Trending Clinical Topic: Melatonin

Ryan Syrek


February 18, 2022

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Recent findings related to melatonin, both the supplement and the naturally produced form, resulted in this week's top trending clinical topic. Findings from the MTNR1B SNP*Food Timing Interaction on Glucose Control (ONTIME-MT), a randomized crossover study, were recently published in Diabetes Care (see Infographic).

The study found that people who are carriers of the G allele of the melatonin receptor 1b gene (MTNR1B) have increased glucose tolerance impairment after eating a late dinner. The discovery of MTNR1B as a type 2 diabetes–associated gene "suggests that beyond sleep and circadian regulation, melatonin plays a key role in glucose metabolism," the authors note.

The research included 845 adults in Spain who were aged 18-70 years and did not have diabetes. The mean age of the participants was 38 years, and 71% were women. They had a mean body mass index of 25.7, and 18% had obesity. Participants ate dinner at an average of 21:38 (9:38 PM) and went to bed at 24:32 (12:32 AM). DNA analysis determined that 50% of the participants had the CC genotype of the MTNR1B gene, 40% had the CG genotype, and 10% had the GG genotype.

Each participant fasted for 8 hours and then had a 2-hour 75-g oral glucose tolerance test either 1 hour before bedtime (a late dinner) or 4 hours before bedtime (an early dinner). The test was repeated at the opposite dinner time on a different night. Average serum melatonin values were 3.5-fold higher after the late dinner compared with the early dinner, resulting in 6.7% lower insulin area under the curve (AUC) and 8.3% higher glucose AUC.

In terms of melatonin supplements, a recent study found increasing popularity. The use of over-the-counter melatonin increased fivefold over the past two decades in the United States, according to a research letter in JAMA. Researchers tracked data from the National Health and Nutrition Examination Survey from 1999-2000 to 2017-2018 and focused on respondents aged 20 years or older (n = 55,021; mean age, 47.5 years; 52% women). The study found that the overall reported weighted prevalence of melatonin use grew from 0.4% (95% CI, 0.2%-1.0%) in 1999-2000 to 2.1% (95% CI, 1.5%-2.9%) in 2017-2018 (linear P = .004).

Melatonin supplements are now available in tablets, capsules, gummies, powders, liquids, sprays, and other formulations. Users can even buy CBD-melatonin combos. Data have showed that melatonin supplements reduce the time it takes to fall asleep by 4 minutes. A recent study found a specific benefit in patients with multiple sclerosis (MS), a group for whom objective studies of sleep problems are scarce. The double-blind, placebo-controlled, crossover study included participants with MS who had a Pittsburgh Sleep Quality Index (PSQI) score of 5 or more or an Insomnia Severity Index (ISI) score higher than 14 at baseline. Half of the 30 participants received melatonin for the first 2 weeks and then switched to placebo. The other half started with placebo and moved over to melatonin at the beginning of week 3. Melatonin improved average sleep time (6.96 vs 6.67 hours; P = .03). Sleep efficiency was also nominally improved (84.7% vs 83.2%), although the result was not statistically significant (P = .07).

From its use to produce sleep in those with MS and without, to its potential role in the development of diabetes, investigations into the increasingly popular hormone made melatonin this week's top trending clinical topic.

Learn more about melatonin.


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