Plain language summary
A healthy immune system is one of the most important weapons in relation to the current pandemic of COVID-19 where no effective preventive and curative medicine is available. The main aim of this study was to evaluate the evidence on enhancing immunity in viral infections. This review focuses on influenza-like viral infections; however, other studies on viral infections have also been included. It included 43 articles of which 13 were on vitamins, 8 on minerals, 18 on nutraceuticals and 4 on probiotics. Results indicate that: - vitamin supplementation, especially vitamin D may be beneficial in people who are either deficient or insufficient. - adverse effects of vitamin E supplementation on the immune response have been reported. - there are several beneficial nutraceuticals, however their efficacy and safety depend on their ingredients, as well as various other factors including, methods of extraction. - in addition to basic hygienic practices, proper dietary and lifestyle behaviours are essential for prevention and treatment of respiratory viral diseases. Authors conclude that achieving recommended amounts of calories and micronutrient will be a challenge and elective micronutrient supplementations may be beneficial especially for vulnerable populations such as the elderly.
BACKGROUND AND AIMS Balanced nutrition which can help in maintaining immunity is essential for prevention and management of viral infections. While data regarding nutrition in coronavirus infection (COVID-19) are not available, in this review, we aimed to evaluate evidence from previous clinical trials that studied nutrition-based interventions for viral diseases (with special emphasis on respiratory infections), and summarise our observations. METHODS A systematic search strategy was employed using keywords to search the literature in 3 key medical databases: PubMed®, Web of Science® and SciVerse Scopus®. Studies were considered eligible if they were controlled trials in humans, measuring immunological parameters, on viral and respiratory infections. Clinical trials on vitamins, minerals, nutraceuticals and probiotics were included. RESULTS A total of 640 records were identified initially and 22 studies were included from other sources. After excluding duplicates and articles that did not meet the inclusion criteria, 43 studies were obtained (vitamins: 13; minerals: 8; nutraceuticals: 18 and probiotics: 4). Among vitamins, A and D showed a potential benefit, especially in deficient populations. Among trace elements, selenium and zinc have also shown favourable immune-modulatory effects in viral respiratory infections. Several nutraceuticals and probiotics may also have some role in enhancing immune functions. Micronutrients may be beneficial in nutritionally depleted elderly population. CONCLUSIONS We summaries possible benefits of some vitamins, trace elements, nutraceuticals and probiotics in viral infections. Nutrition principles based on these data could be useful in possible prevention and management of COVID-19.