Light & Sleep Influence Disease


A recent article put out by Harvard Health, titled “Blue light has a dark side,” reminded me to pull out some studies I saved on this topic. You may know the sun spits out a spectrum of colors (wavelengths). The blue spectrum enters the eye and sends signals to the suprachiasmatic nucleus in the brain, which sets our biological clock.
As you can see by the graph, blue light greatly suppresses melatonin synthesis – it hardly lifts off the x-axis! [1] This makes sense. We don’t want melatonin synthesis during the day. However, this can be a problem because artificial light – which we’re exposed to at night – contains blue spectrum. If up till midnight, we could be suppressing melatonin ~6 hours past its normal starting point! Can you imagine if we suppressed other hormones that long? This is a precursor to disease that many physicians don’t consider.
For millions of years our ancestors were exposed to blue light from sunrise to sunset, but none at night (fire has no blue spectrum) to allow melatonin synthesis. We now spend our nights with light bulbs, TV, cellphones and computers. Why does this matter?
Melatonin and sleep have major influences on metabolism. There’s evidence that melatonin facilitates growth hormone secretion, suppresses cancer growth and much more [2,3] Meta-analyses—the strongest form of scientific evidence—find that poor sleep is one of the strongest risk factors for heart disease, type II diabetes, depression and **obesity**. [4,5,6,7] So what can you do?
a)Keep the lights as dim as you can tolerate at night or use natural lighting, such as candles.
b)Download the Flux software/app for your computer and phone (blocks blue light)
c)Blue light blocking glasses. As you can see from the graph, these glasses allow melatonin synthesis. You may have seen these on Brad Pitt and other celebrities.

3.PMCID: PMC4233441
5.doi: 10.2337/dc09-1124
6.PMID: 23814343
7.PMCID: PMC2398753