Nocturnal exposure to light containing short wavelength emissions (450-500 nm) — the kind of light produced by the screens of many devices — raises blood sugar levels and increases sugar intake, according to a study performed on Sudanian grass rats (Arvicanthis ansorgei).
“Much of the artificial light we are exposed to comes from LED lights and screens, which emit high levels of blue light,” said Anayanci Masis-Vargas from the Universities of Strasbourg and Amsterdam and colleagues.
“Retinal cells of the eye are sensitive to this blue light and directly convey information to areas of the brain that regulate appetite.”
In the study, the scientists exposed diurnal Sudanian grass rats to nighttime blue light (490 nm) and measured their food consumption and glucose tolerance the following day.
“In order to better model human light exposure, the rats were diurnal, meaning awake during the day and asleep at night, rather than the typical nocturnal laboratory rats which are awake during nighttime hours,” the researchers explained.
They found that after only one hour of nocturnal blue light exposure, glucose tolerance was altered in male rats, a warning sign of pre-diabetes.
To investigate what happens with appetite control and food choice after exposure to blue light at night, the rats were given the option to choose among a nutritionally balanced food, water, lard, and sugar water.
After the exposure to blue light, the study authors observed that the male animals drank more sugar water that night than during the nights with no blue light exposure.
“Limiting the amount of time that we spend in front of screens at night is, for now, the best measure to protect ourselves from the harmful effects of blue light,” Masis-Vargas said.
“In case it is necessary to be exposed to devices at night, I would recommend the use of apps and night mode features on the devices, which turn the screens more orange and less blue or the use of blue light filtering goggles that are already available in the market.”
Anayanci Masis-Vargas et al. Acute exposure to blue light at night impairs glucose tolerance, alters insulin secretion and increase sugar intake in a diurnal rodent. SSIB 2019, abstract # P37