Supplement Snapshot: Vitamin D and Respiratory Tract Infections

Pharmacists are frequently consulted about dietary supplements, none more so than vitamin D, which remains the most popular after multivitamins.¹ Nearly half of Americans are deficient in vitamin D.² Because this vitamin is primarily produced through sun exposure rather than dietary factors, supplements offer a convenient, safe, and affordable way to address this public health issue. However, because these supplements are increasingly used for general health maintenance and to manage various medical conditions, consumers must understand the scientific evidence—or lack thereof—to use these supplements effectively.

Vitamin D capsules / Cozine - stock.adobe.com

One area where more clarity is needed is the use of these supplements for respiratory tract infections (RTIs). Although it is widely believed that vitamin D supplements can lower the risk and severity of RTIs and strengthen immunity, supported by evidence that suggests vitamin D may have immunomodulatory and anti-inflammatory effects,³ randomized controlled trials have produced inconsistent results.

Authors of a narrative review published in the Journal of the American Pharmacists Association put it plainly: “There is no evidence that vitamin D is effective in the prevention or treatment of tuberculosis, pneumonia, upper respiratory tract infections, or infections with SARS-CoV-2.”⁴ Other studies— although often limited by methodological issues—have suggested potential benefits: A recent meta-analysis contradicted the previous review. After analyzing 46 randomized controlled trials involving over 75,000 participants, investigators found that vitamin D supplementation was generally safe and associated with a small reduction in the risk of acute respiratory infections, but investigators noted evidence of significant heterogeneity across trials that could have affected results.⁵

Given these conflicting data, more research is needed to fully understand the role of vitamin D in RTIs. Acute respiratory infections are common, and are a leading cause of morbidity and mortality worldwide. Understanding vitamin D’s role in RTIs may inform clinical practice and reduce their burden.⁶

While research continues, pharmacists can still provide valuable counseling to patients.

Read on for some counseling tips on this popular supplement.

• The National Academy of Medicine recommends a daily intake of 600 IU of vitamin D for individuals aged up to 70 years and a daily intake of 800 IU in those aged about 70 years. Serum 25-hydroxyvitamin D levels of less than 12 ng/mL indicate a vitamin D deficiency.⁴
• Excessive intake of vitamin D can lead to adverse events, such as increased falls, fractures, and accelerated bone loss.4 Stay mindful of these potential outcomes when counseling patients—especially older adults, who are more susceptible to weaker bones—about using vitamin D supplements.⁷
• In a randomized trial of long-term care residents, those receiving a high-dose vitamin D supplement experienced fewer acute upper RTIs than the low-dose group. However, these individuals also experienced a higher risk of falls.⁸
• Emerging evidence suggests that vitamin D may mitigate the severity of COVID-19 infections. A review analyzed 58 clinical studies investigating the therapeutic effects of vitamin D in more than 14 million individuals with COVID-19.⁹ A majority—96%—of those studies showed that having higher levels of vitamin D were associated with less severe COVID-19 symptoms.
• Four studies included in that review supported the role of vitamin D in alleviating symptoms of post–COVID-19 condition (PCC). Per investigators, “There are promising reasons to enhance research on the effects of vitamin D supplements” in patients with PCC.
• Research on the relationship between vitamin D supplementation and COPD is limited. However, 1 study found a connection between low vitamin D levels and an increased risk of acute COPD exacerbations, in even patients who regularly spend time outdoors,¹⁰ suggesting that vitamin D deficiency may be a contributing factor for patients with COPD.

“Given the significant amount of conflicting data, it is difficult for most generalist practitioners to keep pace with the evidence,” wrote the review authors.⁴ “Pharmacists are in a position to provide patients with evidence-based recommendations concerning the indications, dosing, adverse effects, and drug interactions with vitamin D supplements.”

READ MORE: Respiratory Resource Center

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References

1. Mishra S, Stierman B, Gahche JJ, Potischman N. Dietary supplement use among adults: United States, 2017-2018. National Center for Health Statistics. Updated February 19, 2021. Accessed September 10, 2024. https://www.cdc.gov/nchs/products/databriefs/db399.htm

2. Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res. 2011;31(1):48-54. doi:10.1016/j.nutres.2010.12.001

3. Athanassiou L, Mavragani CP, Koutsilieris M. The immunomodulatory properties of vitamin D. Mediterr J Rheumatol. 2022;33(1):7-13. doi:10.31138/mjr.33.1.7

4. Awadh AA, Hilleman DE, Knezevich E, Malesker MA, Gallagher JC. Vitamin D supplements: the pharmacists’ perspective. J Am Pharm Assoc (2003). 2021;61(4):e191-e201. doi:10.1016/j.japh.2021.02.002

5. Jolliffe DA, Camargo CA Jr, Sluyter JD, et al. Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomised controlled trials. Lancet Diabetes Endocrinol. 2021;9(5):276-292. doi:10.1016/S2213-8587(21)00051-6

6. GBD 2016 Lower Respiratory Infections Collaborators. Estimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory infections in 195 countries, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet Infect Dis. 2018;18(11):1191-1210. doi:10.1016/S1473-3099(18)30310-4

7. Häder A, Köse-Vogel N, Schulz L, et al. Respiratory infections in the aging lung: implications for diagnosis, therapy, and prevention. Aging Dis. 2023;14(4):1091-1104. doi:10.14336/AD.2023.0329

8. Ginde AA, Blatchford P, Breese K, et al. High-dose monthly vitamin D for prevention of acute respiratory infection in older long-term care residents: arandomized clinical trial. J Am Geriatr Soc. 2017;65(3):496-503. doi:10.1111/jgs.14679

9. Gomaa AA, Abdel-Wadood YA, Thabet RH, Gomaa GA. Pharmacological evaluation of vitamin D in COVID-19 and long COVID-19: recent studies confirm clinical validation and highlight metformin to improve VDR sensitivity and efficacy. Inflammopharmacology. 2024;32(1):249-271. doi:10.1007/s10787-023-01383-x

10. Lokesh KS, Chaya SK, Jayaraj BS, et al. Vitamin D deficiency is associated with chronic obstructive pulmonary disease and exacerbation of COPD. Clin Respir J. 2021;15(4):389-399. doi:10.1111/crj.13310