Originally published on Kate’s blog
What is vitamin D?
Humans primarily make vitamin D via our skin from exposure to ultraviolet light. Actually, we make cholecalciferol which is converted into fully active vitamin D by our liver and kidneys. Vitamin D influences bone health, blood sugar control, and immune support, as well as several other functions. According to Health Canada, only 1/3 of the population has vitamin D levels above 75 nmol/L, which is the lower level for “sufficiency.”
Why are we deficient?
1. We don’t get naked enough!
Imagine how early humans lived… They wore little clothing and spent most of their time outdoors in warm weather, so they made lots of vitamin D in the summer, which was stored in their bodies and used during the darker winter months. Is this how you live today? I doubt it! Most of us spend most if not all our time indoors and when we are outdoors we cover up. All of this means we make little to no vitamin D at all from the sun.
2. We can’t eat enough vitamin D!
Unlike most other nutrients, there are few foods that provide vitamin D. Because we mostly get vitamin D via the sun, food is really just a back-up support system in this case. The World’s Healthiest Foods website only lists 6 foods as sources of vitamin D: Salmon, Sardines, Tuna, Cow’s milk, Eggs, Shiitake mushrooms
3. Other circumstances
There are several other factors that impact vitamin D levels: Season, Latitude, Age, Medications, Skin pigmentation
The test is best
The only way to know whether your vitamin D level is normal and how much you should supplement is to test!
My results: then and now
September 2009: I was supplementing with 2000IU vitamin D3 daily. I was not a “sun-worshipper” but I tried to get outside regularly to run and never wore sunscreen unless I was going to be out in the sun for more than an hour. At that time, my vitamin D level was 77 nmol/L, just at the low end of “sufficiency” (76-250 nmol/L)
February 2010: After my test in September, I increased my supplementation to 4000IU vitamin D3 daily over the winter. My vitamin D level increased in that 5 months to 87 nmol/L from the increased supplementation.
November 2014: This time I used a different test that involves doing a finger prick in-office. Once again, my regular supplementation level was 2000IU vitamin D3 daily, and once again I was “mildly” deficient in vitamin D at 70 nmol/L (normal range from this lab is 80-200 nmol/L). So, once again I’m going to increase my supplementation to 4000IU vitamin D3 daily and I should probably continue this dose or slightly lower to keep my levels in the optimal range.