Sunlight May Combat Metabolic Syndrome, Prevent Diseases Like Diabetes

Almost every part of our body benefits in some way from the light of the sun and the vitamins that come with it. It keeps our circadian rhythms and sleep cycles in check, gives us vitamin D too keep our energy up and our bodies strong and healthy, and feeds the photoreceptors in our eyes so that we can see the world around us. But did you know that celestial glow could also combat metabolic syndrome and related diseases, such as diabetes?

Until recently, researchers believed that humans and other animals were only able to detect light through their eyes. However, some animals have other light receptors in their bodies, such as frogs, which have special skin cells called chromatophores that can detect light. Rats, similarly, have neuropsin in their skin to help them perceive light so they can maintain their circadian rhythms.

Now, scientists believe that humans may actually have light-detecting proteins called opsins on their fat cells, located in the tissues beneath the skin. Activating this protein by getting plenty of sunlight may help people lose weight and regulate their metabolisms, thereby combatting metabolic syndrome and related conditions.

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“This idea of light penetration into deep tissue is very new, even to many of my scientific colleagues,” says senior study author Richard Lang, Ph.D., from Cincinnati Children’s Hospital Medical Center in Ohio. “But we and others have been finding opsins located in a variety of tissue types. This is still just the beginning of this work.”

Opsins, specifically opsin 3 (OPN3), can be found in several areas of the body, including the brain, testis, liver, and kidneys, as well as in fat cells, also known as adipocytes. Rats and mice have these opsins too, and studies have shown that a specific wavelength of blue light (480 nanometers) from the sun is able to penetrate deep enough into these animals’ bodies to stimulate OPN3 within the adipocytes. Artificial light, on the other hand, is not strong enough to activate these proteins. It is believed that the same may be true of humans.

A growing body of evidence suggests that activating brown adipose fat may protect people against metabolic syndrome, which is an umbrella term that covers conditions such as hypertension, high blood sugar, abnormal blood lipids, and excess body fat around the waist. Metabolic syndrome can be a precursor to other health issues, such as type 2 diabetes, heart attack, and stroke, making it particularly important to understand and fight against.

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The researchers used genetically modified mice that did not have Opn3 coding in their genes to make OPN3. These mice proved unable to burn their brown adipose fat to keep warm in cold temperatures, resulting in lower body temperatures (when exposed to cold) and less fat loss than was seen in normal mice. In another experiment, normal mice were placed in cold environments with a full spectrum of light meant to mimic the sun’s rays. The light stimulated the mice’s OPN3, causing them to burn adipose fat and stay warm. After the 480-nanometer wavelength was shut off, however, the animals’ body temperatures dropped significantly, and they were not able to lose weight when fasting.

Sunlight, therefore, and specifically the blue light of the 480-nanometer wavelength, is believed to be a key to keeping a healthy metabolism. Researchers think this mechanism likely exists in humans as well. They theorize that “insufficient stimulation of the light-OPN3 adipocyte pathway is part of an explanation for the prevalence of metabolic deregulation in industrialized nations where unnatural lighting has become the norm.”

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“If the light-OPN3 adipocyte pathway exists in humans, there are potentially broad implications for human health,” the researchers write. “Our modern lifestyle subjects us to unnatural lighting spectra, exposure to light at night, shift work, and jet lag, all of which result in metabolic disruption.”

If further studies are able to corroborate this data, doctors may soon be able to prescribe light therapy to patients who are at risk of developing metabolic syndrome or to those who already suffer from one or more metabolic conditions.

As Lang puts it, “If people want to take anything personal away from this, you likely can’t go wrong by spending more time outside,” says Lang. Nobody can prove that the researchers’ theory is right, but getting more sunlight is still a good idea and has a plethora of health benefits.

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