Diet can influence the diversity and abundance of gut microbiota; therefore, the gut microbiome is considered a therapeutic target for management of certain diseases.14 Nutritional strategies (such as the use of probiotics and prebiotics) that attempt to selectively increase the population of beneficial microbes continue to be explored.
Probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host. They are frequently delivered in dairy foods, capsules or liquid formations.14,15 Probiotic products contain microbial strains which supports immunological stimulation by increasing production of immunoglobulins and enhancing the activity of immune cells.14,16 The efficacy of probiotics depends on the strain, dose, and ingredients used to produce the probiotic product.16 Probiotic products are considered safe, however high-risk populations including those who are critically ill or are immunosuppressed should use probiotics with caution.17 Despite progress having been observed, there are currently no approved health claims for probiotics in the UK.18
Prebiotics are ingredients selectively used by host microorganisms that confer a health benefit.15 Dietary fibre is a source of prebiotics and fibre-rich diets have well-documented beneficial health effects. For example, galactooligosaccharides (GOS) are a source of prebiotics that can increase abundance of Bifidobacterium, which help to prevent colonisation of pathogens.14 Supplementation with a synthesised form of GOS, was found to increase SIgA which resulted in improved immune function (e.g. alterations in c-reactive protein, calprotectin).14 Dietary sources of GOS include cereals, legumes and vegetables including onion and garlic.19 Dietary polyphenols which occur in vegetables, fruit and extra virgin olive oil have been shown to exert antimicrobial effects against pathogenic bacteria.20
Current evidence suggests that a fibre-rich plant-based diet containing wholegrains, fruit and vegetables, nuts and seeds, beans and pulses can help to promote a diverse gut microbiome. Indeed, results from the American Gut Project found that people who consumed more than 30 different types of plants each week had more diverse gut microbiomes compared to those who consumed 10 or fewer types. Nutritional strategies aimed at the modification of the gut microbiome requires further evidence to determine if this a feasible approach in the prevention and treatment of immunological diseases.