Conway McLean, DPM, Journal columnist

The news these days can be particularly gloomy, what with the talk of pandemics, climate change, and the world economy on shaky ground. The times can be downright depressing to those well-read on the affairs of the world. Gathering with friends and family is no longer a tonic for loneliness or depression. One easy recommendation is to get outside and “catch some rays”. This phrase refers to getting sun exposure, recognized universally as a mood enhancer, certainly a positive attribute in this age of emotional and financial stress.

Perhaps the mood-boosting benefits of sunlight are due to the recognition of all the health benefits that go with it. In certain ancient cultures, the god of medicine was Apollo, who also happened to be the deity of sun and light. Current scientific thinking has a similarly schizophrenic view. Exposure to the sun, more specifically ultraviolet radiation, has both beneficial and deleterious effects on health.

Our emotional well-being is enhanced by getting time in the sun, which happens through several mechanisms. For example, sunlight helps boost an important brain chemical called serotonin. This naturally-occurring neurotransmitter gives you more energy and helps keep you calm, positive, and focused. Consequently, those individuals suffering from seasonal affective disorder (SAD) linked to low serotonin are sometimes treated with light “therapy”. The production of both melatonin and serotonin are tied to sun exposure. Serotonin is converted into melatonin in response to the day-night cycle. And melatonin has many important attributes, improving our ability to fight infection, control inflammation, and regulate our auto-immunity.

Of the many benefits to health, perhaps the most well-known attribute of sunlight is in the production of vitamin D, also known as “the sunshine vitamin.” Unlike certain essential vitamins, which must be obtained from food, vitamin D can be synthesized in the skin through a photosynthetic reaction triggered by exposure to sunlight, specifically ultraviolet radiation-type B (as opposed to UV-A, which seems to have a strong aging effect).

Vitamin D is a crucial ingredient for overall health, protecting against inflammation, lowering high blood pressure, aiding in muscle health, even improving brain function. The sun’s UV rays help your body make this required nutrient. D is important for strong bones and blood cells, as well as an effective immune system. It also helps you take in and use certain critically important minerals, like calcium and phosphorus. And while most people get enough vitamin D from food, children with insufficient levels get rickets (with other potential risks), a disease leading to soft, weakened bones.

Although the evidence is not definitive, we know several things about sun exposure. It seems exposure to morning light helps to keep fat off. Studies indicate getting 20 to 30 minutes between 8 a.m. and noon, helps reduce fat deposition. Also, moderate amounts of sun in your teen and young adult years seem to make you less likely to become nearsightedness in later years.

This is not meant to be a treatise on skin protection and its importance to health. We know definitively the relationship between excessive sun exposure and the risk of cancer. Too much time in the sun is bad for you. It’s important to use sun protection. But it is now obvious sunshine is beneficial to well-being. Another example: regular, small amounts of UV light help with some common skin conditions, like eczema, psoriasis and vitiligo.

Although skin cancer is associated with too much UV radiation, other cancers seem to result from too little.

Living at higher latitudes, where there is less sun exposure, increases the risk of dying from Hodgkin lymphoma, as well as breast, ovarian, colon, pancreatic, prostate, and other cancers. Ruling out all other variables is difficult, but the evidence points to an important role for sunlight in protecting against cancer.

As mentioned, the relationship between sunlight and vitamin D is an important one. Studies have linked low levels of vitamin D to various diseases, raising the possibility that insufficient vitamin D levels are contributing to many major illnesses. More examples: strong evidence demonstrates high levels of D reduces the risk of multiple sclerosis.

Studies have revealed an association between sufficient vitamin D intake in early childhood with a reduced risk of developing type 1 diabetes. In addition, it appears to reduce the activity of a hormone that tends to increase blood pressure. The muscles in blood vessels have a receptor for vitamin D, which causes relaxation of the muscle. These are the types of cells in the heart, suggesting many mechanisms by which vitamin D may be cardioprotective.

Historically, we have not always appreciated the relationship of sun exposure to health. In the 1600’s, people in the northern climes were covering their entire body and, consequently, many children living in industrialized cities of northern Europe developed rickets. By the late 1800s, approximately 90% of all children living in these regions had some manifestations of the disease.

Attitudes toward sun exposure underwent a radical shift as we learned more about the sun’s ability to fight rickets and TB. In Western societies, the suntan became highly desirable as a status symbol, signifying both health and wealth. After all, only those sufficiently affluent could vacation by the sea or spend abundant time outdoors. Phototherapy became a popular treatment for TB, various rheumatic disorders, diabetes, gout, and chronic ulcers. The tan (healthy) was in, and pale skin (sickly) was out.

So how much sunlight do you need to be healthy? The answer depends on many factors, especially your skin tone, age, health history, diet, even where you live. Current standards claim 5 to 15 minutes is about right to get the most benefit, without risk. How well our skin manufactures vitamin D from the light it receives is reduced by clothing, sunscreen, as well as excess body fat. The distribution of the skin pigment melanin, genetically determined, is also a factor. The greater the degree of pigmentation, the more time in the sun required to produce the same amount of vitamin D.

Unfortunately, there is little agreement on the desired vitamin D levels. Most experts define a deficiency as levels lower than 20 ng/mL. Others assert that levels less than 29 ng/mL should be considered insufficient. According to these figures, an estimated 1 billion people worldwide now have a vitamin D deficiency. Experts believe maintaining a serum level of 55-60 could cut in half the risks of many cancers. And this is easy to achieve: consume about 2,000 IU/day of vitamin D3 (at a cost of less than $20 per year) and spend a few minutes outdoors, 3-15 minutes for lighter complected individuals. Without that time in the sun, they recommend 4,000 IU of vitamin D3.

Scientists worry that the emphasis on preventing skin cancers has obscured the much larger mortality burden posed by more life-threatening cancers such as lung, colon, and breast cancers. Cancer-related death rates decline as one moves toward the lower latitudes providing further evidence of the benefits of sun exposure. In fact, raising vitamin D levels is probably the most important action we could take to reduce the incidence of cancer in North America and Europe, second only to smoking cessation.

Being outdoors is a good tonic for many ailments. As we have learned, sunshine results in enhanced vitamin D production. And, you have to admit, the sun is a reliable mood enhancer. For some, the thought process is simple: they want to look good and healthy. Indeed, most agree a nice tan does just that. But what should be valued are the health attributes of sun exposure, from an improved immune system, healthier blood vessels, even a lessened risk of cancer. Your prescription for sun exposure is now added to that of physical movement. The answer is simple, and I’m not being flippant when I say “Take a hike!”

Editor’s note: Dr. Conway McLean is a physician practicing foot and ankle medicine in the Upper Peninsula, with a move of his Marquette office to the downtown area. McLean has lectured internationally on wound care and surgery, being double board certified in surgery, and also in wound care. He has a sub-specialty in foot-ankle orthotics. Dr. McLean welcomes questions or comments at drcmclean@outlook.com.