It is exciting to learn what scientists are newly discovering about the importance of getting outside every day to soak up some sunshine. We all know about the body’s need for ultraviolet radiation from the sun for Vitamin D production, but how the rest of the light spectrum (discussed below) affects our bodies is truly amazing! In addition, the fact that morning light is important for helping set our circadian rhythm, or internal master body clock, will be critical to remember as we explore further our bodies need for sunshine.
Perhaps we all think of light only as something needed to perform our daily activities or enabling us to see in the darkness. In fact, beyond this basic use, light is critical to our healthy cellular function and indeed our immunity and overall health. Almost all the cells (the microscopic structural unit) of our bodies contain mitochondria. These mitochondria may be thought of like the “engine” of a car which are responsible for producing the power or energy for the cell to function. Within each cell there is a conversion process of the food we have eaten – carbohydrates, fats and proteins – into the chemical energy, or ATP (adenosine triphosphate) which can be used by our bodies. A natural byproduct of this process is oxidative stress where free radicals, or reactive oxygen species (ROS) are produced. This oxidative stress is like the normal heat produced by an engine. In a car, overheating of the engine may occur when the car has not been well maintained for example, or if any of the mechanisms in place to keep the engine cool are inadequate or malfunctioning. When the heat builds up in the car, then there is overheating. Similarly in the cell, when there is too much oxidative stress the cell cannot function properly, and you get less optimal health. Inflammation, diabetes, dementia and cancer have all been linked to this excess oxidative stress and the resulting mitochondrial dysfunction.
One of the important mechanisms in place to reduce excessive oxidative stress within each cell occurs during our sleep every evening. Melatonin, which is one of the strongest known antioxidants, is released at night from the pineal gland into the blood circulation. This melatonin is our signal for sleep. In addition, reaching each cell through the bloodstream, melatonin enters the mitochondria and can help clean up those reactive molecules (ROS) and thereby combat excessive oxidative stress. However, because these byproducts of energy metabolism are highly reactive and can cause damage immediately within the cell, this potential oxidative stress must be addressed throughout the daytime as well.
Now the fascinating point with sunshine is that although melatonin secretion by the pineal gland is shut down when light enters the human eye, there is a completely different system which is hypothesized to operate during the day. This is where sunshine enters the picture. Infrared radiation (not visible to the human eye) from the sun enables mitochondria to produce melatonin on-site at the cellular level and thus, acting as a potent antioxidant protect mitochondria from oxidative stress. This melatonin cannot be from a melatonin supplement taken by mouth, but rather from the sun’s energy penetrating the body’s tissues and interacting at the cellular level within the mitochondria. Interestingly, this intracellular melatonin doesn’t enter our blood circulation and cause us to feel sleepy during the day, as would the melatonin released in the evening from the pineal gland.
If we look more closely at the full spectrum of energy or radiation from the sun, only 39% is visible light and 7% is ultraviolet radiation (important for Vitamin D production). That leaves 54% of the sun’s energy radiating in the infrared spectrum which is not visible to the human eye. This energy is perceived as heat and can penetrate the layers of the skin and even more deeply into the tissues of the body. Scientists estimate infrared radiation penetration to be one to eight centimeters in depth, even penetrating our clothes and bone tissue. We also don’t need to be in direct sunlight as the natural environment, such as trees, reflect this infrared radiation to our bodies, even on overcast days. Thus, spending time outside in sunshine & green spaces is important to reduce the oxidative burden of our cells and enable our “engines” to function optimally. Oxidative stress and the resulting mitochondrial dysfunction are linked to many chronic diseases. We want our mitochondria, those cellular powerhouses of energy production to function optimally for our bodies’ health.
Even in past centuries, like the late 1870s, respiratory illnesses like tuberculosis were treated with sunshine in sanatoriums. Hospitals were built with solariums where patients could lay outside in the sun. We know globally influenza cases peak during winter months and in fact higher pneumonia complication rates have been found to be directly linked to higher latitudes. The higher the latitude, the further away from the equator or farther north one would be with less duration of sunshine. More recently research has shown increased Covid morbidity & mortality in a similar pattern of higher latitude countries. However, this effect is modified by greater prevalence of obesity within a country such as seen in Central and South America. It is widely understood that oxidative stress is at the core of severe Covid-19, requiring antioxidants to neutralize the ROS.
Incorporating being outside into a daily routine can easily boost one’s overall health and longevity. That intracellular melatonin is formed in response to sunshine, counter-acting the accumulation of free radicals and thereby reducing oxidative stress, should encourage everyone to get outside and enjoy the sunshine, of course with proper sun protection to prevent skin damage! Everyone, tune-up your engines !
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