For years, it’s been known that being deficient in vitamin D increases the risk of developing certain respiratory infections. Early in the COVID-19 pandemic, there was speculation that making sure your vitamin D level is adequate might be a way to help reduce the risk of getting the viral infection — but there wasn’t any hard evidence to support this idea at first.
Now, a study shows that being deficient in vitamin D is, in fact, associated with a higher risk of developing COVID-19 — even after adjusting for other factors that might affect a person’s infection risk. What’s more, people with diabetes were found to be at an increased risk for both vitamin D deficiency and COVID-19.
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Large differences in COVID-19 risk
The study, published in the journal Nutrition, had a couple of main goals. One was to find out if vitamin D deficiency directly increases a person’s risk of developing COVID-19. Another goal was to find out if the higher COVID-19 risk seen in certain groups — including people with diabetes and Black Americans — might be explained, in part, by a higher rate of vitamin D deficiency.
Vitamin D is critical to the functioning of your immune system, so any deficiency can make it harder for your body to fight off viruses and other pathogens (like bacteria and fungi) that can cause infections. While it can be found in a few foods, the most common natural source of vitamin D is sunlight exposure on your skin — which causes your body to create its own vitamin D. Many people don’t get enough sun exposure to have adequate vitamin D levels, especially during winter months. If your vitamin D levels are found to be insufficient, your doctor will probably recommend taking a vitamin D supplement.
For the current study, researchers looked at patient records at the University of Florida Health Center between October 2015 and June 2020 to look for a diagnosis of vitamin D deficiency. They then looked at COVID-19 diagnosis records to see if there was a link between the two conditions. Overall, patients with a diagnosis of vitamin D deficiency were found to be 4.6 times as likely to get COVID-19 as people with no diagnosis of a vitamin D deficiency.
The researchers then looked at several factors that were tied to a person’s risk of vitamin D deficiency, to see if the link to COVID-19 was still present once these factors were adjusted for. They found that after adjusting for participants’ race, vitamin D deficiency was still independently associated with 3.8 times the risk of developing COVID-19. After adjusting for diabetes status, vitamin D deficiency was tied to 3.3 times the risk of developing COVID-19, and after adjusting for obesity, vitamin D deficiency was tied to 2.3 times the COVID-19 risk. After adjusting for patients’ age, vitamin D deficiency was tied to a whopping 5.2 times the risk of developing COVID-19
The differences in COVID-19 risk after making these adjustments also demonstrate the higher rates of vitamin D deficiency seen in certain groups. There wasn’t much difference in vitamin D deficiency between men and women, with women 1.1 times as likely to be deficient. But Black people in the study were 3.4 times as likely to be deficient as people of other races, and people with diabetes were 2.9 times as likely to be deficient as those without diabetes. People with obesity were 4.9 times as likely to have vitamin D deficiency as others in the study.
Making sense of the link between vitamin D and COVID-19
This study strongly suggests that vitamin D deficiency is an independent risk factor for COVID-19, since there was a link between the two diagnoses even after adjusting for several different factors, like race, diabetes status, obesity status and age. But at the same time, it suggests that certain groups — including Black people, people with diabetes and obese people — may need to be extra vigilant about screening for and treating any vitamin D deficiency, due to a higher likelihood of being vitamin D deficient.
No matter your race or health status, it’s a good idea to get your blood level of vitamin D tested at your doctor’s office, if you haven’t done this in the last few years. Making sure you aren’t deficient — and taking any vitamin D supplements as needed — could help limit your risk of of getting COVID-19.
Want to learn more about coronavirus and diabetes? Read our latest COVID-19 updates.