Nutrition plays an important role in the immune system by providing energy and metabolites to support the function of immune cells, allowing them to initiate effective immune responses. Diet is therefore a modifiable factor in impacting immune function and is currently a topic of substantial interest in health research. Snack consumption has been shown to account for approximately 20-30% of daily energy intake in adults. Therefore, snack choices have the potential to influence dietary intake and quality, and therefore immune function, both positively and negatively. This study assesses the effect of replacing usual snacks with alternative snack foods on the immune response in a model of viral infection - the seasonal influenza vaccine containing four prevalent influenza virus strains for the 2022/23 influenza season, as determined by the World Health Organization.~This study is a parallel group, randomised controlled trial that will examine the replacement of usual snack foods with alternative snack foods on the immune response to seasonal influenza vaccination in humans, which will be assessed by measuring rates of seroconversion, and other immunological markers following vaccination. The intervention will be for 8 weeks, and influenza vaccination will be administered at 4-week midpoint. Participants will be followed up 3 months post-vaccination to assess incidence of upper respiratory symptoms.
The purpose of this study is to evaluate the impact of replacing usual snacks with alternative snack foods on the immune response to influenza vaccination in a population of healthy, middle-aged adults.