Does Vitamin D Prevent Colds? The Latest Research

Vitamin D is good for your bones.  Not getting enough vitamin D has been linked to heart disease, cancer, and dementia.  But does vitamin D prevent colds?  In this article, I review the latest research looking at vitamin D, colds, the flu, and other respiratory tract infections.  If you, or a loved one, has been sick this year, you won't want to miss this article.

My Vitamin D Challenges

As readers know, I'm not a fan of supplements unless it is for a critical nutrient or vitamin that you can't get naturally.  For me, vitamin D fits this category.

I recently had my vitamin D level checked at the end of the summer.  I picked this time because I wanted to see what my levels were in the best possible situation.  As I often go on long mountain bike rides or trail runs during the summer, I figured my vitamin D levels would at least be normal this time of the year.

I was wrong.  Even with eating fish and a lot of sun exposure, my vitamin D level came back at 25 ng/mL.  At my hospital, the normal range for vitamin D is 30 to 80 ng/mL.

Knowing that I have a clear vitamin D deficiency that can't be corrected naturally, I have faithfully taken a vitamin D supplement this winter.  Remarkably, even with four young children, frequent periods of sleep deprivation while being on call at the hospital, and several colds that went through our family, I have not been sick once this year.

I figured it was my healthy diet protected me against colds, the flu, and other respiratory tract infections.  But then, this study  just came out.  Based on my careful review of this study, perhaps it is my daily vitamin D supplement that is protecting me from getting sick this winter.

The Vitamin D and Colds Study

This past week in the prestigious British Medical Journal, 25 researchers from Harvard University, and other major medical centers from around, the world published their findings on vitamin D supplements and the risk of respiratory tract infections.  In this study, researchers pooled the results of 25 vitamin D studies involving 11,321 people.  Here are their four main findings:

1. Taking any vitamin D supplement reduced your risk of getting an upper respiratory tract infection by 12%.

2. Those taking a daily dose of vitamin D were 19% less likely to get an upper respiratory tract infection.

3. For people with a documented vitamin D deficiency, a daily dose of vitamin D reduced their chances of getting an upper respiratory tract infection by 70%.

4. There were no statistically significant complications of taking vitamin D observed in this study.

What does this study tell us?

The key message of this study is that a daily dose of vitamin D seems to be protective against colds and other illnesses.  However, for those with a documented vitamin D deficiency, like me, the protective effects are literally off the charts.

When the researchers looked at dosing frequency, a daily dose of vitamin D appeared to be most  protective.  This is probably because periodic big doses of vitamin D changed gene expression and other metabolic pathways.

What doesn't this study tell us?

First, it doesn't tell you how much vitamin D you should take.  As this study pooled the results of 25 previously published studies, the vitamin D dose used in every study was completely different.  Thus, as everyone's need for vitamin D varies, please ask your doctor what dose is right for you.  Please note that you may not even need a supplement at all.

Second, this study didn't find that you had to get your vitamin D above a certain level to be protected from colds or other illnesses.  Rather, just taking a daily dose of vitamin D seemed to be what was important.

How does vitamin D protect you from colds?