Saxena Lab

How timing of dinner and genetics affect blood sugar level control

Originally appeared in Health Europa, January 26, 2022.

Genetics of Circadian Rhythms Research Area

Researchers conducted a trial to understand the connection between disturbed blood sugar level control and the timing of meals relative to sleep.

Blood sugar level control, which is impaired in individuals with diabetes, is affected by various factors, including the timing of meals relative to sleep and melatonin levels, a hormone primarily released at night that helps control sleep-wake cycles.

Investigators at Massachusetts General Hospital (MGH), Brigham and Women’s Hospital (BWH) and the University of Murcia in Spain performed a clinical trial to connect blood sugar level control and meal timings.

Senior author, Richa Saxena, PhD, a principal investigator at the Center for Genomic Medicine at MGH, addressed the study: “We decided to test if late eating that usually occurs with elevated melatonin levels results in disturbed blood sugar control.”

The research was published in Diabetes Care.

Late-night eating and disturbed blood sugar level control

The randomised crossover study included 845 adults from Spain. Each participant was asked to fast for eight hours, then for the next two evenings have an early meal and then a late meal relative to their typical bedtime. The researchers also analysed each participant’s genetic code within the melatonin receptor-1b gene (MTNR1B) because previous research has linked a variant (called the G-allele) in MTNR1B with an elevated risk of type 2 diabetes.

“In natural late eaters, we simulated early and late dinner timing by administering a glucose drink and compared effects on blood sugar control over two hours,” explained Saxena. “We also examined differences between individuals who were carriers or not carriers of the genetic variant in the melatonin receptor.”

The team found that melatonin levels in participants’ blood were 3.5-fold higher after the late dinner. The late dining timing also impacted insulin levels and the researchers found these levels had lowered whilst blood sugar levels were higher. Insulin acts by decreasing blood sugar levels; therefore, this finding makes sense.

“We found that late eating disturbed blood sugar level control in the whole group. Furthermore, this impaired glucose control was predominantly seen in genetic risk variant carriers, representing about half of the cohort,” said lead author Marta Garaulet, PhD, a professor of physiology and nutrition in the Department of Physiology at the University of Murcia.

High melatonin levels and carbohydrate intake

Experiments revealed that the high melatonin levels and carbohydrate intake associated with late-night eating impair blood sugar level control through a defect in insulin secretion.

“Our study results may be important in the effort towards prevention of type 2 diabetes,” commented co-senior author Frank A.J.L. Scheer, PhD, MSc, director of the Medical Chronobiology Program at BWH. “Our findings are applicable to about a third of the population in the industrialised world who consume food close to bedtime, as well as other populations who eat at night, including shift workers, or those experiencing jetlag or night eating disorders, as well as those who routinely use melatonin supplements close to food intake.”

The authors noted that for the general population, it may be advisable to abstain from eating for at least a couple of hours before bedtime.

“Genotype information for the melatonin receptor variant may further aid in developing personalised behavioural recommendations,” said Saxena. “Notably, our study does not include patients with diabetes, so additional studies are needed to examine the impact of food timing and its link with melatonin and receptor variation in patients with diabetes.”