What’s the scoop on Vitamin D and COVID?
There are now several studies to suggest that it has a protective effect against severe COVID. This isn’t entirely surprising as Vitamin D has been shown to play a role in our immune system’s ability to respond and has shown to have a protective effect related to several illnesses. This blog will cover a recent study that came out of Israel.
What did they do?
The study in Israel was a retrospective study designed to assess the relationship, if any, between pre-infection levels of serum 25-hydroxyvitamin D and severity of disease and mortality. It’s easy to do retrospective studies in Israel because their electronic medical record system is robust. In this study, they looked at medical records of patients admitted to the Galilee Medical Center in Nahariya, Israel between April 7th’20 and February 4th’ 21 with a positive PCR test for COVID-19. Specifically they looked for their 25(OH)D levels measured 14-730 days prior to the positive PCR test. The researchers categorized the Vitamin D levels as deficient; insufficient; adequate; and high-normal.
What did they find?
Of 1176 patients admitted, 253 patients had a recorded 25(OH)D level prior to getting COVID-19. In general, a lower Vitamin D (<20 ng/ml) status was more common in patients with severe or critical disease (87.4%) than in individuals with mild/moderate disease (34.3%). This finding was statistically significant. Patients deficient in Vitamin D (Levels below 20 ng/ml) were 14 times more likely to have severe or critical disease than patients with 25(OH)D levels that were greater than 40 ng/ml. The study clearly showed that among hospitalized COVID patients during the designated time period, pre-infection levels of Vitamin D were significantly associated with disease severity and mortality.
What about age?
The strongest correlation between lower pre-infection Vitamin D levels and more severe COVID-19 was seen in patients over 50. In patients under 50, the relationship was still significant, but not as strong.
What about BMI?
Obesity has been shown to be an independent risk factor for more severe COVID-19. (You can listen to a Causes or Cures podcast I did with two researchers on this topic here.) It is also associated with lower Vitamin D levels. However, in this study, there was not a strong association between low Vitamin D levels and a patient’s BMI. (I want to note that I am fully aware that the BMI is not the best or most accurate measurement for obesity. It just happens to be the best, most cost-effective measure to use at the population level.)
Vitamin D and COVID: Why might it be preventive against COVID-19?
In the literature, low Vitamin D status has been linked to other infectious diseases, autoimmune disorders, poor bone health and cardiovascular issues. As shown in this systemic review
of 11 placebo-controlled trials, low levels of Vitamin D have been linked to a higher chance of getting the flu and other respiratory viruses, and that 1 dose a day seemed more protective than a bolus shot, although their results could have been influenced by publication bias and the heterogeneity of the trials. Lov Vitamin D levels has even been linked to some psychiatric disorders
. Lab studies show that Vitamin D can inhibit pro-inflammatory cytokines in various ways. One thing we hear a lot about in COVID-19 is the “cytokine storm” which is associated with more severe disease. Perhaps Vitamin D helps mitigate this.
Vitamin D deficiency is not uncommon. Risk factors include greater skin pigmentation, older age, low sun exposure, obesity, wearing head coverings and skin-covering clothes, and diets low in fish and dairy.
While this study has limitations (like all studies), one of its strengths is that it determined patients’ Vitamin D level PRIOR to them coming to the hospital. That’s a key temporal association, since Vitamin D levels may be impacted once a person gets sick. One question I have is if there was something unique about the proportion that had their Vitamin D levels measured. Were they sick? Curious? Are there any possible confounders there?
Should You Take a Vitamin D Supplement?
This is an interesting question. Usually, it’s good to actually measure the level of anything before you supplement. In the world of wellness, there is a tendency to just supplement with the idea that you are doing “good” for yourself and can’t possibly do any harm because the supplement is innocuous enough. The people selling the supplements know that and use it against you, by the way. That’s generally speaking about all supplements but going to the doctor or lab and getting your levels tested is a pain in the butt for a lot of people. Vitamin D is unique because our sun exposure affects our levels. Therefore, it is common sense to understand that it might be lower in colder/winter months vs summer months. (I supplement with Vitamin D in the fall-winter months, and no, I don’t measure my levels.) Reviews and meta-analyses of randomized controlled trials conducted between 2007 and 2020 showed that, compared to a placebo, supplementing with Vitamin D reduced the risk of acute respiratory infection. The authors of that study
commented that Vitamin D was safe overall but that the overall risk reduction was small. The protective effective was seen with daily doses of 400-1000 IU for up to a year. The authors also cautioned against applying those findings to COVID-19.
On Vitamin D and COVID specifically, there are studies that suggest supplementing with Vitamin D has a protective effect against getting infected with COVID-19 and getting a severe case. This review
does a great job outlining existing evidence. This study
was a retrospective study that looked at Vitamin D prescriptions in 15,968 hospitalized COVID-19 patients in Andalusia between Jan-Nov’20. Prescription with Vitamin D or its metabolites within 15-30 days before hospitalization was associated with better patient survival. The association was stronger for calcifediol than for cholecalciferol and the relationship was strongest when the prescription was given closer to the date of hospitalization.
There are studies that suggest it is too early to state that supplementing with Vitamin D will make a big difference in COVID-19 outcomes, because there are too many confounding factors. Meaning, the reasons someone might be deficient in Vitamin D are also independent risk factors for more severe COVID. A recent Cochrane review
by Stroehlein et al concluded that there was insufficient evidence to recommend Vitamin D supplementation for COVID-19. Finally, while trust in the government and traditional public health sources is on the decline, I think the NIH has a solid presentation
on Vitamin D that gets into the supplement issue more.
Vitamin D and COVID conclusion:
This is an interesting new study that adds to the body of evidence suggesting that low Vitamin D levels can lead to more severe cases of COVID-19. However, when it comes to the question of supplementing with Vitamin D as it relates specifically to affecting the outcomes of COVID-19, it may help, but more research is needed.