Vitamin D is a fat-soluble vitamin that plays a number of critical roles in your body.

This nutrient is especially important for immune system health, leaving many people to wonder whether supplementing with vitamin D may help reduce the risk of contracting the new coronavirus that causes COVID-19.

It’s important to note that there’s currently no cure for COVID-19 and no preventive measures other than physical distancing, also known as social distancing, and proper hygiene practices can protect you from developing this disease.

That said, some research shows that having healthy levels of vitamin D, as well as taking a vitamin D supplement, can help keep your immune system healthy and may protect against respiratory illnesses in general.

This article explains how vitamin D affects immune health and how supplementing with this nutrient may help protect against respiratory conditions.

Vitamin D is necessary for the proper functioning of your immune system, which is your body’s first line of defense against infection and disease.

This vitamin plays a critical role in promoting immune response. It has both anti-inflammatory and immunoregulatory properties and is crucial for the activation of immune system defenses (1).

Vitamin D is known to enhance the function of immune cells, including T-cells and macrophages, that protect your body against pathogens (2).

In fact, the vitamin is so important for immune function that low levels of vitamin D have been associated with an increased susceptibility to infection, disease, and immune-related disorders (3).

For example, low vitamin D levels are associated with an increased risk of respiratory diseases, including tuberculosis, asthma, and chronic obstructive pulmonary disease (COPD), as well as viral and bacterial respiratory infections (4, 5, 6, 7).

What’s more, vitamin D deficiency has been linked to decreased lung function, which may affect your body’s ability to fight respiratory infections (8, 9).

summary

Vitamin D is critical for immune function. A deficiency in this nutrient may compromise immune response and increase your risk of infection and disease.

Currently, there’s no cure or treatment for COVID-19. No studies have investigated the effect of vitamin D supplements or vitamin D deficiency on the risk of contracting the new coronavirus that causes COVID-19.

Still, multiple studies have shown that vitamin D deficiency can harm immune function and increase your risk of developing respiratory illnesses (10).

Additionally, some studies have indicated that vitamin D supplements can enhance immune response and protect against respiratory infections overall.

A recent review that included 11,321 people from 14 countries demonstrated that supplementing with vitamin D decreased the risk of acute respiratory infections (ARI) in both those who were deficient in vitamin D and those with adequate levels.

Overall, the study showed that vitamin D supplements reduced the risk of developing at least one ARI by 12%. The protective effect was strongest in those with low vitamin D levels (11).

Moreover, the review found that vitamin D supplements were most effective at protecting against ARI when taken daily or weekly in small doses and less effective when taken in larger, widely spaced doses (12).

Vitamin D supplements have also been shown to reduce mortality in older adults, who are most at risk for developing respiratory illnesses like COVID-19 (13).

Keep in mind that there’s no scientific evidence that taking supplemental vitamin D can protect you from developing COVID-19. However, being deficient in vitamin D may increase your susceptibility to overall infection and disease by harming immune function.

This is especially worrisome given that many people are deficient in vitamin D, especially older individuals who are most at risk of developing more serious COVID-19-related complications (14).

For these reasons, it’s a good idea to have your healthcare provider test your vitamin D levels to determine whether you have a deficiency in this important nutrient.

Depending on your blood levels, supplementing with 1,000–4,000 IU of vitamin D per day is typically sufficient for most people. However, those with low blood levels will often require much higher doses to increase their levels to an optimal range (15).

Though recommendations on what constitutes an optimal vitamin D level vary, most experts agree that optimal vitamin D levels lie between 30–60 ng/mL (75–150 nmol/L) (16, 17).

summary

Evidence that vitamin D supplements reduce the risk of developing COVID-19 is lacking, but having healthy vitamin D levels can enhance immune health. Plus, vitamin D supplements may protect against respiratory infections in general.

Vitamin D plays many important roles in your body, including promoting the health of your immune system.

Scientific research suggests that supplementing with vitamin D may protect against respiratory infections, especially among those who are deficient in the vitamin.

Still, keep in mind that there’s currently no evidence that taking any supplement, including vitamin D, reduces your risk of developing COVID-19 as a result of contracting the SARS-CoV-2 coronavirus.

If you’re interested in supplementing with vitamin D to enhance your overall immune response, consult your healthcare provider for information on proper dosing.