Overexposure to light can disrupt the circadian rhythms that regulate many aspects of our health and well-being. A recent study has shown that continuous exposure to bright light and the resultant circadian imbalance can adversely affect bone and muscle health as well. According to the American Medical Association(AMA), excessive amounts of blue or white light are much more harmful than natural light.
Light is essential to life, but today we’ve taken the idea of “let there be light” too literally! We work and play at all hours, blurring the boundary between night and day. Apart from the hours of artificial lighting, we also have laptops, TVs, mobiles, and tablets blinking and blazing. All this overexposure to light can disrupt our internal clock, which in turn has heath implications. It has even been linked to conditions such as diabetes, bipolar disorder, obesity, and depression.1 Now, new research has found that excess exposure to light may harm our bones and muscles as well.
The Effect On Bones And Muscles
A study by Lucassen et al. has shown that overexposure to light and the resultant disruptions to the circadian clock can affect muscle function and bone strength. When mice were exposed to light continuously for 24 weeks, it reduced the rhythmic functioning of the suprachiasmatic nucleus (a group of nerve cells found in the hypothalamus that controls the circadian cycle) by 70 percent. Bone and muscle health took a beating as well – the mice’s grip strength reduced and so did the length of time for which they could hang from a wire or grid. They also showed signs of bone deterioration and the kind of inflammation usually seen in premature aging. The good news is that within two weeks of stopping the constant exposure to light, the suprachiasmatic nucleus recovered and bone and muscle health was restored.2
What Are Circadian Rhythms?
Human life has evolved over millions of years in tandem with the natural rhythms of the earth. Physical, behavioral, and mental changes occur in us in a cyclical manner every 24 hours. These are called circadian rhythms and are found not just in human beings but also in plants, animals, and even microbes. Our biological clocks are made up of groups of molecules that interact with each other across the body, and the “master clock” – the suprachiasmatic nucleus in the brain – makes sure that they’re all synchronized. Circadian rhythms have an impact on many aspects of our health and well-being – for instance, our sleeping patterns, body temperature, the release of hormones like melatonin (which directs our sleep and wake cycles)3 and growth hormone (which directs physical development and growth) are all linked to the circadian rhythms.4. Interestingly, low levels of growth hormone in adults can affect bone strength, muscle mass, and energy levels.5
Although circadian rhythms are controlled by our genes, they also respond to cues from the environment. Light plays a major role here – it is the signal that turns the genes controlling our rhythms on or off.6 Regular exposure to light and darkness is essential for our body to synchronize itself with the outside environment and to stay in good shape. And when we upset this, a host of health implications, including the possibility of bone and muscle deterioration, kick in.
Are Some Kinds Of Light Worse?
According to the American Medical Association, excessive amounts of blue light – the kind that is given out by bright LED lights (which basically appears white to us) – is quite harmful. These LED lamps affect our circadian rhythms five times more than conventional lamps and suppress the production of melatonin the most.7
A Time For Everything
Today, more than 99% of Europe and the US lives under a sky that is polluted by light and more than 33% of the world can no longer see the milky way.8 But as the study we just looked at indicates, reversing the effects of excessive light may be as easy as turning the lights out at the right time. Further research will help to confirm this and better understand how much excessive light can affect us. In the meantime, don’t get carried away by the bright lights – remember, we need a little darkness in our lives too!
References [ + ]
|1, 3.||↑||Circadian Rhythms Fact Sheet, National Institutes Of Health, 2012.|
|2.||↑||Lucassen, Eliane A., Claudia P. Coomans, Maaike van Putten, Suzanne R. de Kreij, Jasper HLT van Genugten, Robbert PM Sutorius, Karien E. de Rooij et al. “Environmental 24-hr Cycles Are Essential for Health.” Current Biology 26, no. 14 (2016): 1843-1853.|
|4.||↑||Albert, Richard K. The Merck manual home health handbook. Edited by Robert S. Porter, Justin L. Kaplan, and Barbara P. Homeier. Merck & Company, 2009.|
|5.||↑||Growth hormone test, National Institutes of Health.2014.|
|6.||↑||Circadian Rhythms Fact Sheet, National Institutes Of Health, 2012.|
|7.||↑||AMA Adopts Community Guidance to Reduce the Harmful Human and Environmental Effects of High Intensity Street Lighting, American Medical Association.|
|8.||↑||Falchi, Fabio, Pierantonio Cinzano, Dan Duriscoe, Christopher CM Kyba, Christopher D. Elvidge, Kimberly Baugh, Boris A. Portnov, Nataliya A. Rybnikova, and Riccardo Furgoni. “The new world atlas of artificial night sky brightness.” Science Advances 2, no. 6 (2016): e1600377.|