The Mystery of Vitamin D

Can one describe a vitamin as mysterious? What about elusive or misunderstood? Well, I'm going to! Vitamin D is a complex and intriguing nutrient. 

We get vitamins from the foods that we eat, and while it's true that some foods contain vitamin D, that's not the whole story. We make most of our vitamin D when we expose our skin to ultraviolet light. It is the only vitamin our body is capable of making. Mysterious, right? But, that's not all, the intrigue continues. The form of vitamin D made under our skin isn't active yet. First it needs to travel to the liver and to the kidneys where it becomes activated. Once it's in an active form, vitamin D starts behaving more like a hormone that a vitamin. Vitamin D travels to cells all over your body and helps them to communicate properly. Researchers are still uncertain exactly how vitamin D influences various conditions and disease states. Elusive, huh?

Here's what we do know about the many functions of activated vitamin D:

  • Regulates your body's level of calcium and phosphorous, essential for the health of your bones and teeth
  • Benefits the immune system
  • Prevents certain types of cancer
  • Influences mood (link between seasonal affective disorder and low levels of vitamin D)
  • Plays a role in proper brain development
  • Contributes to healthy muscle function, including your heart

Now, here's where the plot thickens, most of us are deficient in vitamin D. Although some foods contain vitamin D, (liver, kidney, fish, egg yolks, dark leafy greens and mushrooms), it's difficult to get enough from food alone.


The best way to get enough vitamin D is from sunlight. But here's the catch, there are a number of factors that influence how much of the 'sunshine vitamin' you'll make

  • For those of us who live away from the equator, the UV light isn't strong enough during the winter months. Here in Toronto we can't make vitamin D from about October to April. 
  • The darker your skin tone, the more natural UV protection you have and the longer you need to stay in the sun. (Where someone with fair skin might make enough in 5 minutes of summer sun, it can take over an hour for someone with dark skin.)
  • How much of your skin you expose determines how much vitamin D you'll make. If you only have a bit of bare skin on your arms, you won't be making very much.
  • Once vitamin D is made on your skin, it takes up to 48 hours to be absorbed by your body. So, if you jump in the shower and lather up, you're washing the vitamin D down the drain! (You can rinse with water, but you can't use soap.)
  • Other factors that decrease how much vitamin D we make include aging, sunscreen, cloudy weather and air pollution

Tricky, eh? If you suspect you might be deficient, ask your doctor to test your vitamin D [25(OH)D] levels. The test is no longer free in Canada (it costs $40), but it will provide with the information you'll need to determine if taking a vitamin D supplement is right for you. Work with your natural health care practitioner to determine how much (too much can be toxic) and the best form of vitamin D to take (the D3 form is easier for your body to use than D2). 

Although vitamin D isn't as clear-cut as some of the other vitamins, it is essential for our health so make sure you're getting enough.