Blue light exposure may increase your desire for sweet foods according to a new animal study. Add it to the list of reasons to put your phone down before bed or at least invest in some blue light glasses.

Isadora Baum
July 19, 2019

Photo: Shutterstock

If you're digging into the candy bowl and also checking Instagram or watching TV before bed, your screen may making you up your sugar intake. Blue light-the type that comes from screens-may impact your sweet tooth if you're exposed right before falling asleep. We've known for awhile that too much screen time before bed may disturb your sleep, but new research done in animals shows that it may impact our snacking habits as well.

Just one hour of exposure to blue light in the evening raised blood sugar levels and boosted sugar consumption in male rats. The lead researcher and author, Anayanci Masís-Vargas, along with her team from the University of Strasbourg and University of Amsterdam, shared this data earlier this week at the annual conference of the Society for the Study of Ingestive Behavior (SSIB) in Utrecht, Netherlands.

The Research

The team worked with rats, exposing them to blue light at night and then measured their food consumption and glucose tolerance the next day. The rats were diurnal, which means they are awake during the day and go to bed at night, to mimic human behavior patterns (as opposed to nocturnal rats). What did they find? Well, only one hour of blue light exposure at night made the animals less glucose tolerant, which could be a precursor to diabetes (or pre-diabetes).

And to see how the light affected appetite control and which types of foods they were eating the next day, rats were able to choose between a balanced wholesome meal (like their normal rodent food), water, lard, or sugar water. The results? Male rats went for the sugar when they were around blue light emission, and chose healthier options when not.

Is it Legit?

"These fundamental results are important in societal terms if we think in the 'light pollution at night' at which we are exposed in nowadays," Jorge Mendoza, PhD and researcher on this study told EatingWell. There is evidence to believe that there is a correlation between obesity and artificial light at night, based on studies in the past, and most of this type of lighting comes from LED lights and LED screens, all of which emit blue light and increase exposure. Because the retina is so sensitive to blue light emission, it then acts in response by communicating with parts of the brain that regulate appetite regulation. Mendoza and his team are working to figure out the why. "Retina cells are sensitive to blue light. These cells project to your body clock. The body clock, then, distributes light information to the rest of the brain that controls behavior and physiology," Mendoza says about the hypotheses they're working on.

These new findings show that screen use from televisions, smart phones, and more, during the evening hours might promote the tendency to nosh on sugary foods, without being able to process it as efficiently, too. A caveat? There was only one night of testing, so they'd need to see how it affected weight gain, diabetes, and other factors over time by performing this for several nights and creating a pattern.

"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. 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 googles that are already available in the market," Masís-Vargas stated in a press release.

So put down your phone and pick up a book. While the latest study was done on rats and more research is needed, it's probably still a good idea to limit your blue light time at night.

Related:

9 Foods to Help You Sleep

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