Nutrition and immunomodulation – focus on the dietary fiber RG-I – Rhamnogalacturonan-I trains the immune system and accelerates immune responses

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INTRODUCTION
A healthy immune system is a resilient system that manages daily challenges while maintaining responsiveness within a normal range and minimizing the notable impact of infections (1). Factors that can negatively impact the resilience of the immune system include ageing, an unhealthy diet and lifestyle, malnutrition, (chronic) illness, and medication (e.g., antibiotics). Good nutrition is one of the key factors that can positively influence the immune system. A nutritious diet provides a balanced supply of (micro)nutrients and is essential for maintaining health. While vitamins A, B6, B12, C, D, E, folate and zinc, copper, selenium, and iron support the normal function of the immune system (2–15), other food components and especially specific (non-digestible) dietary fibers can play an important role in the education and regulation of immune responses, both locally in the gut and beyond the gut in the rest of the body (16–18). Everything that is eaten is sampled by immune cells located in and around the small intestine, recognition of specific ‘patterns’ can result in priming or training and subsequent modulation of immune responsiveness (19).
The sort of food that is eaten also influences the composition and function of the gut microbiota, e.g., dietary fibers increase the abundance of beneficial microorganisms which can lead to the production of active metabolites like short chain fatty acids (SCFA) (17).