YSK: Approximately 90-95% of your body's serotonin supply is produced in your GI tract. Poor gut health can not only impact you physically, but mentally as well.
from /r/YouShouldKnow
YSK: 体内のセロトニンの約90〜95％は、消化管で生成されます。腸内環境が悪いと、身体的な影響だけでなく、精神的にも影響が出てきます。