African Americans are more susceptible to vitamin D deficiency. In addition they have lower amounts of cellular glutathione (GSH), which is an antioxidant produced in the body from L-cysteine, capable of affecting genes involved in vitamin D production. Clinical trials have indicated a relationship between vitamin D deficiency and poorer outcomes in patients with COVID-19. This review paper looked at data in humans, animal models and at the cellular level and proposed that African Americans are susceptible to vitamin D deficiency due to increased skin pigmentation affecting its production. Reduced GSH was attributed to decreased dietary intake of L-cysteine, and lower levels of biological compounds, which are involved in the production of GSH. Research surrounding vitamin D’s role in immunity and lowering viral infection risk was reviewed and several routes were proposed, such as increasing anti-microbial action, decreasing inflammation, increasing anti-oxidants and blocking viruses entering cells. It was concluded that randomised control trials on vitamin D supplementation have been underwhelming. This disconnect with trials showing a relationship between low vitamin D levels and poor clinical outcomes is due to the fact that vitamin D was tested in isolation. More randomised control trials are needed to investigate co-supplementation with L-cysteine on outcomes of COVID-19 infection in African Americans. Clinicians could use this review to understand the relationship between vitamin D and L-cysteine and, in lieu of any randomised control trials, as a potential justification for co- supplementation of Vitamin D and L-cysteine in patients with vitamin D deficiency and COVID-19.