In lieu of a vaccine, complementary therapies have a major role to play in the Covid-19 pandemic. This review paper aimed to highlight how lifestyle approaches such as consumption of functional foods and increased physical activity could optimise the immune system in response to viral infections such as respiratory tract infections and Covid-19, and act as a possible adjuvant to vaccination. The paper outlined the role of exercise as being controversial. Although exercise has been shown to activate white blood cells, intense exercise in elite athletes has been linked to higher upper respiratory tract infection rates. It appears that varying intensity and type of exercise may optimise the immune system and have an additive effect to immunisation against viruses like influenza. The authors also stated that having a sedentary lifestyle may impair the immune system and diseases such as obesity and diabetes may increase susceptibility to infections such as Covid-19. The antiviral effect of functional foods was discussed. The paper paid particular attention to olive oil, vitamin D, traditional herbs and roots, coffee and caffeine. The reviewed mechanisms included enhanced gut bacteria profiles and promotion of anti-oxidants and anti-inflammatories. The authors also stated that supplementation as well as adequate dietary intake might be of importance against Covid-19, especially in deficient individuals. It was concluded that moderate intensity exercise alongside dietary intake of functional foods, may prevent communicable diseases, such as Covid-19. Clinicians could use this paper to recommend specific functional foods plus moderate exercise, to help prevent viral infections like Covid-19.