found that a high-fat (45% of calories) diet caused anxiety by increasing serotonin production in the gut. It actually increased the expression of the enzyme tryptophan hydroxylase (TPH), which is even worse than simply increasing serotonin production directly since increased expression levels can persist for a long time and often do not decline back to baseline even if the offending (TPH-increasing) factor has been removed from the organism. The study actually refutes yet another medical dogma, which claims that gut-derived serotonin does not have central effects since it is unable to cross the blood-brain barrier. Considering the ubiquity of SSRI drugs, low-carb diets, and exhaustive exercise (which also boosts serotonin production) it is little wonder that anxiety rates are skyrocketing and it is now the most common mental health disorder.
https://biolres.biomedcentral.com/articles/10.1186/s40659-024-00505-1
https://www.colorado.edu/today/2024/06/13/how-high-fat-diet-could-make-you-anxious
“…When we’re stressed out, many of us turn to junk food for solace. But new CU Boulder research suggests this strategy may backfire. The study found that in animals, a high-fat diet disrupts resident gut bacteria, alters behavior and, through a complex pathway connecting the gut to the brain, influences brain chemicals in ways that fuel anxiety.”
“…When compared to the control group, the group eating a high-fat diet, not surprisingly, gained weight. But the animals also showed significantly less diversity of gut bacteria. Generally speaking, more bacterial diversity is associated with better health, Lowry explained. They also hosted far more of a category of bacteria called Firmicutes and less of a category called Bacteroidetes. A higher Firmicutes to Bacteroidetes ratio has been associated with the typical industrialized diet and with obesity. The high-fat diet group also showed higher expression of three genes (tph2, htr1a, and slc6a4) involved in production and signaling of the neurotransmitter serotonin—particularly in a region of the brainstem known as the dorsal raphe nucleus cDRD, which is associated with stress and anxiety. While serotonin is often billed as a “feel-good brain chemical,” Lowry notes that certain subsets of serotonin neurons can, when activated, prompt anxiety-like responses in animals. Notably, heightened expression of tph2, or tryptophan hydroxylase, in the cDRD has been associated with mood disorders and suicide risk in humans. “To think that just a high-fat diet could alter expression of these genes in the brain is extraordinary,” said Lowry. “The high-fat group essentially had the molecular signature of a high anxiety state in their brain.”
