Vitamin D is a fat-soluble vitamin present in vitamin-rich foods and produced in the skin in response to being exposed to UV rays – aka sunlight. Recent research has shown that taking vitamin D supplements reduces the risk of developing certain respiratory infections, like the influenza virus. Now, and in light of the COVID-19 pandemic, investigators think that vitamin D could also reduce the risk of contracting the coronavirus.

Vitamin D and immunity

Vitamin D plays many vital roles in the body, including aiding in calcium and phosphorus absorption, two essential compounds for healthy bones and teeth. Several studies have found links between vitamin D deficiencies and mood disorders, particularly depression. Laboratory studies have also found that vitamin D can reduce cell cancer growth and lower the risk of developing infections.

Supplementing with vitamin D may protect against acute respiratory tract infections, according to a 2015 systematic review and analysis of past studies. Published by the British Medical Journal, the reviewers looked at 25 clinical trials with over 11,000 participants in total to see if vitamin D supplements could potentially prevent respiratory infections.

The results showed that vitamin D supplementation reduced the risk of contracting at least one respiratory infection. Additionally, vitamin D was particularly effective at preventing respiratory infections among those who already had a deficiency.

Other reviews of the existing literature have found similar results, like this 2018 meta-analysis, which concluded that vitamin D supplements may have a protective effect against the influenza virus. However, some of the studies that they analyzed had no relevant results.

But despite being so crucial for health, vitamin D deficiency remains a public health issue. About 1 billion people have vitamin D deficiency worldwide, and nearly 50 percent of the entire world’s population has vitamin D insufficiency. In the United States, it is estimated that almost 40 percent of Americans are vitamin D deficient. Vitamin D deficiency is common among dark-skinned individuals, older adults, people who are obese and overweight, and hospitalized patients.

Vitamin D and COVID-19

Vitamin D had been previously shown to protect against respiratory viruses like influenza, and recent analyses demonstrate that the same could be true for COVID-19.

One study led by Northwestern University researchers compared COVID-19 data from 10 countries to each country’s average vitamin D deficiency rates. They found that countries with more vitamin D deficiency had higher mortality rates, whereas countries with higher vitamin D levels were not affected as severely by the virus.

Several observational studies conducted at South Asian hospitals show that the prevalence of vitamin D deficiency was significantly higher among patients with severe coronavirus cases. An analysis of 489 patients records from the University of Chicago found that people who had vitamin D deficiencies before the pandemic were substantially more likely to receive a positive COVID-19 diagnosis than people with normal levels.

Further, according to a population-based study conducted in Israel, low plasma vitamin D levels increased the likelihood of COVID-19 infection even after adjusting for age and other demographic factors. Finally, a recently published Boston University study revealed that those who are vitamin D deficient have a 54 percent higher risk of getting infected with COVID-19.

How much vitamin D should I take?

According to the National Institutes of Health (NIH), the recommended daily amount of vitamin D is 400 international units (IU) for babies up to 12 months, 600 IU for healthy individuals 1 to 70, and 800 IU for those older than 70 years. However, these daily intakes vary depending on several factors, including how much sun a person is exposed to, their diet, and whether they have a preexisting medical condition.

Now may be a good time to get your vitamin D levels checked if you haven’t done so already. The normal range of vitamin D is measured in nanograms per milliliter (ng/ml), and experts recommend aspiring for a vitamin D concentration of no less than 40 ng/ml.

Vitamin D deficiency is very common and may not always produce any signs or symptoms, but the good news is that it’s easy to fix. Increasing your sun exposure; eating more vitamin D-rich foods like salmon, egg yolks, mushrooms, or fortified foods; and taking a supplement are all effective ways of boosting your vitamin D intake.

Curt Hendrix, MS, CCN, CNS

Curt Hendrix, MS, CCN, CNS
Akeso Health Sciences Co-founder and Chief Scientific Officer, Curt Hendrix, MS, CCN, CNS, has an unwavering commitment to help people with chronic health issues. Curt holds advanced degrees in chemistry and clinical nutrition and has dedicated his life to the research and development of innovative natural medicines.