Should You Take Extra Vitamin D Before Your Next COVID Shot?

A vitamin D deficiency may affect how well your immune system responds to the COVID-19 vaccine, according to newly-published research out of Italy.

Milan-based researchers found that adults with a vitamin D deficiency had lower antibody levels nine months after receiving their second dose of the COVID-19 vaccine compared to adults with normal vitamin D levels.

The study, published in the medical journal Endocrine, looked at 119 healthcare workers—median age 53 years old—who received two doses of the Pfizer-BioNTech vaccine. The findings suggest that people who are vitamin D deficient might want to get their levels up prior to getting the COVID shot.

“Interestingly, our data was obtained in relatively young subjects with a limited prevalence of hypovitaminosis D (vitamin D deficiency),” Andrea Giustina, MD, a professor of endocrinology and metabolism at San Raffaele Vita-Salute University and co-author of the research, told Verywell. "It may be hypothesized that the impact of our data may be even greater in older populations with a much higher prevalence—and severity—of vitamin D deficiency."

According to Purvi Parikh, MD, an allergist and immunologist at NYU Langone Health, people with vitamin D deficiency should aim to get their levels up to improve immune response, but taking "megadoses" of supplements immediately before a shot likely won't do the trick. Instead, people need to make vitamin D part of their everyday lifestyle to improve levels in the long-term, she said.

But what about people without a vitamin D deficiency—is it worth taking supplements ahead of a COVID booster? According to Parikh, no. 

“There’s no evidence that this will improve immunity to a booster if levels are already normal,” Parikh told Verywell. “There’s always a risk of over supplementing, so do not get over zealous and follow your doctor's orders.”

Consistency Matters With Vitamin D

Vitamin D plays many roles, including helping the body absorb calcium and helping the immune system ward off diseases and viruses. 

A lack of vitamin D can impact your health. Research shows that vitamin D deficiency can put people at an increased risk of infections—including respiratory infections.  

During the height of the pandemic, some research suggested that vitamin D could reduce the likelihood of developing severe illness from COVID—though opinions on this are mixed.

But Parikh said that having a healthy vitamin D baseline is good for many health outcomes—not just COVID severity. 

“This is one aspect of a health-optimization strategy and should be in conjunction with having a healthy weight, staying active, and getting enough sleep and hydration,” Parikh said. “Taking megadoses of vitamin D while acutely ill with COVID likely won’t do much, but [vitamin D] should be employed as a preventative strategy in advance of getting ill.”

In the case of the antibody response from the vaccine, Giustina said his research wasn’t designed to study why vitamin D deficiency was tied to lower antibody levels. His working hypothesis, however, is that if someone is vitamin D deficient, their immune response may not be as robust as someone with normal levels. 

More research is needed, he said, to further understand the decline in antibody levels in vitamin D deficient people compared to non-deficient ones. 

How Do You Get Vitamin D?

You can get vitamin D from the sun, as the body makes the nutrient when exposed to sunlight. You can also get it from vitamin D-rich food, like fatty fish such as salmon, tuna, and trout. Food that is fortified is also a good source, including milk and milk alternatives, like soy or almond milk. 

Not everyone gets enough vitamin D—especially people who live in parts of the world where there’s less daily sunlight. Vitamin D deficiency can cause health problems like brittle bones and muscle weakness, and symptoms can include muscle and/or bone pain, “pins-and-needles” in the hands or feet, and muscle weakness near the trunk of the body, like upper arms or thighs.

“Sun exposure is responsible for 80% of endogenous vitamin D production, and in the winter, levels of vitamin D reach their nadir [lowest point],” Giustina said. “Therefore, it could be hypothesized that vaccinating people before the winter could be more effective in maintaining a more sustained response to the vaccine.”

People with a vitamin D deficiency might not always know it, as symptoms such as muscle pain can be attributed to any number of causes. But a blood test can determine whether or not your levels are high enough. 

For people who need to increase their vitamin D levels, supplements are a popular choice. Consult your healthcare provider about how much you need, since factors such as age, weight, and health history can all affect dosage.

There is, however, such a thing as too much vitamin D. The NIH warns that excessive vitamin D consumption—which is most often caused by taking too many vitamin D supplements—can lead to nausea, vomiting, muscle weakness, pain, loss of appetite and dehydration. On the extreme end, it can cause kidney failure, irregular heartbeat and death.

That's why understanding your levels and nutritional needs is important.

"Vitamin D isn’t a magic bullet that will work overnight," Parikh said. "It takes time to build levels up, so supplementation should start as soon as you know you are low—and under guidance of your doctor."

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.