Workout Wednesday: Vitamin D – The Sunshine Vitamin

So here is my dilemma: on one hand, we’re told that unprotected sun exposure can cause damage to DNA and increase risk of skin cancer. Some dermatologists are extreme enough to suggest that wearing sunscreen is essential before any amount of sun exposure and that you should avoid exposing your skin to the sun between the hours of 11am and 3pm at all costs. On the other hand, we are told that a certain amount of unprotected sun exposure is extremely beneficial, if not essential, for producing adequate amounts of vitamin D, one of the most important vitamins for the body. What is a person to do in this sticky situation? Become a shadow hermit? Take some extra supplements? I’m not a fan of either idea.
Let’s take a quick detour. So, I think that historical word origins can be pretty cool sometimes. I know that’s kind of nerdy, but I’m ok with it. In the early twentieth century, several scientists began to notice that certain disorders could be prevented or cured simply by eating certain foods. In particular, one scientist noticed that eating polished rice (the pretty rice without the hull) didn’t prevent a neurological disease known as beriberi, but eating unpolished rice (with the hull still attached) would prevent the disease. Obviously there was something special about these rice husks that had to do with preventing the disease. In 1912, Cashmir Funk, a Polish scientist with a really awesome name that sounds like a groovy sweater, found the specific chemical compound in the rice husk that was responsible for preventing beriberi. The compound contained an “amino” group, which is the chemical term for a group with a nitrogen atom attached to three hydrogen atoms (NH3) and it was vital to a healthy life. Therefore, Funk decided to name the compound a “vitamine,” which was later shortened to vitamin [1]. So there we have it: the word vitamin didn’t exist until 1912, and our great-great grandparents had never even heard of the vitamins and the sunscreen that are advertised as being so essential today. Crazy how that works.
But coming back to the topic at hand, vitamins are so named because they are essential to life and must be consumed in the diet; our bodies do not synthesize vitamins themselves. Or do they? The truth is that we simply don’t synthesize adequate amounts of the vitamins that we need, but two vitamins can, in fact, be synthesized in the body. A large amount of our necessary vitamin K is synthesized by gut bacteria, and a large amount of required vitamin D is synthesized from cholesterol compounds in our skin in a reaction that requires UV light. Vitamin D is essential primarily for maintaining the balance of calcium in the body: adequate blood calcium levels are needed for proper neuron function and muscle contraction, but adequate bone calcium levels are needed for the mineralization process that makes our bones solid and not spongy. The bones and the blood exchange calcium, based on the current needs of the body, and vitamin D that facilitates and maintains this balance.
Vitamin D is a fat-soluble vitamin, which means that it can be stored in the body much better than water-soluble vitamins. This makes vitamin D supplementation risky because it is easy to overdose—in fact, vitamin D is the most toxic of all of the fat soluble vitamins. The best way to be sure that you’re getting enough vitamin D is to spend a small amount of time exposed to sunlight each day (without the protection of sunscreen) to facilitate the reaction that makes vitamin D in your skin. People with lighter skin complete this process more quickly than people with darker skin, because darker skin means more melanin, which means more protection from UV rays. Ten minutes with face, legs, and arms exposed is plenty for a fair skinned person to get enough vitamin D on a sunny summer day, but thirty minutes might be required for a person with darker skin to make the same amount of vitamin D with the same amount of skin exposed.
Several factors block the UV rays that are required for the vitamin D making process, including window glass, clothing, sunscreen, and latitude. Yep—latitude. North of 42 degrees latitude, (some sources say Atlanta), there are not enough UV B rays reaching your skin to synthesize vitamin D during the winter from around October to March [2]. That’s a pretty big hunk of the year! So what are some other sources of vitamin D for those months when the sun apparently isn’t going to help us out? Most milk is now fortified with vitamin D, as well as some cereals that are fortified with all sorts of vitamins. Fatty fish such as salmon is also one of the best sources. But vegans take note—plant foods just aren’t good sources of vitamin D, so it’s important for you to get enough exposure to sun when the timing is right!
Although many foods commonly bought at the grocery store are fortified with vitamin D, experts say that it’s still important to allow some sun exposure for adequate vitamin D synthesis. Studies have shown that low vitamin D levels were associated with higher risk of heart disease and colon cancer—yikes! [2].   But what about the risks of sun exposure? It’s all about moderation. Although I am a huge believer in the necessity of sunscreen, I try to remember my great great grandparents who had never even heard of it to remind myself that a few minutes in the sun without sunscreen each day is perfectly OK. For me and my fair skin, just walking from class to class throughout the day is probably enough time to synthesize some vitamin D, but if I’m planning on staying out for a while, the sunscreen is coming with me, and it should be going with you, too!
So go on, wear that tee shirt and those shorts and don’t put your sunscreen on right away if you’re anticipating some quality time in the sun. You’ll be doing yourself a favor by making some Vitamin D; just don’t forget to keep track of time and sunscreen it up after a few minutes. You can always make up for a little lacking Vitamin D with your breakfast cereal, but those corn flakes aren’t going to help you out when it comes to skin cancer [3]. Only you can do that.
Images courtesy of

Workout Wednesday blog posts are written by UNC Campus Recreation staff members. Each Wednesday we swap blog posts with the Tarheel Tone Up blog so that readers can view more diverse post topics that will benefit their health and wellness. Workout Wednesday blog posts can be found both here and on

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