The Sunshine Vitamin

Vitamin D is one of the essential vitamins, meaning it is required for the body to work properly. So we have decided to break down some of the basics of vitamin D, what it is, what it does and how to get it. While it would be impossible to be completely exhaustive of the massive volume of research on vitamin D we will be as accurate as we can. 

Vitamin D is a steroid hormone that can be produced in the body. A hormone is a signaling molecule that stimulates distant tissues to regulate body processes. They act in all corners of the body and have deeply complex mechanisms of action. Vitamin D in particular helps to regulate the expression of over 1,000 different genes. The primary source of vitamin D is from the skin. However, it does require UVB exposure which comes from sunlight. UVB converts a precursor chemical found in the skin into vitamin D. This means that sun exposure is directly needed for the production of vitamin D. This also means that using sunscreen can decrease the amount of vitamin D produced in the skin. It is not a large decrease, although the research was done on sunscreens with relatively low SPF, so it is unclear if a high SPF sunscreen would have a larger impact. Since sunlight is required for the production of vitamin D, anything that diminishes the exposure to it can negatively impact vitamin D production. Things such as living in northern latitudes and spending excessive time indoors can decrease the overall production of vitamin D. Age also has an impact on the skin's ability to produce enough vitamin D. An individual in their seventies produces about 25% of an individual in their twenties. Vitamin D is also a fat soluble vitamin, meaning it dissolves in and is stored in fat. This leads to individuals having more body fat having lower levels since more of the vitamin is being stored and less is available in the bloodstream. 

On the broadscale, vitamin D plays a role in calcium balance, bone health, blood pressure regulation, immune function, and aging, along with other physiological processes. In regards to calcium balance and bone health, the primary function of vitamin D is to stimulate absorption of calcium from the GI tract. In regards to immune function, vitamin D supplementation can decrease the rates of influenza A infection. For cardiovascular health, the inflammatory and immune cells that cause cardiovascular death are actually regulated by vitamin D. It also can help keep arteries flexible which can help control high blood pressure. It has also been seen that men with low levels of vitamin D are at a higher risk of stroke and heart disease than same aged men with higher vitamin D levels.  

Many individuals choose to supplement vitamin D because of a variety of factors like not getting enough sun exposure, living in a northern latitude or any other reason. First and foremost, supplementation should always be done under the supervision of a licensed physician. Research has indicated that in order for vitamin D supplementation to be the most effective, it should be done daily or close to daily. There are two primary forms of vitamin D; D2 and D3. D2 is produced in plants and fungi, while D3 is produced in animals. Most data points to the fact that both can be effective in supplementation, however, some data has started to indicate that D3 might be more effective, but that line of research is still in its infancy, and hard conclusions can not be drawn yet. 

All of this research, when compiled, points us to an important conclusion. Vitamin D is very essential for proper functioning of the body and optimal health. This means most individuals would benefit from regular blood testing to see where their vitamin D levels lie and working with their primary care doctor to make sure they are in the optimal ranges. 

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Wang, Tian-Tian, Luz Elisa Tavera-Mendoza, David Laperriere, Eric Libby, Naomi Burton MacLeod, Yoshihiko Nagai, Veronique Bourdeau, et al.  Large-Scale in Silico and Microarray-Based Identification of Direct 1,25-Dihydroxyvitamin D3 Target Genes  Molecular Endocrinology 19, no. 11 (November 2005): 2685–95. 

Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium A Catharine Ross, Christine L Taylor, Ann L Yaktine, Heather B Del Valle  Dietary Reference Intakes for Calcium and Vitamin D  Washington (DC): National Academies Press (US); 2011.

Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. The American journal of clinical nutrition. 2010 May 1;91(5):1255-60.

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Chao, Yi-Sheng, Ludovic Brunel, Peter Faris, and Paul Veugelers.  The Importance of Dose, Frequency and Duration of Vitamin D Supplementation for Plasma 25-Hydroxyvitamin D  Nutrients 5, no. 10 (October 2013): 4067–78.