New Delhi: Exposure to natural light may help treat and prevent type 2 diabetes, according to a small study.
The research, presented at the annual meeting of the European Association for the Study of Diabetes (EASD) in Germany from October 2-6, carried out a range of metabolic tests on a group of people with type 2 diabetes when they were exposed to natural light and when they were exposed to artificial light and compared the results. “The misalignment of our internal circadian clock with the demands of a 24/7 society is associated with an increased incidence of metabolic diseases, including type 2 diabetes,” said Ivo Habets of Maastricht University, the Netherlands, who co-led the research.
“Natural daylight is the strongest zeitgeber, or environmental cue, of the circadian clock, but most people are indoors during the day and so under constant artificial lighting,” said Habets.
The yet-to-be peer-reviewed study involved 13 participants with an average age of 70 years who stayed in research facilities, which allowed their light exposure, meal, and activity patterns to be tightly controlled.
They were exposed to two lighting conditions during office hours (8 am to 5 pm) in a randomised cross-over fashion: natural daylight from windows and artificial LED lighting.
There was a gap of at least four weeks between the two interventions, each lasting 4.5 days. During the natural daylight intervention, the light intensity was usually highest at 12:30 pm, with an average reading of 2453 lux.
The artificial light was a constant 300 lux. Evenings were spent in dim light (less than 5 lux), and the sleeping period (11 pm to 7 am) in darkness. The participants were provided with standardised meals, meaning they ate the same food in both interventions.
Blood sugar levels were continuously recorded by monitors worn on the upper arm, and a range of other tests were performed on the final day and a half of each intervention.
The study found that blood glucose levels were within the normal range (4.4-7.8 mmol/L) for longer during the natural daylight intervention than in the artificial light intervention.
The respiratory exchange ratio was lower during the daylight intervention than during the artificial light intervention, indicating that the participants found it easier to switch from using carbohydrates to fat as an energy source when exposed to natural light.
Per1 and Cry1, genes that help control our body clock, were more active in natural than artificial light, the researchers said.
Resting energy expenditure and core body temperature followed similar 24-hour patterns in both light conditions, they said.
Serum insulin levels measured during the MMT were similar in both light conditions, but the pattern of serum glucose and plasma free acids significantly differed between conditions.
The results, particularly the better blood sugar control during the natural light invention, suggest that exposure to natural daylight is beneficial to the metabolism and could help treat and prevent type 2 diabetes and other metabolic conditions, such as obesity, Habets added.