2 Ways Optimal Vitamin D Levels Help Fight Acute Respiratory Infection

The acute respiratory infection is the most common infection in humans. Research shows supplementation with vitamin D may help protect you.

When it comes to viral infections, like a common acute respiratory infection, as much as we may like to believe it, we can’t hide from them. In fact, you’ve got more viruses in and on your body now than bacteria. Thankfully, we have what seems to be a comfortable, friendly relationship with the vast majority of them. However, there are those that are a bit more nefarious (I’m looking at you SARS-CoV-2). To combat those, we look to antiviral drugs or lifestyle interventions, like optimal vitamin D levels.

With well over 500 million respiratory tract infections in the US each year, they are the most common illness in humans. They cause more absences from school or work than any other illness, and they’re expensive too, costing us $40 billion annually. The cost is even higher worldwide where acute respiratory infections are responsible for over 6% of deaths and disability.

Unfortunately, when it comes to antiviral drugs, our catalog of helpful options is limited. Unlike antibiotics, which go after the bacteria and not your cells, antivirals can wreak a bit more havoc. The challenge in developing antivirals is that they “can damage host cells where the viruses reside.”

Regardless, antivirals obviously play an essential role in helping us overcome viruses, especially novel or particularly nasty ones. We need to remember, though, that our bodies are designed to, at the very least, put up an effective fight on their own. To do so, however, they need to have the tools to perform optimally. Fast food, a sedentary lifestyle, non-stop stress, sitting at a desk for 12 hours a day, and a couple of hours of sleep each night isn’t going to cut it.

Optimal vitamin D levels may help prevent acute respiratory tract infection

Though bacteria can cause some respiratory tract infections, the vast majority are caused by viruses. While most of these infections are mild, they still result in 20 million missed days of school and more than 20 million lost days of work every year. Complications tend to be rare, but some infections—like the flu or COVID—can result in much more problematic issues like pneumonia.

A 2017 study in The BMJ found that vitamin D supplementation helped protect against acute respiratory tract infection. Two important points to come out of this extensive review:

  1. Folks with lower baseline vitamin D levels (less than 30 ng/mL) saw bigger benefits from supplementing than folks who already have higher vitamin D levels (over 30 ng/mL). Researchers actually concluded that there was no additional “protection” once vitamin D levels were higher than 30 ng/mL.
  2. Vitamin D supplementation appears to offer protection against respiratory tract infections when taken regularly in smaller doses, rather than a short burst of larger doses (much like vitamin C).

A 2012 meta-analysis looked at five clinical trials. These trials administered doses of between 400 IU/day and 2,000 IU/day, with one study only doing a single dose of 100,000 IU. Overall, there were 10% fewer respiratory tract infections in those taking vitamin D than in the placebo groups.

A more recent study seems to confirm the lack of preventative benefit from large doses of vitamin D. In this study, researchers concluded that large, single doses of 60,000 IU of vitamin D, administered once a month, “did not reduce the overall risk of acute respiratory tract infection…” Given the results of the large 2017 study referenced above, this isn’t surprising. Smaller, daily doses may have shown to be more effective.

A study published in January 2022 in the American Journal of Clinical Nutrition also backs the idea that large doses aren’t as effective. In this study, researchers found no improvement on cytokines, chemokines, and growth factor from a single dose of 200,000 IU of vitamin D in hospitalized patients with moderate to severe COVID-19.

A 2013 review also found that vitamin D has protective properties against respiratory tract infections, with daily doses being the most effective.

Optimal vitamin D levels chill out your immune system

Vitamin D plays a role in regulating the responsiveness of your innate immune system. Specifically, it helps regulate receptors that detect viral infections. This “first line of defense” rings the alarm so your body can get a handle on it quickly. When this defense mounts, however, it can get out of hand. This overeagerness by the immune system is often referred to as a “cytokine storm.” This overproduction of too many inflammatory cytokines leads to the production of too many other immune cells. Ultimately, this hyperactivation causes systemic inflammation that can be life-threatening.

So, when it comes to viruses, having an immune system that’s a bit more laid back can be a good thing. Research suggests that major complications from viral infections such as the flu and COVID may be from the cytokine storm, not the virus itself. If that’s the case, keeping your immune system from getting too excited may be helpful in avoiding poor outcomes. Maintaining optimal vitamin D levels can help keep your immune system chill while still allowing it to efficiently tackle viral invaders.

A word about COVID-19 and vitamin D

When talking about viruses today, it’s impossible not to include at least a mention of SARS-CoV-2, the virus that causes COVID-19. When it comes to COVID outcomes and vitamin D, there are several studies that indicate vitamin D may be helpful.

This 2021 study from the Journal of Medical Virology found that “vitamin D deficiency was found to be associated with a higher COVID‐19 risk.”

Researchers from this 2021 study from the journal BMC Infectious Diseases found that a high number of their hospitalized COVID-19 patients had vitamin D deficiency. They concluded that “…low 25OHD levels at hospital admission were associated with increased IL-6 levels and predicted both the severity of respiratory distress and mortality during the course of hospitalization, independently of other comorbidities.”

A 2021 study in the Journal of Endocrinological Investigation found that “the rate of SARS-CoV2 infection was significantly lower in vitamin D-sufficient patients supplemented with cholecalciferol…than in patients vitamin D deficient not receiving vitamin D supplements. Similarly, vitamin D-sufficient patients on cholecalciferol supplementation had a lower risk of severe COVID-19…and lower COVID-19 mortality…compared to vitamin D-deficient unsupplemented patients.”

When it comes to guarding against viral infections, vitamin D can be a helpful tool to have in your toolbox. Like most tools, however, it needs to be used properly to be effective. Taking smaller, daily doses to keep levels up and consistent can be more effective than taking larger doses once you get sick.

Consistently taking vitamin D supplements can help maintain optimal levels—especially for those of us north of 37 degrees latitude (think Santa Cruz, CA). Regularly testing your levels is quick and easy. I use this one from Ulta Lab Tests. It’s only $39, no health insurance is needed, and I get results sent directly to me quickly—sometimes the same day.

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