CO2, vitamin K, red light, avoiding PUFA
CO2 and avoiding PUFA especially.
I got something called a Quantum Pendant several months ago but I don't know if it's really doing anything (be careful if you decide to get this because there are several fakes)
two other things that help are the sitali/sitkari pranayamas (easy find on Google), and inhaling through my left nostril, retaining it, and exhaling out my right nostril. I think these techniques lower serotonin and EMF really increases serotonin.