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Red is a colour often associated with passion, power, aggression, anger, even fear. Not so, when it comes to your health in body and mind. Scientific research suggests that bathing your body in red light at night could help you sleep better, and reduce your risk of chronic disease. – Marika Sboros
By Marika Sboros
What image springs to mind when you think of red light? A traffic light, or a district in Amsterdam, with prostitutes parading their wares in windows?
US scientists have another vision altogether. They say red light at night is more beneficial for your health than commonly used blue or white lighting; and the more time you bathe your body in red light, the better.
A study by US neuroscientists at Ohio State University, published in the Journal of Neuroscience, builds on a growing body of research on the health hazards of light at night, and shows that it’s the colour of the light that matters most.
And while red is a colour more often associated with power, passion, aggression, anger and even fear, the study shows that red light at night has benefits for both mind and body.
The scientists looked at the effects of a range of different coloured lights on adult female Siberian hamsters. Results showed that blue light — the kind emitted by electronics and energy-efficient light bulbs — had the worst effects on the rodents’ moods, followed closely by white light.
Hamsters exposed to red light at night fared much better. They had significantly less depression-like symptoms, and changes in the brain linked to depression. They slept better. The only rodents that fared best of all, were those who spent the night in total darkness.
The findings could have relevance for humans, particularly those whose work on night shifts makes them susceptible to mood disorders, Dr Randy Nelson, co-author of the study and professor of neuroscience and psychology at The Ohio State University, said in a university press release.
“Our findings suggest that if we could use red light when appropriate for night-shift workers, it may not have some of the negative effects on their health that white light does,” Nelson said.
And while red comes out better than white or blue light, experts say best of all is no artificial light at night. After all, before the industrial revolution, and the introduction of artificial lighting, the sun was the major source of lighting.
People lived according to the rhythm of nature, spending evenings in relative darkness, lightened only by the moon and the stars. They maximised sun exposure by rising early, working outside, and going to bed when the sun went down.
The invention of fluorescent lighting, TV, computers, mobile phones and tablets drastically changed patterns of behaviour by increasing exposure to blue light.
In much of the world, these days, evenings “are illuminated, and we take our easy access to all those lumens pretty much for granted”, say Harvard Medical School researchers, in a recent issue of the Harvard Health Letter.
“We may be paying a price for basking in all that light,” the scientists say.
Curlicue, compact fluorescent light bulbs and energy efficient LED lights produce more blue light than conventional bulbs, the scientists say. Their effects on health are usually enough to offset any benefits from reduced energy bills.
Any light at night will have an effect on the body’s circadian rhythm, and in a worst-case scenario with blue and white light, could contribute to the development of cancer, diabetes, cardiovascular disease and obesity.
Blue wavelengths are beneficial during daylight hours, because they boost attention, reaction times and mood, but may be most disruptive at night, the Harvard scientists say. The proliferation of electronics with screens, and energy-efficient lighting has been increasing people’s exposure to blue wavelengths, especially after sunset, they say.
Scientists don’t know exactly how and why nighttime light exposure can be so bad for health. Research suggests it’s because certain light in the spectrum at night suppresses the secretion of melatonin, a hormone that plays a major role in sleep/wake cycles. Even dim light can interfere with circadian rhythm and melatonin secretion, say scientists.
The Ohio study examined the role of specialised photosensitive cells in the retina, known as ipRGCs. These don’t have a major role in vision, but detect light and send messages to a part of the brain that helps regulate the body’s circadian clock – the body’s master clock that helps determine when you feel sleepy and awake, the scientists say.
Other research suggests these light-sensitive cells also send messages to parts of the brain that play a role in mood and emotion.
“Light at night may result in parts of the brain regulating mood receiving signals during times of the day when they shouldn’t,” said Dr Tracy Bedrosian, a co-author of the Ohio State University study, in a university press release.
“This may be why light at night seems to be linked to depression in some people.”
And while the Ohio study suggests that shift workers could benefit from limiting their light at night from computers, televisions and other electronic devices, and increasing exposure to red light, the researchers say the advice applies to everyone.
“If you need a night light in the bedroom or bathroom, it may be better to have one that gives off red rather than white light,” Bedrosian says.
The Harvard researchers give more tips on healthy light use:
- Avoid looking at bright screens two to three hours before bedtime.
- If you work a night shift, or use a lot of electronic devices at night, consider wearing blue-blocking glasses.
- Expose yourself to lots of bright light during the day. This will boost your ability to sleep at night, as well as your mood and alertness during daylight.
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