Vitamin D is a pro-hormone with ubiquitous effects throughout the body. It has been shown to have a multitude of benefits, including bone health, innate and adaptive immune function, and vascular health, yet we live in country where, depending on the source you consider, 40-70% of the population is vitamin D deficient and people are routinely told to limit sun exposure.

However, there is a growing body of data now showing vitamin D deficiency (serum 25-OH-D < 20 NG/mL) as a risk factor for severe cases of COVID-19, as well as highlighting the benefit of vitamin D supplementation in overcoming COVID-19. Dr. Michael Holick, a well-known vitamin D researcher at Boston University, demonstrated a 54% decreased risk of getting COVID-19, as well as a decreased risk of complications, in patients with sufficient vitamin D levels. He also observed lower vitamin D levels in patients living in predominantly African-American and Hispanic zip codes.

In a recent op-ed article, Richard Carmona, MD, a former Surgeon General of the United States, called for identifying and eradicating vitamin D deficiency with early and aggressive supplementation. As COVID-19 cases continue to surge in the US, and as the vaccine rollout is less than optimal, we as practitioners struggle to help our patients remain healthy, while simultaneously trying to remain disease-free ourselves. It appears that we should look at the work of our European colleagues for some sage advice on vitamin D. Multiple studies are emerging showing its benefits.

Does vitamin D deficiency lead to worse COVID 19 outcomes? The answer is yes. A large meta-analysis by Pereira et al showed patients with low vitamin D had aggravated course of COVID-19. In one study, Jain et al showed that in deficient patients, the fatality rate was 21%, while in those with higher levels it was < 3%. Interestingly, 97% of severely ill ICU patients had vitamin D deficiency, but only in 33% of asymptomatic patients. 

If vitamin D deficiency predisposes patients to COVID-19, the next question to ask is whether vitamin D supplementation benefits patients with COVID-19? Again, the answer is yes. In a study on 40 patients with COVID-19 and vitamin D deficiency, supplementation with vitamin D showed faster clearance of the virus. In a Spanish study on 76 hospitalized COVID-19 patients who received a potent, fast-acting vitamin D analog, only 2% needed ICU admission, compared to 50% of the untreated group.

In France, researchers looked at records of nursing home residents, some of whom receive a bolus of 20-50,000 IU vitamin D per month. Only 10% of supplemented patients progressed to severe COVID-19 compared to 31% of the non-supplemented group. Fourteen-day mortality rates were 7% in the supplemented group versus 31% in the non-supplemented group.

So, when should you give vitamin D? Studies show that giving vitamin D3 ten days after COVID-19 starts is not helpful. This is understandable, given that it may take a week or so for the body to convert vitamin D3 to its active form. As functional medicine practitioners, it behooves us to supplement our patients early with a target of 40-60 NG/mL. Remember that vitamin D may theoretically interfere with some drugs and vice versa, so use it wisely!


Steve Amoils, MD

Steve Amoils is the Co-Medical Director of the Alliance Integrative Medicine (AIM) in Cincinnati, together with his wife Sandi Amoils, MD. He is an Adjunct Assistant Professor in the Department of Medical Education at the University of Cincinnati and President of the Ohio Chapter of the American Academy of Medical Acupuncture, and has been practicing Functional Medicine since 2000. He has received numerous awards for his achievements, including America’s Top Doctor in Family Medicine and Cincy Top Doctor yearly since 2007.

Trained in South Africa, London, and then in the United States, Steve is a board-certified family physician. After completing medical training in South Africa in 1984, he and Sandi spent two years traveling around the world, studying various indigenous medical systems. In 1987 they immigrated to the US, where they ultimately both practiced as family physicians in Cincinnati. In 1999, at the behest of a large hospital group, they opened Alliance Integrative Medicine to offer patients a comprehensive, personalized, integrative approach to medicine. AIM has been recognized nationally as a leading center in integrative medicine since 2004, and Dr. Amoils has been a site investigator on three major national studies on integrative medicine. AIM averages approximately 30,000 patient visits per year. Alliance Integrative Medicine offers an accredited physician fellowship training program in integrative medicine.

Through the nonprofit Integrative Medicine Foundation, the Amoils are active in research, education and overseeing the Get Well program for the underserved. Steve and Sandi are co-authors of Get Well & Stay Well – Optimal Health through Transformational Medicine. The book expounds on their philosophy of helping patients transform illness into wellness through the best of conventional medicine, functional medicine and integrative therapeutic options.