So it’s been a while since I’ve written here, but that’s mostly because as soon as school let out for the summer I’ve been off on adventures of one kind or another. This is the only summer in our med program that we get off, so I’ve been trying to make the most of it.
I’ve noticed that, even as pale as I am, in the sunny weather I still manage to tan (or at least be a darker shade of pale), and it started me thinking back to all we learned about Vitamin D this year.
Vitamin D is an essential nutrient that, among other things, heavily regulates calcium absorption in the intestine. Without vitamin D we would not absorb enough calcium and as a result would have bone health issues from an early age (rickets, etc.), as well as being at a higher risk for autoimmune disease, cancers and cardiovascular disease.
Vitamin D3 (Cholecaliferol)
We primarily synthesize vitamin D from sun exposure: ultraviolet radiation causes a chemical change in a cholesterol derivative (7-dehydrocholesterol, for my chemically inclined readers), creating what we call vitamin D3 (cholecalciferol). D3 is absorbed through the skin and transported in the blood to the liver and finally the kidneys before it is the active form of vitamin D known as calcitriol. Calcitriol acts on the intestines to up-regulate the absorption of dietary calcium, which as you might imagine, is incredibly important for bone health and other metabolic processes.
You can also get some vitamin D from plant sources, but even if a food has been specifically fortified with D, it is difficult to get enough without making your own from sun exposure!
The vitamin D3 that you make on your skin from sun exposure is an oil-soluble molecule which stays in your skin’s natural oil layer before being absorbed. Furthermore, full absorption can take up to 48 hours, and during this time you can lose vitamin D by washing it off your skin (such as scrubbing your body with soap). So use less soap (or don’t soap your whole body - especially those areas that have been exposed to the sun) when you shower to spare some of your vitamin D!