Vitamin D is a fat soluble vitamin found in only a handful of foods and primarily synthesized in the body from sun exposure. Vitamin D aids in calcium absorption, bone growth, and bone remodeling [i]. It also reduces inflammation and plays a role in glucose metabolism, cell growth, neuromuscular function, and immune function [Institute of Medicine, Food and Nutrition Board, 2010; Norman & Henry, 2012; Jones, 2014 as cited in reference i]. Low vitamin D levels may increase risk of osteoporosis, diabetes, cancer, cardiovascular disease, autoimmune diseases, infectious diseases, dental caries, and periodontal disease [i; Anbarcioglu et al., 2019; Uwitonze et al., 2018 as cited in reference ii]. The below study looks at the association between vitamin D deficiency and COVID-19 and considers possible confounding variables.
This cross-sectional retrospective study involved 887 participants from the University of Florida i2b2 patient registry platform which included patient visits from a number of University of Florida health centers. Researchers searched the registry platform for diagnostic codes for vitamin D deficiency, diabetes, obesity, malabsorption, caries, periodontal disease, and periapical abscesses from October 1, 2015 to June 30, 2020, and COVID-19 in the year 2020 before June 30, 2020 [ii].
The authors found:
1. Those with vitamin D deficiency were 4.6 times more likely to be positive for COVID-19
2. The association between vitamin D deficiency and COVID-19 decreased slightly when adjusting for sex, malabsorption, periapical abscesses, and caries
3. The association between vitamin D deficiency and COVID-19 decreased significantly but remained robust when adjusting for race, periodontal disease, diabetes, and obesity
4. After adjusting for age, those with vitamin D deficiency were 5 times more likely to be positive for COVID-19 [ii]
For the Patient and Caregiver
Although additional research is needed on vitamin D supplementation for preventing and treating COVID-19, you may consider adding vitamin D rich foods into your eating pattern. These include salmon, mushrooms, fortified milks and dairy free milks, and fortified breakfast cereals. Less commonly consumed is cod liver oil, with 1 tablespoon containing 170% of the daily value of vitamin D [i]. The next time you have your annual physical, you may want to ask your provider to check your vitamin D levels to determine if supplementation is appropriate.
For the Healthcare Team
Determine if checking vitamin D levels is indicated, which may include for those with obesity or a history of bariatric surgery, malabsorptive conditions, limited sun exposure, darker skin, or for those who are older adults [i]. Recommend supplementation based on labs, and encourage intake of foods that naturally have or are fortified with vitamin D. Of note, this study did not include information on severity of COVID-19, treatment, or length of vitamin D deficiency in the individuals, which are important considerations for future research. Further studies are also needed to determine appropriate recommendations for vitamin D supplementation in COVID-19 prevention and treatment.
[i] Vitamin D Fact Sheet for Health Professionals. National Institutes of Health Office of Dietary Supplements. Retrieved from https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
[ii] Katz J, Yue S, Xue W. (2021). Increased risk for COVID-19 in patients with vitamin D deficiency. Nutrition, 84. https://doi.org/10.1016/j.nut.2020.111106