Andrew Huberman· PhD
And I really want to drive home this point of baselines and peaks. The baseline level of serotonin might set our overall mood, whether or not we wake up feeling pretty good or really lousy if our serotonin levels happen to be very, very low, whether or not we tend to be in a kind of a calm space or whether or not we tend to be somewhat irritable. But then of course individual events as we go about our day, maybe a compliment that we get or maybe somebody says something irritating to us, whatever it may be will also influence levels of serotonin, but those serotonin events are going to be related to events at particular neural circuits in the brain. And this is an important topic because I think that a lot of people hear quite accurately, oh, 90 to 95% of our serotonin is manufactured in the gut. And indeed that's true. It's manufactured from the sorts of microbiota that I just described. And there are many, many experiments now, mostly in animal models, but also some in humans that show that if the gut microbiome is deficient in some way to these particular bacteria, that serotonin levels drop and people's mood suffers, maybe even their immune system functions, maybe even it exacerbates certain psychiatric illnesses. However, a lot of people take that to mean that the serotonin of the brain all comes from the gut or mostly comes from the gut. That's not the case.