A collaboration between researchers in Strasbourg, France and Amsterdam, Netherlands has revealed that one hour of nocturnal artificial blue light induces an increase of sucrose intake and decrease in plasma insulin concentration in rats.

The study evaluated the acute effects of blue artificial light at night on glucose metabolism and food intake in diurnal rats of both sexes, fed either regular chow or a high-fat high-sucrose diet. After researchers gave a one-hour blue light pulse, they administered an oral glucose tolerance test. One week later, the rats received a second light pulse, and food intake was evaluated in both diet groups every 12 hours, the day before and the day after the light exposure. The rats received a third light pulse a week later, and researchers took blood samples to analyze glucose, insulin and corticosterone levels.

In chow-fed rats, the glucose tolerance test results were significantly higher for those of both sexes exposed to blue light compared with those not exposed to the blue light. This was also observed in males, but not females, fed the high-fat, high-sucrose diet.

Researchers believe that these findings could possibly indicate the harmful effects regarding human artificial blue light exposure from devices and screens.