Melatonin is a pro-oxidant

Another study shows that melatonin acts as pro-oxidant.

“It was long believed that melatonin might counteract intracellular oxidative stress because it was shown to potentiate antioxidant endogenous defences, and to increase the activity of many antioxidant enzymes.

However, it is now becoming evident that when radicals are measured within cells, melatonin increases, rather than decreasing, radical production.

Herein we demonstrate a pro-oxidant effect of melatonin in U937 cells by showing an increase of intracellular oxidative species and a depletion of glutathione (GSH).”

I wonder if our bodies are smart enough to lower melatonin production when they are in chronic oxidative stress. E.g. reduction of SAMe -> oxidation of cobalamin -> lowered metabolic rate -> less melatonin is made -> sleep problems.