This is part 2 of a 2-part series on vitamin D and why it matters.

We’re approaching cold and flu season. We’re also living with Covid-19 for the foreseeable future. Covid-19 cases tend to spike in colder months.

Does vitamin D play a role in how often you get sick and the severity of your symptoms?

Let’s take a look at the research!

Vitamin D and immune system function

Vitamin D plays a crucial role in immune function and inflammation.

Dating back to at least 1996, peer-reviewed research has shown that calcitriol (vitamin D) plays a role in the immune system.

Wide-ranging actions of calcitriol have further been hypothesized to play a potential role in preventive or therapeutic action in
cancer
chronic conditions such as auto-immune conditions (including type 1 diabetes),
cardiovascular disease, and infections.
The ability of vitamin D to exhibit anti-inflammatory effects on cancer cells by down-regulating the pro-inflammatory pathways, may contribute to cancer inhibition.

source

Vitamin D and Covid-19

Testing positive

Patients with vitamin D deficiency that was not adequately treated were 77% more likely to test positive for COVID-19 than patients who were not likely vitamin D deficient, according to the University of Chicago.

Duration of symptoms

Various studies conducted before the Covid-19 pandemic showed that patients who received vitamin D supplements had a lower risk of acute respiratory infections and a shorter duration of symptoms.

A study found a 59% increased risk of severe COVID-19 infection symptoms among persons with low levels of vitamin D

source

Hospitalization

As of 2023, research across multiple studies shows “a definitive association between the protective role of vitamin D and ICU hospitalization.”

A study found a 45% increase in COVID-19 infection and a 95% increase in resulting hospitalizations.

source, source

Is there an upper limit to vitamin D supplementation?

Yes!

There is such thing as too much vitamin D via supplementation. An excess of vitamin D can become harmful to other processes in the body. This isn’t true of getting vitamin D from sunlight; the body won’t overdo it.

As always, talk to your doctor about what you’re taking.

*Another reason to eat mushrooms. Mushrooms are the only plant food with D. They contain vitamin D2, with lesser amounts of vitamins D3 and D4.*

My experience

Most of us dislike being sick. I’ll do as much as I can to prevent it.

I haven’t gotten Covid. I live in New York City. I take a the subway. I’m on airplanes. I got the first two vaccines. I haven’t had any booster shots. It’s a personal decision. If it’s not broken, don’t fix it may be the best way to describe how I think about this for myself.

I’m focused on caring for my immune system so I don’t have to spend time worrying about Covid.

My goal is to share the research, and my personal experience, so we can live healthier, longer; avoiding the chronic illnesses that science shows are preventable.

Were you aware of the relationship between vitamin D, your immune system, and Covid-19 outcomes? Let me know!

Cover photo by @niaid on Unsplash

Thanks for reading!

Want more content like this?
Subscribe to have the blog post delivered straight to your inbox weekly.

Eat plants. 🥦 Hydrate.🚰 Move.🤸 Prioritize sleep. 🛌

Disclaimer

Please note that some of the links on this website are affiliate links, and at no additional cost to you, I may earn a commission if you decide to make a purchase after clicking through the link. Unless I’ve noted otherwise, all links are to products I use and love.

Your support in purchasing through these links enables me to keep the content free for everyone. Thank you for your support!

Vitamins 201: vitamin D and your immune system