FIGURE 4.

Overview of the impact of a balance diet versus western diet on gut microbiota and immune system and potential roles of interventions such as prebiotics, probiotics and synbiotics on microbiota-immune axis. In general, a balance diet modulates gut immune system directly or indirectly through gut microbiota with a mix of pro- and anti-inflammatory signals so that the immune system stays alert to keep its defenses but also remain tolerant to unnecessary signals to avoid needless inflammation (A). The pro-inflammatory components in western diet including low-quality fats (trans fatty acids and refined oils), refined carbohydrates (sugar and refined grains), unhealthy additives, processed red meat and salts directly modulate the immune system or negatively impact gut microbiota, causing dysbiosis and changes in metabolites leading to a leaky gut. Consequently, the gut immune homeostasis is shifted toward local or systemic chronic inflammation (B). Different interventions like prebiotics, probiotics and synbiotics can potentially amend dysbiosis and gut barrier integrity by promoting healthy gut microbiota and conferring their anti-inflammatory effects on immune system to restore gut immune homeostasis (C).