The new study indicates that a persons’ 24-hour circadian clock plays an important role in glucose tolerance. Here the research revealed that due to the body’s circadian rhythm, human glucose tolerance is lowered during the night hours. This happens even if “day” and “night” times are reversed under laboratory conditions.
Internal body clocks, called circadian clocks, regulate the daily “rhythms” of many bodily functions, from waking and sleeping to body temperature and hunger. Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism’s environment.
In the research paper, neuroscientist Frank Scheer (Division of Sleep and Circadian Disorders), from the Brigham and Women’s Hospital in Boston, writes: “In a prior study, we found that when behavior cycles of feeding and sleeping are not in normal alignment with the internal body clock, that this negatively affects the regulation of blood sugar and especially glucose tolerance.”
The main aim of the study was to understand the effects of eating and sleeping behaviors compared with the circadian clock on glucose tolerance. To show this, the Boston based researchers mimicked night-shift work in 14 people under controlled laboratory conditions. Participants spent eight days on a typical day-shift schedule, which involved eating breakfast at 8 a.m., dinner at 8 p.m., and sleeping during the night. Four weeks on, the same people had their days reversed. This meant they then ate breakfast at 8 p.m., had dinner at 8 a.m. They slept during the day.
What happened next is outlined by study coauthor Christopher Morris, an instructor of medicine at the Division of Sleep and Circadian Disorders at Harvard Medical School, who told The Scientist: “We showed that glucose levels after identical meals were 17 percent higher in the evening than in the morning, independent of when a participant had slept or had their meals.” This means that glucose tolerance was considerably affected by the work, sleep and meal patterns being reversed. Higher glucose (blood sugar) levels are associated with diabetes.
Therefore, the results suggest that, rather than behavioral cycles, the body clock controls the body’s daily glucose tolerance. This means that circadian rhythms and respecting the natural body clock have implications for shift workers.
The research has been published in the journal PNAS. The research is titled “Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans.”
