L-theanine (present in green tea) shows interesting results in alpha wave brain activity: https://apjcn.nhri.org.tw/server/APJCN/17%20Suppl%201/167.pd... I think there was a post on hn about l-theanine before.
I have a noticeably positive response to taking Acytel L-carnitine. One pill at night before bed. Taking half the dosage on an empty stomach gives best results, though makes ones stomach a little queasy.