Vitamin D and Immunity: Is My Supplement Why I Get Sick Less Often?
Last updated: April 2023
I used to catch a cold at the drop of a hat. If someone near me sneezed, chances were that I'd show symptoms within a day.
But I haven't had a viral or bacterial infection for almost two years. I’ve never tested positive for COVID-19.
I'm not saying this to brag; I'm genuinely confused as to how I've gone this long without a sore throat, cough, or stuffy nose. Pandemic isolation aside, I typically get sick no less than 2 or 3 times a year.
It's worth noting that I practice all the good hygiene habits of 2020, including washing my hands for two full rounds of the "Happy Birthday" song.
I also exercise regularly, try not to touch my face a lot, work from home, and stay up-to-date on recommended vaccines. The surgery I had in 2021 to open my collapsed and swollen nasal passages also helped me breathe easier.
But to everyone who knows me, it’s remarkable that I’ve been in close contact with multiple sick people, my husband included, without falling ill.
I’m sure there's a cold or coronavirus infection in my future. But this wellness spell inspired me to dig a little deeper into my immune health.
Vitamin D and immunity
This fat-soluble vitamin is key for brain and bone health. It also helps us absorb calcium and keeps our muscles and nerves working the right way. But it's also a big part of how the immune system fights off viruses and bacteria. Not until a few years ago did my levels climb above normal.
How did I get my vitamin D levels up?
This is a good question, and I'm not sure there’s a single answer. I say that because, historically, I’ve really struggled to get my vitamin D levels above 30 ng/ml. That’s the lowest threshold for what my doctor and the National Institutes of Health (NIH) consider optional.1
But my lab tests started to improve in 2019. While I still have a chronically low white blood cell count, my vitamin D levels have risen steadily from 28 to 43.
Here are a few things that happened during the past few years:
- I went gluten-free. Research on people with celiac shows that a long-term gluten-free diet can help boost vitamin D levels in people who can’t tolerate wheat. In the fall of 2019, my GI doctor diagnosed me with non-celiac gluten sensitivity and suggested I give up wheat to improve my malabsorption issues.2
- My GP fine-tuned my vitamin D dose. For more than three years, I’ve taken a daily vitamin D3 supplement of 5,000 IU. That’s more than what’s recommended for the general population, which is why my doctor checks my levels ever year.
- Vitamin D is part of my daily routine. I used to forget to take my supplement, but now I put it next to my coffee to remind me.
- Sunshine is part of my prescription. My doctor suggested I add a daily sunshine supplement in the spring and summer. (I live in the Midwest.) When possible, I’ll sit outside without sunscreen on for at least 10 minutes.
Talking to your doctor about supplements
According to the NIH, the recommended amount of vitamin D for adults is between 600 IU to 800 IU per day. But that wasn't enough for me. And what you’ll need depends on a number of factors, including your age, current vitamin D levels, and other health conditions.1
I wasn't technically deficient, but my vitamin D levels were below normal when my doctor first checked them. To fix things quickly, she had me try a megadose of 50,000 IU a week.
This was before my gluten-free days, and my numbers barely budged after 3 months. She blamed malabsorption.
After some trial and error, we saw some improvement after I started 5,000 IU per day. And maybe going gluten-free plays a part in my ability to absorb the vitamin now.
If I’m ever able to get my levels in the 50s — what the NIH says is “adequate” for bone and overall health — I may be able to lower my dose.1
Keep in mind it’s possible to store too much vitamin D. That’s why it’s generally not recommended that you start a supplement without talking to your doctor first.
But you can get a simple blood test to check your levels to gauge what dose is right for you.
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