How the timing of dinner and genetics affect individuals’ blood sugar control
Massachusetts General Hospital
In research published in Diabetes Care, a team
led by investigators at Massachusetts General Hospital (MGH), Brigham and
Women's Hospital (BWH) and the University of Murcia in Spain conducted a
clinical trial to look for connections between these two factors.
"We
decided to test if late eating that usually occurs with elevated melatonin
levels results in disturbed blood sugar control," says senior author Richa
Saxena, PhD, a principal investigator at the Center for Genomic Medicine at
MGH.
For the randomized crossover study that included 845 adults from Spain, each participant fasted for eight hours and then for the next two evenings had first an early meal and then a late meal relative to their typical bedtime. The investigators also analyzed 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," explains 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 dinner timing also resulted in lower insulin
levels and higher blood sugar levels. (This connection makes sense because
insulin acts to decrease blood sugar levels.) In the late dinner timing, participants
with the MTNR1B G-allele had higher blood sugar levels than
those without this genetic variant.
"We
found that late eating disturbed blood sugar control in the whole group.
Furthermore, this impaired glucose control was predominantly seen in genetic
risk variant carriers, representing about half of the cohort," says lead
author Marta Garaulet, PhD, a professor of physiology and nutrition in the
Department of Physiology at the University of Murcia.
Experiments
revealed that the high melatonin levels and carbohydrate intake associated with
late eating impairs blood sugar control through a defect in insulin secretion.
"Our
study results may be important in the effort towards prevention of type 2
diabetes," says 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 industrialized 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 note 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
personalized behavioral recommendations," says 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."
Funding
for the study was provided by the National Institutes of Health, the Spanish
Government of Investigation and the Seneca Foundation.