For weeks now, I have been harping on the devastating effects of sunshine – sunburns, skin aging, skin cancer. But, just like any other entity, there are two sides to sunshine. Yes, we all know the bad things that can happen to us if we bake in the sun (or at least we should now know), but don’t we all feel wonderful after being out in the sunlight and enjoying nature? The short answer is of course we do. Sunlight exposure leads to tanning, tanning leads to endorphin release, endorphin release makes happy people, and happy people are, well . . . happy! So there you have it; as much as I wish I could just cover myself head to toe in sunscreen and then black sheets, so that the sun may never touch my skin, I must admit, being outdoors in the sun makes me happy too.
Not only does sunshine provide worldwide happiness, it also provides our bodies with a much-needed vitamin, known as the “sunshine vitamin” or vitamin D. In 1925, Alfred Hess made the observation that, “Light equals vitamin D” (not quite as iconic as E=mc2, but for our purposes it will have to do). Unlike cats and dogs, humans are able to obtain almost 90% of the needed vitamin D through sun exposure (10% of our vitamin D is taken up through our diet). UV radiation is part of a chemical reaction that turns a vitamin D precursor found in our skin into the vitamin D our intestines use to absorb calcium and phosphate in our diets.
Without enough vitamin D in our bodies there are a number of things that start to go wrong. First off, the body’s entire calcium and phosphate balance is majorly disturbed as the intestine cannot absorb these nutrients anymore. Children end up with rickets (skeletal malformation due to vitamin D deficiency, most commonly presenting as bowed legs), adults end up with osteomalacia (“soft bones”) and really old adults end up with osteoporosis (“brittle bones” found especially women over the age of 65, but men are not immune either). These bone disorders, especially in the elderly, result in increased mortality as bones are more likely to break during falls due to the decreased bone mineral density. Therefore, it is recommended that all postmenopausal women take supplemental calcium or dietary vitamin D to ensure their bone structures remain as strong as ever. And going out in the sun every so often doesn’t hurt either.
However, not only does a deficiency in vitamin D result in weaker bones, studies have shown that low levels of vitamin D in the blood may also contribute to premature aging, obesity, worsened cancer outcomes, complications of pregnancy (gestational diabetes, high blood-pressure, low birth-weight infants), and most recently, cardiovascular disease. The media has been focusing on studies showing that increased UV exposure may be a contributing factor to lowering blood pressure and therefore avoiding complications such as strokes, heart attacks or aneurysms. One of the studies, centered in Edinburgh asserted that only vitamin D garnered from sunlight would be sufficient to lower blood pressure as dietary supplements did not seem to have the same effect; they postulated perhaps the immediate benefits of sunlight exposure outweighed the consequences of skin cancer. However, the D-CarDia study, which is a multicenter study across Europe, found that ingesting high amounts of 25-hydroxy-vitamin D resulted in a significant decrease in developing high blood pressure. I personally like the fact that I don’t have to risk skin cancer to decrease my risk of hypertension. In addition to vitamin D dietary supplementation potentially lowering my blood pressure, new research is suggesting that increasing vitamin D exposure may very well decrease the symptoms of eczema (atopic dermatitis), however further research must be done to have firm conclusions.
There you have it, though radiation from the sun may be harmful to one’s skin, there are also many benefits to spending a little time enjoying the sun. Fortunately, no sunscreen completely blocks UV radiation (remember SPF 30 sunscreen only blocks about 97%) and the little that manages to penetrate our manmade barriers is sufficient to allow the conversion of vitamin D precursor to vitamin D in our skin. So, go out, enjoy some sun, get happy, and make some vitamin D; but remember, as with every good thing, enjoy in moderation.
Margit Lai Wun Juhasz
Mount Sinai Medical Student