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Long COVID treatment: Does your vitamin D level play a role?

BY Kenny Cheng April 29, 2024

We’ve long known that soaking up more sunlight can boost serotonin levels and improve mental health by ramping up vitamin D production. Now, a group of researchers who analyzed dozens of studies, dating from January 2022 to August 2023, have found that having low levels of vitamin D may increase risk of severe COVID-19—and may raise risk for and possibly delay recovery from Long COVID. The research team also identified a possible interplay between vitamin D and metformin, a medication that may help prevent Long COVID.

The clinical review, conducted by researchers at Assiut University in Egypt and published in Inflammopharmacology, analyzed 58 clinical studies that investigated the therapeutic effects of vitamin D in more than 14 million patients with COVID-19. The authors found that 49 studies (86%) demonstrated that having a higher vitamin D level was associated with less severe COVID-19 symptoms. The researchers concluded that vitamin D likely acts against COVID-19 by protecting the respiratory system and regulating the innate and adaptive immune system.

It looks possible that vitamin D also plays a role in Long COVID. In the review, the researchers stated: “There are promising reasons to enhance research on the effects of vitamin D supplements in Long COVID patients.” They found four observational studies that supported the role of vitamin D deficiency (hypovitaminosis D) as a possible risk factor for Long COVID. This builds upon previous evidence that found Long COVID patients had lower vitamin D levels compared to their counterparts without Long COVID, underlining the potential for vitamin D to help prevent the condition.

The finding also provides an opening for the use of metformin, a drug investigated in a recent Long COVID phase 3 clinical trial. In this trial, early treatment of COVID-19 with metformin, a drug used since the 1950s to treat type 2 diabetes, reduced the need for health care services for severe COVID-19 by 42.3% after 14 days and the risk of Long COVID by 41.3% during a 10-month follow-up.

In their conclusion, the authors explain that their study suggests a new potential treatment for both COVID-19 and Long COVID: vitamin D supplementation combined with early use of metformin, which has been observed to target “multiple pathological pathways of COVID-19 in a diabetes-independent manner.” The researchers argued that randomized controlled trials using a vitamin D/metformin cocktail could provide an important and much-needed new approach to the treatment of Long COVID.

Kenny Cheng is an undergraduate majoring in molecular, cellular, and developmental biology at Yale University.

The last word from Lisa Sanders, MD:

This study was a survey of investigations into the role that vitamin D plays in the severity of COVID-19 and the risk of Long COVID. Many studies have shown that low vitamin D levels put individuals at risk of having more severe infections with the SARS-CoV-2 virus. Some suggest that treatment with vitamin D may speed recovery and reduce the risk of developing Long COVID.

This is bolstered by research into the use of metformin during acute COVID infections to reduce the likelihood of developing Long COVID. The physiology of this protection is thought to be due to metformin’s effect on the vitamin D receptor, suggesting that increased vitamin D levels may reduce the risk of developing Long COVID. Randomized controlled trials will tell us if it really helps once you have Long COVID.

Much of the world’s population, especially northern Europeans, Americans, and residents of the Middle East, are deficient in vitamin D. And studies of vitamin D in the treatment of COVID-19 show that those with deficiencies are most likely to benefit from vitamin D supplementation. So, should we all be taking vitamin D—just in case we get COVID? Maybe.

There are lots of benefits from having the right amount of vitamin D. It’s good for your bones and muscles. It has many other important benefits, and there’s good research that having enough is important for overall health. Luckily, there is a free source of vitamin D—the sun. Most people can get all the vitamin D they need with five to 30 minutes of sunshine, most days a week. If you are concerned about skin aging, as I am, then put sunscreen on your face but leave your arms and legs exposed while you get your regular dose. After your sun bath, you can apply sunscreen everywhere else. As with everything in life, too much of a good thing can be bad. Taking 1,000 IU of vitamin D3 daily is sufficient for most adults who don’t get the sunshine.

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