Vitamin D, which is actually a pro-hormone and not a vitamin at all, regulates the function of over 900 genes. Besides being important for bone, cardiovascular, mental emotional health, and optimizing blood sugar levels, vitamin D is essential for optimal immune function. It has more recently been discovered that cells of the immune system possess vitamin D receptors and make enzymes capable of converting vitamin D into its active form.
Cold and flu season is here and those with higher vitamin D levels contract substantially fewer infections.
How does vitamin D help boost immunity? The answer lies in two of its mechanisms.
1. Downregulation of pro-inflammatory cytokines:
When compared to anti-inflammatory cytokines which promote healing and reduce inflammation, pro-inflammatory cytokines do the opposite. These cytokines are largely responsible for the unpleasant symptoms you get during the flu. Our recovery depends on a balance between these two types of cytokines.
2. Upregulation of antimicrobial peptides:
The primary antimicrobial peptide that is stimulated when optimal vitamin D status is achieved is cathelicidin which is produced by immune cells and cells that line the skin, respiratory tract, and gastrointestinal tract. It has a broad spectrum antimicrobial effect against gram positive and gram negative bacteria, viruses, and fungi.
Why is vitamin D deficiency so common?
Two thirds of Canadians don't get enough vitamin D, especially from October through April. Only one third of those who do have levels that are considered optimal. Common reasons include living in a higher latitude (hello Alberta!), less sun exposure (hello Alberta winters!), low dietary intake (most notably in vegans), gastrointestinal malabsorption issues, and vitamin D depleting medications (I'm lookin' at you, cholesterol lowering drugs). Foods rich in vitamin D include fatty fish, cheese, egg yolks, and beef liver. That being said, vitamin D is primarily produced in response to sun exposure rather than being absorbed from the diet.
What can we do about it?
If you're in Alberta, you may know that as of 2015, Alberta Health Services is no longer funding vitamin D testing for the general population as it is now deemed an unnecessary expense. I routinely test vitamin D status for my patients. Doing so allows for a more targeted approach to vitamin D supplementation and ensures that optimal levels will be reached. Book an appointment today to get your levels checked and avoid getting sick this winter!