A new study published in Cell Metabolism shows that up to 30 percent of people could have a higher sensitivity to melatonin, the sleepiness-inducing hormone that reduces the production of insulin. This is caused by a change to a melatonin receptor gene—the MTNR1B gene—that reduces the amount of insulin released by the pancreas, which makes the person more likely to develop type 2 diabetes.
It's important to note that MTNR1B isn't the only gene that makes people more susceptible to type 2 diabetes—in fact, there are hundreds. However, the study found that those with two copies of the gene have more melatonin receptors than those who have one or no copies.
During the study, non-diabetics were separated into two groups: One with the MTNR1B risk gene variant and one without. All participants took the same amount of a melatonin supplement every night. By the end of the three-month study period, the people who were lacking the risk gene had three times as much insulin as those who had it.
"We don't typically eat or are physically active at night, so our energy demands drop and we don't need maximum insulin secretion," says study author Hindrik Mulder of Lund University in Sweden and Leif Groop. "A likely explanation is that, as melatonin levels rise, they tell our beta cells not to release as much insulin."
This doesn't necessarily mean that people with MTNR1B can't ever take melatonin, but it does suggest that they might want to avoid prolonged use, according to authors of the study.
What do you think about the possible link between melatonin and type 2 diabetes?