A Certain Kind of
Light Contributes to Cancer Risk
October 18th, 2015 by Holly Cornish
What do you see when you look around your living room after dinner?
Chances are, the evening hours find you in a comfortable, well-lit scene that includes some sort of screen that emits light – the screen on a cellphone, tablet, TV set or other video device.
And although you feel relaxed in that snug setting, parts of your body may be reacting to it in ways that threaten your health.
The problem is, while our technological marvels allow us to entertain ourselves at night by watching TV or gazing at other screens, on a molecular level our cells are not enjoying the late-night lifestyle at all.
In fact, it can do some nasty things to your health. . .
Special Message From Lee Euler, Editor
Not so long ago the only light available to humans was natural light – sunlight during the day and, at night, moonlight, starlight and the dim, flickering flames of a fire.
All of that changed during the last 150 years or so when gaslights and electric lights became available. And today, of course, we have access to as much light as we want around the clock.
This is a case of too much of a good thing.
After thousands of years of nothing but natural light, the human body is not well-equipped to function in a world that is lit up 24/7. The body’s built-in cycles and structures are configured to synchronize with a 24 hour period of alternating light and darkness – what’s called the circadian rhythm.
The worst kind of light is this color
Bright light at night disturbs that rhythm and confuses our physiology. And what’s worse, much of the light we’re exposed to in our homes is blue light – the same part of the light spectrum that comes down from the sky during the day. Blue light consists of wavelengths that make the body believe it’s still daylight outside.
Our cellphones, video screens and energy-efficient bulbs tend to flood our eyes with blue light.
The most obvious problem with this circadian confusion is that it disrupts your ability to fall asleep. But beyond that, research connects this late night blue light with a boost in your risk for cancer, heart problems, diabetes and weight gain.1
Your eyes know what time it is
When blue light enters your eyes, it interacts with receptors in the retina that are supposed to help the body recognize the time of day. These specialized receptors are called photoreceptive retinal ganglion cells. They contain a substance called melanopsin that reacts with the wavelengths of light that we see as the color blue.
The reaction communicates with a specific part of the brain that acts as the body’s primary circadian clock.
So when these receptors in the retina are stimulated by blue light at night, the body starts to receive mixed signals. Feelings of fatigue tell us that it’s time to climb into bed. But even as we’re feeling tired, the blue light can cancel out the release of an important hormone the body needs to help it fall asleep – melatonin.
Melatonin, secreted by the pineal gland, is also a central player in regulating your circadian rhythms. In addition, it functions as a powerful antioxidant that helps the immune system fight off cancer and takes part in protecting the cardiovascular system.
As you age, your production of melatonin slows down. Add in too much blue light at night and your melatonin supply dwindles even further, allowing your cancer risk to significantly climb.
We’ve warned in previous issues about the dangers of light at night, and the resulting disruption to your melatonin levels. You might want to check out Issue #420 for additional facts about this important problem.
Research at the Harvard School of Public Health shows that when a man’s level of melatonin drops for an extended period of time it exposes him to a greater chance of suffering prostate cancer.2
“… Health problems associated with low melatonin, disrupted sleep, and/or disruption of the circadian rhythm are broad, including a potential risk factor for cancer,” says researcher Sarah C. Markt. “We found that men who had higher levels of melatonin had a 75 percent reduced risk for developing advanced prostate cancer compared with men who had lower levels of melatonin.”
The Harvard scientists note that other research shows that, in women, this type of reduction in melatonin affects the function of related hormones in ways that increase the risk for breast cancer.
When your circadian rhythms are thrown off-kilter by late night blue light and other factors, you may also become more susceptible to skin cancer and the aging effects of ultraviolet light from the sun.
Research at the Center for Genomic Regulation in Spain demonstrates that skin cells behave differently at different times of the day. Those varying molecular reactions, some of which are designed to maintain skin health, depend on the proper function of the cells’ biological clocks.
When the sun is up, these chrono-biological processes are supposed to turn on genes that are necessary for the cells to protect themselves against DNA damage that can be caused by sunlight.
“Our study shows that human skin stem cells possess an internal clock that allows them to very accurately know the time of day and helps them know when it is best to perform the correct function,” says researcher Salvador Aznar Benitah, who is now with the Institute for Research in Biomedicine in Barcelona. “This is important because it seems that tissues need an accurate internal clock to remain healthy.”
Prof. Benitah’s study shows that when they function properly, the protective genes in skin cells are most vigilant during daylight hours when skin cells reproduce. During cellular reproduction, as the cells divide, they duplicate their DNA, a process that makes their genetic material much more vulnerable to injury from ultraviolet light.
When your circadian rhythm is properly synchronized, these protective genes intervene to prevent genetic damage that can be linked to skin cancer. If they fail to perform their tasks, the DNA is relatively defenseless.
And even if a disrupted circadian rhythm doesn’t lead to skin cancer, Prof. Benitah’s work shows it makes the stem cells in your skin age prematurely, rendering your skin less able to regenerate new tissue. That leads to older looking skin.3
Protect yourself from blue light at night
The easiest way to protect yourself from the harmful effects of blue light in the evening would be to simply turn off all your video devices at sunset – including your cellphone – and switch off fluorescent bulbs which emit heavy doses of blue light.
But few of us are ready to completely give up our night life in that way.
So consider these other measures you can take to protect yourself from the harmful effects of blue light in the evening:
- During the day, get outside in the sunlight as much as you can to help your inner circadian biological clocks stay on track. Exposure to the sun’s ultraviolet light during the day helps alleviate daytime sleepiness, boosts your body’s production of melatonin at night and can make it easier to fall asleep at bedtime.
- If you use night lights when you go to bed, use red bulbs that are as dim as possible. The wavelengths in red light are the least likely to alter your circadian rhythms and distort your production of melatonin.
- At least two hours before you go to bed, turn off your devices that have screens. If you have to view a screen close to bedtime, keep it dimly lit.
- If you consistently work at night or have to view video screens, use glasses that block blue light.
Heed the warnings of researchers who are studying the effects of nighttime light:
“It’s become clear that typical lighting is affecting our physiology,” says Richard Stevens, who performs research at the University of Connecticut. “It doesn’t mean you have to turn all the lights off at eight every night, it just means if you have a choice between an e-reader and a book, the book is less disruptive to your body clock. At night, the better, more circadian-friendly light is dimmer and, believe it or not, redder, like an incandescent bulb.”
And, in other news, PepsiCo, Inc. finally removed aspartame from Diet Pepsi. Problem solved? Not quite. If you missed this story in our last issue, you can read it now below.