What exactly is Vitamin D? And why are low levels of it really bad for you?

Vitamin D, unlike the other vitamins and minerals, is actually a steroid hormone since its structure and behaviour is more akin to that branch of molecules than it is to vitamins. (Vitamin D, steroid hormones, and autoimmunity – PubMed). It’s also fat-soluble, so unlike other vitamins, it should be consumed with fat to ensure it’s being absorbed properly.

As a steroid hormone, it promotes:

• Bone health (by regulating calcium and phosphorus to promote growth)
• Boosts immune function
• Enhances muscle function
• Supports heart health

In addition to these and other benefits, it also plays an important role in mental health by regulating serotonin and dopamine. Low Vitamin D levels are also associated with symptoms of depression and anxiety, which would definitely explain seasonal affective disorder (SAD). Is Vitamin D Important in Anxiety or Depression? What Is the Truth? – PMC

You produce Vitamin D3 through sun exposure and can also get it from food sources such as fatty fish, egg yolks, and various other fortified foods such as milk and plant-based milk.

Why it became a concern for me

On a random visit to my doctor to check on some things, I discovered that I had actually pretty low levels of Vitamin D, which explained why my body was having trouble fighting infections and also why I always felt so depressed during winter. Since I have darker skin, she had suggested I aim to supplement a lot more Vitamin D than I was doing (which was maybe 400IUs every other day).

I’ve now increased the dosage to about 4000IUs every day using sublingual (under the tongue) drops and that has made a pretty big difference in both my immune system (fighting off colds faster and catching them less frequently) and has also been a huge boost to my mood during the horribly depressing winters of Canada. In fact, to sufficiently provide the many benefits that it does, that should be the target for most adult individuals according to this study Vitamin D: Evidence-Based Health Benefits and Recommendations for Population Guidelines – PMC.

Why could it be a concern for you

Most people who live in the northern hemisphere are deficient in this vitamin. Canadians especially won’t get enough Vitamin D from just diets during the winter since there’s barely any sun exposure. It’s even more concerning if you have darker skin since we’re used to having a much higher sun exposure and have the melanin to absorb it.

Vitamin D toxicity is rare and would come from over-supplementing, but that would mean taking something like 10,000IUs or more for an extended period of time. The negative effects of having too much Vitamin D also don’t seem to be nearly as bad as the negative effects of having too little.

But this is why I’d recommend checking in with your doctor just to see where your levels are and if you need to supplement, or supplement more, to make sure it’s at a good place. It could be an answer to some of the issues you’re facing in winter.