reinforcing many of the inflammatory mechanisms making
you depressed to begin with!
SEROTONIN AND THE GUT
According to an oft-cited statistic, 90 percent of the body’s
supply of serotonin is found in the gut, not the brain. This is
true, as gut epithelial cells create serotonin, facilitating
digestion. Does the key to happiness, then, lie in the gut?
You bet—but the reason why may surprise you. Gut-derived
serotonin does not cross the blood-brain barrier. But at the
same time, what happens in the gut can influence brain
serotonin activity via its ability to modulate inflammation.
In chapter 7, we discussed gut health and the necessity
for maintaining gut barrier integrity by consuming soluble
fiber–containing vegetables that help to “seal up” the gut’s
pores. Lipopolysaccharide (LPS), a normal constituent of a
healthy bowel, becomes a potent instigator of inflammation
when seeped through a “leaky” gut. Aside from sending the
immune system into an inflamed state of defense, LPS is
directly toxic to both the serotonin and dopamine systems.
In fact, LPS is often used in the lab setting, injected into
mice to induce depressive behavior and neurodegeneration.
Revisit chapter 7 for ways to protect and enhance your gut
wall integrity.