An Integrative MD Explains The Sneaky Link Between Melatonin & Metabolism

Melatonin is one impressive hormone. Not only does it send sleepy-time signals to your body, but it also has antioxidant and anti-inflammatory properties that can benefit mitochondrial function and even skin health. Not to mention, melatonin plays a role in fertility: "One of the richest sites of melatonin in the body is the ovaries," midwife and integrative medicine doctor Aviva Romm, M.D., says on the mindbodygreen podcast. "And fertility actually depends on healthy melatonin levels in the brain and in the ovaries."

Again, melatonin is a workhorse that you'll want to make sure you have enough of. Your brain (pineal gland) naturally produces the majority of endogenous melatonin. But when it comes to taking melatonin supplements (i.e., exogenous melatonin), some concerns do arise: There's the dosage point—where some research suggests that taking too much melatonin over time may adversely affect other hormones1—and there's a much sneakier hitch Romm says is important to keep in mind. 

When melatonin gets released at night, the hormone sends signals to your body that it's time to start winding down. As a result, your body goes into "rest mode," with a focus on repair and restoration—and daytime functions like digestion slow down. (That's why experts say to avoid eating late at night, when your metabolism is naturally slower, if you can.) 

When you take melatonin, you kick-start this rest-and-recover process. So if you take the sleep aid, say, right after eating, you could impinge on your digestion without even knowing it. "If you eat your dinner late, let's say 7:30 p.m., and then you take your melatonin at 8 p.m., you may be quieting your metabolism a little bit," says Romm. "You may not get as much digestive fire, and it may actually affect weight gain." 

Of course, there's an easy fix here: Just space out the time between eating and taking your melatonin. "If that means you need to bump your dinner a little earlier or take your melatonin a little later, that seems to be the antidote," Romm adds.