Caution is advised regarding melatonin supplementation due to its potent effects on cardiovascular function, immune function, anti-cancer properties, bone mass, and gonadal function.

“now that you understand how potently melatonin can impact things like cardiovascular function, immune function, anti-cancer properties, bone mass, gonad function, et cetera, you can understand why it would make sense to be cautious about melatonin supplementation, because supplementation tends to be pretty static. It's X number of milligrams per night, whereas normally endogenously the amount of melatonin that you're releasing each night is changing according to time of year, or if you happen to live in an area where there isn't much change in day length across the year, so for instance, if you live near the equator, well, then your body is accustomed to having regular amounts of melatonin each night. When you start supplementing melatonin, you start changing the total amount of melatonin, obviously, but you're also changing the normal rhythms in how much melatonin is being released into your brain and body across the 365-day calendar year.