Preventive medicine over the last decade has gone to great extents; this is particularly so in developed countries. Various research studies have confirmed that nutrition has a great relationship with the prevention and control of long-term diseases mainly attributed to diet. Food is considered the best provider to ensure our healthiness. Food also prevents and cures several diseases and improves particular physiological functions. The components of diet are qualified as functional foods, providing the body not only with nutrients and energy but also helping its system regulate special functions by either improving physiological processes or reducing the potential of the disease. Since the FFC recommends research and usage of functional foods in the treatment of chronic diseases, this review will illustrate the use of functional meals in the treatment of various viral diseases. From this study, we shall expect to suggest an improvement to the present definition of functional foods to comprise this added use. It covers many influences of functional foods and minerals on immunological function, such as probiotics, dietary antioxidants that include vitamins C, A, and E, and selenium. However, the desirable intake level and quantities of consumption of functional foods are yet developed. Therefore, more research studies are needed that would eliminate controversy over functional food. And our works must be absolutely placed toward gaining the highest objective of a ";;;functional diet";;;.