Effects of select dietary supplements on the prevention and treatment of viral respiratory tract infections: a systematic review of randomized controlled trials

ABSTRACT

Introduction: Viral respiratory tract infections (RTIs) have been recognized as a global public health burden. Despite current theories about their effectiveness, the true benefits of dietary supplements on the prevention and treatment of viral RTIs remain elusive, due to contradictory reports. Hence, we aimed to evaluate the effectiveness of dietary supplements on the prevention and treatment of viral RTIs.

Areas covered: We systematically searched databases of PubMed, Web of Science, Scopus, and Google Scholar through 4 March 2020, to identify randomized controlled trials that evaluated the effects of consuming selected dietary supplements on the prevention or treatment of viral RTIs.

Expert opinion: Thirty-nine randomized controlled trials (n = 16,797 participants) were eligible and included. Namely, vitamin D supplementation appeared to improve viral RTIs across cohorts particulate in those with vitamin D deficiency. Among the evaluated dietary supplements, specific lactobacillus strains were used most commonly with selected prebiotics that showed potentially positive effects on the prevention and treatment of viral RTIs. Further, ginseng extract supplementation may effectively prevent viral RTIs as adjuvant therapy. However, longitudinal research is required to confirm these observations and address the optimal dose, duration, and safety of dietary supplements being publicly recommended.

KEYWORDS:

• Viral respiratory tract infection
• dietary supplements
• COVID-19
• SARS-CoV-2
• systematic review

Article highlights

• Vitamin D supplementation (400 to 4000 IU/day) appears to improve the health outcomes with viral respiratory tract infections (RTIs) across cohorts particularly in those with vitamin D deficiency.

• Select lactobacillus strains (casei, paracasei, coryniformis, acidophilus, fermentum, plantarum, and rhamnosus) and prebiotics (short-chain fructooligosaccharides or galactooligosaccharides) are the most widely used dietary supplements with potentially positive effects on prevention treatment of viral RTIs.

• Yeast beta-glucan supplementation (250 to 900 mg/day) may be associated with decreased RTIs symptoms such as the number of days with the common cold or flu symptoms.

• Ginseng extract supplementation (400 to 3000 mg/day) may be useful in preventing vial RTIs.

Quercetin supplementation (500 to 1000 mg/day) may decrease the incidence and duration of upper respiratory tract infections.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was not funded.