Vitamin D is essential for normal human functioning, but just how much is necessary has been a subject of debate and whether supplementing vitamin D in people who have “normal” levels can be beneficial in the prevention or treatment of certain diseases has been a subject of controversy for decades, largely due to the lack of high-quality studies.
While some will argue that the level of normal vitamin D should be set higher than current guidelines, I think that you would find a general consensus that an adult is vitamin D deficient if their serum 25-hydroxyvitamin D level is < 50 nmol/L or 20 ng/ml. There would also likely be agreement that treatment with vitamin D supplementation in individuals with serum 25-hydroxyvitamin D levels of < 30 nmol/L or 12 ng/ml is beneficial and very important for overall health.
Many people promoted the need for vitamin D supplementation to prevent and/or treat COVID-19 when the pandemic first began (in fact, a number of people continue to promote this idea). Unfortunately, we had little data or clinical studies at that time to answer that question. However, two years later, we know a lot more. Here are some key points:
- A study from Italy showed that a low serum vitamin D level was an independent risk factor for developing severe COVID-19 (mean 18.2 ng/ml) and dying (mean 13.2 ng/ml) from it, if a patient with low vitamin D gets infected.
- Unfortunately, studies have not been able to demonstrate that giving high doses of vitamin D once the patient with low vitamin D gets infected will reverse the risks for severe disease, hospitalization, the need for intensive care, mechanical ventilation or death.
- Some persons have a genetic abnormality that causes them to have high levels of vitamin D, but studies have demonstrated that these folks do not have a lower risk of getting infected or if infected, having less severe disease or risk of hospitalization and death.
Guidelines from the Endocrine Society recommend the following dietary intake of vitamin D:
- Children aged 1-18 years: ≥ 600 IU/d
- Adults aged 19-70 years: ≥ 600 IU/d
- Adults older than 70 years: ≥ 800 IU/d
So, above, I have provided you with the state of the science. But now, here are my thoughts and how I put all this together:
- If you have vitamin D deficiency, it makes sense to take a daily vitamin D supplement. My vitamin D levels have been low and I take a daily supplement. If you have low levels of vitamin D, you may be at higher risk if infected.
- The fact that people with low vitamin D levels are at increased risk for severe disease if infected, but supplementing with vitamin D once infected doesn’t improve outcomes, as well as the fact that those with high vitamin D levels are not protected from developing severe disease suggests to me that vitamin D is likely only one factor in this risk for severe disease and may not even be the most important factor. Thus, if you get infected, please don’t rely on vitamin D and other supplements to keep you from getting severely ill. Seek medical attention from a physician and explore options that have been proven to improve outcomes if you are at high risk for severe disease, such as antiviral medications and monoclonal antibodies. I have no objection to taking vitamin D if you get infected, my point is simply that you should not rely on vitamin D or any other supplements to keep you from getting severely ill.