Table 2.

Overview of vital functional food components (non-polyphenols) in boosting up the immune response, virus targeted, and functions related, quoted from (London, 2010; Maggini et al., 2018; Zhang & Liu, 2020).

Food components	Health properties	Virus targeted and related functions
Ʊ-3 fatty acids	•Stimulation of the immune system.	Influenza and human immunodeficiency virus.
Vitamin C	•Stimulates production, function, and movement of leukocytes (e.g., lymphocytes, neutrophils, and phagocytes). Antimicrobial, natural killer cell activities, and chemotaxis. Regenerates other important antioxidants such as glutathione and vitamin E to their active state. Promotes collagen synthesis. Increases serum levels of complement proteins. Involved in apoptosis and clearance of spent neutrophils from sites of infection by macrophages.	Avian coronavirus.
Vitamin D	•Stimulates immune cell proliferation and cytokine production and helps protect against infection caused by pathogens. Expressed in innate immune cells (e.g., monocytes, macrophages, dendritic cells).	Bovine coronavirus.
Vitamin A	•Maintains the structural and functional integrity of mucosal cells in innate barriers (e.g., skin, and respiratory tract).	Measles virus, human immunodeficiency virus, and avian coronavirus.
Vitamin B	•Boosting the immune response of the host.	MERS-CoV.
Vitamin E	•Impairs humoral and cell-mediated aspects of adaptive immunity, i.e., B and T cell function.	Coxsackievirus and bovine coronavirus.
Se	•Important for the antioxidant host defense system affecting leukocyte.	Influenza virus and avian coronavirus.
Fe	•Stimulation of the immune system.	Viral mutations.
Zn	•Stimulation of the immune system.	Measles and SARS-CoV.