Could Vitamins Help in the Fight Against COVID-19?

Abstract

There are limited proven therapeutic options for the prevention and treatment of COVID-19. The role of vitamin and mineral supplementation or "immunonutrition" has previously been explored in a number of clinical trials in intensive care settings, and there are several hypotheses to support their routine use. The aim of this narrative review was to investigate whether vitamin supplementation is beneficial in COVID-19. A systematic search strategy with a narrative literature summary was designed, using the Medline, EMBASE, Cochrane Trials Register, WHO International Clinical Trial Registry, and Nexis media databases. The immune-mediating, antioxidant and antimicrobial roles of vitamins A to E were explored and their potential role in the fight against COVID-19 was evaluated. The major topics extracted for narrative synthesis were physiological and immunological roles of each vitamin, their role in respiratory infections, acute respiratory distress syndrome (ARDS), and COVID-19. Vitamins A to E highlighted potentially beneficial roles in the fight against COVID-19 via antioxidant effects, immunomodulation, enhancing natural barriers, and local paracrine signaling. Level 1 and 2 evidence supports the use of thiamine, vitamin C, and vitamin D in COVID-like respiratory diseases, ARDS, and sepsis. Although there are currently no published clinical trials due to the novelty of SARS-CoV-2 infection, there is pathophysiologic rationale for exploring the use of vitamins in this global pandemic, supported by early anecdotal reports from international groups. The final outcomes of ongoing trials of vitamin supplementation are awaited with interest.

Keywords: COVID-19; SARS-CoV-2; immunonutrition; supplementation; vitamin.

Figure 1

Systematic search strategy flow diagram.

Figure 2

Number of newspaper articles published on vitamin supplementation in COVID-19 over time.

Figure 3

Chemical structure of vitamin A, retinol.

Figure 4

Retinoic acid and carotenoids exert a number of physiological effects, including the augmentation of T cell function, which may improve the adaptive immune response to pathogens, such as viruses. Furthermore, antioxidant and surfactant-mediating properties of vitamin A derivatives may have a protective role in the pathogenesis of ARDS, a known complication of severe cases of COVID-19.

Figure 5

Thiamine and its derivatives act synergistically with ascorbic acid to reduce anaerobic respiration and reduce oxidative stress. It has been suggested this combination may improve mortality and organ recovery in critically ill patients with septic shock through vasoactive effects, bacteriostatic action, and immune cell mediation. The significance of these actions on viral infections, such as COVID-19, remain to be elucidated.

Figure 6

Chemical structure of vitamin C, ascorbic acid.

Figure 7

Chemical structure of vitamin D3, cholecalciferol.

Figure 8

Vitamin D and potential anti-COVID19 mechanisms of action. Vitamin D derivatives are thought to mediate the immune system responses to infective agents through enhanced Treg and Th2 cell function, attenuating the cytokine storm that is thought to be a key pathogenic mechanism in ARDS. Other speculated roles include the protection against lung injury through modulating the pulmonary renin-angiotensin system and reducing viral entry and replication.

Figure 9

Chemical structure of vitamin E, (2′R, 4′R, 8′R)-tocopherol.

Figure 10

Vitamin E and potential anti-COVID19 mechanisms of action in ARDS. The antioxidant properties of Vitamin E derivatives may augment cell membrane integrity and improve the adaptive immune system response to viral respiratory tract infections.