Grab your sunglasses and get ready for plenty of ice cream because it’s finally summer! The warm sun calls everyone to come outside and enjoy the sunshine. Everyone generally seems happier during this season. Perhaps because there’s no more school for three months? Maybe just the thought of having an excuse to eat ice cream every day is enough for you to smile. Or could it be that since we’re all warm-blooded mammals, we enjoy the continual warmth? Those could all be reasons, but I will focus more on the “biological basis and behavior” perspective.
Would you believe it if I told you that the longer you’re out in the sun this summer, the healthier you’ll be for the winter?
If you do, great, because you’re correct! Two interconnectable reasons for why I make this claim: sunshine allows for our bodies to produce more cholecalciferol (C27H44O), or commonly known as vitamin D, and serotonin (C10H12N2O, or 5-hydroxytryptamine), a neurotransmitter that regulates our mood and even contributes to happiness (1). The more we become exposed to sunshine, the more vitamin D we accumulate into our metaphorical storage that will be used during the fall and the winter (1). Vitamin D also spurs the production of serotonin, so our mood remains stable (5).
Our mood is dictated by two chemicals: serotonin and melatonin (C13H16N2O2, or N-acetyl-5-methoxy tryptamine). Unlike serotonin, melatonin is a hormone that regulates sleep. Furthermore, serotonin and melatonin have an inversely proportional relationship with brightness; therefore, when we are in bright settings, our serotonin level increases while our melatonin level decreases (1). This relationship confirms why we are happier with more exposure to the sun since our body becomes more alert with the low melatonin level and increase in happiness due to a high serotonin level.
Vitamin D also contributes to our mood. Different from the serotonin-melatonin relationship, vitamin D has a directly proportional relationship with serotonin guided by brightness, so it helps maintain a healthy production of serotonin from the brain (3). But that’s not what vitamin D only offers; it is an essential vitamin (duh) that mainly helps our bodies build stronger bones through calcium absorption (6).
“Kenny, what happens if we have a lack of serotonin or vitamin D?”
Excellent question, audience! Well, if sunshine boosts our happiness, could there be a chance that a lack of sunlight on our bodies lead to depression? The answer, again, is yes.
This depression is called seasonal affective disorder (SAD; no pun intended). Someone can feel perfectly fine during the spring and summer then suddenly enter an intense depression starting late fall or early winter. That is someone with SAD. This clinical depression is prevalent in places with very little winter daylight such as Alaska (3). In other words, SAD takes place on people who lack sun exposure. Now here’s the major question: Is it because of a lack of serotonin or vitamin D?
Researchers have yet to discover the true effect(s) of seasonal affective disorder. What they do know is that a lack in either serotonin or vitamin D have strong correlations to this disorder, and people tend to have SAD during the winter (3,5). This may be the case since serotonin level is lowest during the winter, further confirming the correlation of serotonin and SAD (2). Perhaps even an increase in melatonin level due to the dark winter can disrupt our circadian rhythm, which supposedly can affect our mood as well (3,4).
That’s not the only problem with a lack of sun exposure. Since your body won’t produce as much vitamin D as well, you will be prone to vitamin D deficiency, meaning weaker bones, infertility, general poor health, and many kinds of cancer: prostate, colon, and, ironically, skin.
So make arrangements to go out in the sun! Make sure to have at least 15 minutes of unprotected sun exposure three times a week, as sunscreen blocks the ultraviolet rays which will hinder vitamin D production. After all, this time of year should be a very fun and restful break (assuming you are granted this luxury of a three month break; sorry full-year workers). So, what are you waiting for, go out and enjoy the sunshine!