TH and attention deficit-hyperactivity disorder: In addition to reducing inflammatory cytokines,54 short chain fatty acids can impact neurotransmitters such as dopamine, norepinephrine, and serotonin by increasing the rate-limiting enzymes, tyrosine hydroxylase and tryptophan hydroxylase, which produce these neurotransmitters.55,56 As changes in neurotransmitter regulation like dopamine are theorized to be correlated with ADHD symptoms, the connection between short chain fatty acids and neurotransmitters is a potential future research direction.