What is Blue Light?


I’m talking with Greg Yeutter today, founder of Bedtime Bulb, and pretty much the guy you want to be talking to about all things light. In our video chat below, Greg explains how a certain type or light, blue light, affects the circadian rhythm of the body AKA the body clock and why we want to limit it during certain times of the day.

Blue light is produced naturally by the sun and artificially by modern light sources such as TVs, phones, computers, and lighting in our homes. When our eyes see this light (also called melanopic) they tell the body clock that it’s day time. This, of course, is the right signal to send to the body when it is, in fact, day time. This is why you want to get outside and get natural light from the sun during the day. The issue is when we are exposed to this blue light when it is no longer day time and the body gets the wrong message, which messes us the circadian rhythm and other hormonal actions that rely on this. 

What is Blue Light’s Impact on the Body?

TWhen we are exposed to blue (melanopic) light in the evening and well into the night by looking at our phones, having ceiling lights on in the home, watching TV, staying up and reading on a tablet, etc., that when this becomes an issue. This exposure to blue light into the night hours confuses the body by sending the day time signal at night which can impact sleep cycles, hormones regulation, and digestion.

The image on the left shows the typical light wavelengths during the daylight. Compare this with the image on the right which shows the light wavelengths emitted from Bedtime Bulb. The gray curve is the area that is interrupted by blue and green melanopic light. You can see that daylight has a lot of blue/green, while Bedtime Bulb doesn’t have much.

How Blue Light Impacts Your Hormones

Before modern times, we really didn’t have much of a choice when it came to manipulating our circadian rhythm: when the sun was up it meant we were too and that’s when work got done. Then when the sun went down it was bedtime. Ah, simpler times, right?

This ensured a simple way to get blue light during the day and eliminate it at night. In today’s world not only do we get more blue light at night from artificial light sources, we often get less blue light during the day too because many of us are sitting in an office all day. Off-rhythm light exposure results in both a weaker and a delayed circadian rhythm that encourages late bedtimes and makes getting up the morning tough. In fact, women with PCOS already have a delayed circadian rhythm so find it super difficult to get to bed at a decent time and wake up early. 

PCOS means lower estrogen levels and poorly functioning estrogen receptors so the circadian rhythm is harder to establish. That’s why women with PCOS like to stay up late, wake up tired, and aren’t hungry for breakfast but get famished later in the day. 

Approximately one-third of all the genes in the human body are regulated by the circadian rhythm. These are called clock genes. This is why living off the beat with the circadian rhythm affects not only sleep and hunger, but it also affects the metabolism of every cell in your body.

Take for example how during the day your liver actually increases in size, produces more digestive enzymes, proteins, and bile and then at night reduces in size and quiets all function to restore and regenerate. Hormones like cortisol, ghrelin, leptin, and insulin are all in flux throughout the day in order to wake you up, digest your food, and manage blood sugar and then go into a mini hibernation at night.

When this coordinated process becomes unsynced, your health suffers. If you produce stomach acid on an empty stomach you get heartburn – if the intestines move too fast you get diarrhea or too slowly you get constipated – if the liver is poorly timed fatty liver develops – and if your hunger and satiety hormones are off you overeat, gain weight, and develop insulin resistance.

This is why staying up too late can make you sick. And conversely, why simple changes like having exposure to morning sunlight and limiting exposure to blue light at night can make you healthy.

Do Blue Light Blocking Glasses Actually Work?

I really wanted to ask Greg about blue light blocking glasses and if they actually live up to their hype. If you haven’t heard of these glasses they are marketed to limit blue light exposure and come in all cute styles and shapes and are touted by brands like Warby Parker. The blue light “upgrade” is always an option on pretty much any online glasses store out there. But does this function actually work?

I had always read that these blue light glasses only work if they have the orange/red lenses in them. So what’s with all of these clear lenses that claim to be blue light blocking?

First of all, Greg explains that “blue light blocking glasses are a decent option, especially if you’re traveling a lot. But a lot of the marketing claims are overstated, particularly when they are sold as an add-on coating to regular eye wear.”

I knew it!

He goes on to explain, “I would not waste your money on blue light blocking lenses that are clear or only faintly yellow in color, as these barely reduce any blue light at all. You may consider purchasing glasses that are deep yellow, orange, or red in color. All of these significantly reduce melanopic light.Deep yellow is probably the most practical and my recommendation, but deep orange or red will cut out nearly 100% of melanopic light.”


Sorry beautiful glasses model, looks like in order to actually get the benefits of blue light blocking glasses you have to wear something akin to these sexy orange tinted glasses!

How to Limit Blue Light

The best part of taking measures to reset your circadian rhythm is, it’s super easy! Thankfully Greg goes onto explain three easy ways to limit blue light exposure when we don’t want it:

  1. The number one thing is to get outside in the morning or early afternoon whenever possible to get that daytime blue light input
  2. Second, starting around dinner time, try to reduce the brightness of your lighting and electronic devices to the lowest comfortable level. This is also where Bedtime Bulb can be super handy. Simply replace your bedside table light or your floor lamp bulb with Bedtime Bulb to get the same benefits of other dimming options for your lighting, without needing anything fancy.
  3. Third, if available, you should use a night mode on your electronics, such as f.lux (for Android) or Night Shift (for i.Phone).

As I mentioned in the video, I use Bedtime Bulb and absolutely love it. I have used it in my bedside table light for years and just ordered a new one to put into my floor lamp by my couch as that’s usually the last light we have on at night. Bedtime Bulb has been selling on Amazon for a year and a half now, and it’s actually the top-selling, highest-ranked product in the category.  I definitely notice a difference in the intensity of the light overall, which helps to communicate to the body a “nighttime” message instead of a “daytime” one. 

Affiliate Disclaimer: This post may contain affiliate links which means, to no extra cost to you, I would make a small fee if you use them.