Light At Night: It’s Messing With Your Glucose Levels, But THIS TYPE Is The Worst

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You’ve probably already heard that watching TV late at night can make it difficult to fall asleep. It’s because our body releases hormones based on light levels. Melatonin, the hormone that regulates our circadian rhythms and gets us ready for sleep, is released at night, but light exposure suppresses melatonin’s release. Light exposure can trick our bodies into thinking it’s time to be up and about instead of heading for dreamland.

But the interruption of our circadian rhythm does more than just rob us of a restful night’s sleep. Late-night light exposure can affect our metabolism, slowing it down and contributing to weight gain and insulin resistance. New research says that not dimming down at night can raise glucose levels and contribute to type 2 diabetes.

But not all light is equally damaging. Blue light, the kind from computers, smartphones, and other electronics, is the biggest metabolic disrupter.

Blue Light Blues

The blue wavelengths of light help us out during the day by boosting attention, mood, and reaction times. The blue light in sunlight has been helping us wake up and get things done during daylight hours since the advent of humankind; it’s only recently that humans have found creative ways to continue light exposure long after sundown. Energy-efficient lighting and the screens of electronic devices expose us to a lot of blue light, and blue light suppresses melatonin more so than other colors.

In a Harvard study comparing the effects of green light to blue light, researches found that blue light pushed back circadian rhythms by twice as long and suppressed melatonin for double the amount of time that green light did. Another study found that if people wore special goggles designed to block blue light, their hormone levels were the same as those exposed to only dim light. Blocking out or avoiding blue light can help us wind down the same way we do when the light is dim.

Blue Light’s Effect on Metabolism and Glucose Levels

Blue light exposure may slow down our metabolisms and contribute to insulin resistance. In a study on adult volunteers, eating while exposed to blue light was associated with higher glucose levels, more insulin resistance, and slower metabolism. Insulin was less able to regulate glucose levels while exposed to bright light in the evening. Over time, high glucose levels contribute to insulin resistance and type 2 diabetes.

According to EndocrinWeb, exposure to light at night can contribute to weight gain even without an increase in calorie consumption. This is because blue light seemed to slow metabolism. People who get more of their light exposure in the morning hours tend to have faster metabolisms.

The exact mechanisms by which these metabolic effects occur are not completely understood, but it is clear that exposure to blue light affects glucose metabolism in the morning and at night. In the morning blue light helps us rev up and get going, but in the evening it seems to throw off our bodies, slow down metabolism, and contribute to chronic disease.

How to limit blue light exposure

Powering down a few hours before bed is the best choice to help your body release melatonin and get ready for a restful night’s sleep. Reading with warmer-toned lights is a perfect pre-sleep ritual, but you may also want to try:

  • Finding dim red lights to use as night lights (red light has the least effect on circadian rhythm).
  • Trying to avoid screens a few hours before bed.
  • Buying special glasses that block blue light.
  • Maximizing your exposure to bright light during daylight hours as this will help you sleep at night.
  • Making your sleeping area as dark and relaxing as possible.
Photo: AdobeStock/leszekglasner

Photo: AdobeStock/leszekglasner


Are you feeling sleepy yet? Our bodies are programmed to rise and rest with the sun, and now that we’re not dependent on the sun to dictate the timeline of our day, our hormones struggle to find their rhythm. The research coming out on the effect of late-night exposure to blue light is a good reminder that just because we can stay up past bedtime doesn’t mean that we should. Take your cue from the sun and know when to shut down!

Stay healthy, friends!

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Katie Taylor started writing in 5th grade and hasn't stopped since. Her favorite place to pen a phrase is in front of her fireplace with a cup of tea, but she's been known to write in parking lots on the backs of old receipts if necessary. She and her husband live cozily in the Pacific Northwest enjoying rainy days and Netflix.
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