Unraveling the Extra Virgin Olive Oil Effect on Inflammation and on Gut and Saliva Microbiota

Extra virgin olive oil (EVOO) with a high content of polyphenols has attracted attention due to its proved beneficial effects in decreasing the risk of cardiovascular disease, modulating cholesterol levels (HDL and LDL), modulating inflammatory markers, and decreasing the levels of haemoglobin1Ac, suggesting that EVOO can have an impact in glycemia regulation. This study assessed the impact of the consumption of a northern Portuguese polyphenol-rich EVOO with a high profile of bioactive molecules on several parameters, such as saliva and serum inflammatory biomarkers, and explored EVOO impact on gut and oral microbiota regarding Bacillota and Bacteroidota content. Thus, the impact on glycated haemoglobin (HbA1c), low-density lipoprotein cholesterol (LDL-C), C-reactive protein (CRP), inflammatory biomarkers, and faecal and salivary microbiomes were evaluated before and after the exposure to EVOO. The results showed that EVOO promotes a decrease in the levels of HbA1C and in the pro-inflammatory interleukin IL-1β, associated with inflammatory processes. Moreover, EVOO intake modulated gut and oral microbiota, increasing Bacteroidota in both ecological niches and Bacillota in the oral microbiota, both phyla being associated with health, demonstrating a prebiotic effect.