The Emerging Evidence of Vitamin D as a Critical Immune System Booster

Vita-D is no longer just about strong bones

Vitamin D is most commonly associated with sunshine, since our skin can make this fat-soluble vitamin with adequate light exposure. Except we’ve been told since the 1970’s to avoid the sun and block the sun’s rays. And to eat low-fat diets which may interfere with the dietary absorption of Vitamin D from food sources.

Fall sunlight through the trees at Rose Hill Farm (Source: Sue Senger)

Is it any wonder then that as many as 1 in 4 adults have significant Vitamin D deficiency and as many as 1 in 2 have insufficiency (not enough) status. This has become alarming news given the latest research that is changing the way we view and use this important vitamin.

When I was raising my children, the only context for thinking about Vitamin D was around ensuring adequate supplies for the creation of strong bones and teeth. And since I live far enough north that winter sunshine is limited, that meant supplementing my kids through the winter.

I made all of my children’s baby food at home. Baby cereal was just ground rice or oatmeal. Starter foods were simply cooked vegetables, mashed and frozen in ice cube trays for easy portions. Already back then I didn’t trust the additives, sugar and preservatives packed into baby foods. But ensuring they had adequate Vitamin D remained a challenge.

My kids’ grandmother swore by cod liver oil as the way to make sure Vitamin D was in good supply. And so that became my go-to supplement for the kids as the weather turned col and the winter days grew shorter. For the most part it did it’s job. The interesting thing was my kids didn’t get sick as often as others around us, although they had their share of illnesses over the years.

That result is much more understandable in light of new research focused on the role of Vitamin D in the immune system. It turns out to be a far more versatile and essential molecule than previously known.

Updating the science

Vitamin D has now been studied quite extensively for its immune boosting properties, thanks in part to results seen during the Covid-19 pandemic.

But don’t be mistaken - Vitamin D is still essential for healthy bones. In fact, the recent (April 2024) Consensus Statement on Vitamin D Assessment and Supplementation published following the 6th International Conference, “Controversies in Vitamin D,” confirms just that:

Vitamin D deficiency reduces intestinal calcium absorption leading to secondary hyperparathyroidism, bone loss, and increased risk of fractures in older adults.

There are simply more known roles for Vitamin D in the body than previously understood.

These additional roles include (from Reviews in Endocrine and Metabolic Disorders -2022):

• increasing immune system autophagy which is the process by which our bodies respond to infections and clear microbial invaders (i.e., improved anti-bacterial responses);

• increasing protection against a viruses (e.g. hepatitis, HIV, and viral respiratory pathogens including COVID-19);

• directly promoting antiviral immunity against the influenza A (InA) virus;

• providing therapeutic value in relieving the symptoms associated with Covid-19 (e.g. reducing lung and cardiovascular injury);

• and oral doses of D3 have been shown in multiple studies in the UK to reduce Covid-19 symptoms AND mortality risk.

Here’s the bottom line:

Vitamin D deficiency puts you at higher risk of bacterial and viral infections.

The greater the deficiency, the more effective Vitamin D supplementation is at reducing the risk.

Daily oral supplementation over a period of weeks is more effective at raising Vitamin D levels than weekly or booster doses, although loading at the start of an infection may help reduce symptoms.

Humans evolved predominately outside. Today we spend the vast majority of our time inside, away from sunlight. It’s not hard to imagine that the level of D in our systems can drop precariously low.

It’s important to check with your health care provider, and if in doubt get tested, because Vitamin D can interact with certain conditions and medications.

But if you are a healthy individual headed into the cold and flu season, then ensuring your diet is rich in Vitamin D AND taking supplements may reduce your risks of developing illness. Note that the doses in the literature being used to treat or prevent illness are higher than what can be obtained just from eating Vitamin D-rich foods, and much higher than current Vitamin D daily dose recommendations which are still only focused on preventing rickets and bone issues.

It strikes me as sad that there has not been a widespread push to increase Vitamin D daily recommendations and acknowledge the potential role of supplements in reducing seasonal illness based on widespread global research findings.

But then again, no one is going to get rich if people reduced their risk with a cheap and widely available supplement, and that’s the problem with a capitalistic “health” care system that wants to feed it’s bottom line, instead of protecting yours.

I have recently used Vitamin D3 supplements, in conjunction with elderberry and rosehip tinctures, to ward of respiratory illness threatening to park me in bed. I am a believer in the efficacy of boosting my immune system with supplements, and for the most part I am rarely ill despite my exposures.

Let us know in the comments if you use Vitamin D supplements, and what your personal experience has been.

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