As some of us are getting 23andme results, I want to post some of the stuff I'm connecting. I have my results and dh's, but we didn't test the kids and so I'm guessing with them.
First, MAO-A, that's the swingy serotonin one, that makes you want quiet time so you don't get overstimulated. Dh has that one, and I don't. He likes to stay home, will play video games and watch movies for a chance to 'relax his brain' and really does well with time to specifically work on his own projects without interruption. I, on the other hand, tend towards low serotonin in general. I like activities that boost serotonin, getting out, talking to people, finishing projects, exploring new places, etc. I DON'T like recharging time. I like momentum. After one fun thing, I want it to keep going forever, or I want to jump straight into the next thing. I guessed that dd was more like dh - she really likes to watch her videos, and they seem to reset her. And I guessed that ds (the baby) was more like me - he just wants to go go go, explore everything. Turns out this gene is sex-linked on the X chromosome. Since I'm -- and dh is +, that makes dd +- and ds -. So I guessed right!
So how is this helpful? Differentiating the different serotonin types into groups, like those who need that recharge time vs those who want to go go go can give us tools for better meeting each person's needs, to keep their serotonin in a good spot. I don't think there are specific nutrients for this one, per se, but it's where behavior has strong influences on brain chemistry.