Table 1.

Features of the studies published on EVOO and MedDiet beneficial effects.

Author/Year	Design of the Study	Drug	Outcome(s)	Conclusion
Fuentes et al. [71], 2001	Intervention dietary study Patients n°: 22	Low-saturated fat diet vs. MedDiet	Determine endothelial function in hyper-cholesterolemic patients in the two different diets	Flow-mediated dilatation increased during the MedDiet levels of plasma cholesterol, LDL, ApoB and P-selectin decreased with both diets
Esposito et al. [53], 2004	Randomized, single-blind trial Patients n°: 180 with metabolic syndrome (MetS)	MedDiet vs. Control diet	Nutrient intake endothelial function score lipid and glucose parameters, insulin sensitivity and circulating levels of hs-CRP and interleukins 6 (IL-6), 7 (IL-7) and 18 (IL-18).	Body weight and hs-CRP decreased Endothelial function score improved The number of patients with metabolic syndrome decreased
Mitjavila et al. [83], 2012	Randomized, controlled, trial Patients n°: 110 with MetS	MedDiet + EVOO 1Lt/week or MedDiet + mixed nuts vs. Low-fat diet	Test the efficacy of MedDiet on the primary prevention of cardiovascular diseases	MedDiet reduces oxidative damage to lipids and DNA in MetS individuals
Loued et al. [57], 2013	Interventional study Patients n°: 20 healthy subjects (divided in two groups: 10 young and 10 elderly)	EVOO 25 mL/day administered to the two groups	Investigate the effect of ageing and the role of PON1 on the anti-inflammatory activity of HDL Determine whether EVOO consumption could improve the atheroprotective activity of HDL	EVOO consumption increased the anti-inflammatory activities of both HDL and PON1 The anti-inflammatory activity of HDL was modulated by PON1 and was lower in the elderly volunteers EVOO consumption increased the anti-inflammatory effect of HDL and reduced the age-related decrease in anti-atherogenic activity
Carnevale et al. [82], 2014	Randomized controlled trial Patients n°: 25 healthy subjects	MedDiet with EVOO 10 gr/day vs. MedDiet without EVOO	Investigate the role of EVOO in the atherosclerotic process	Addition of EVOO to a MedDiet protects against postprandial oxidative stress
Salas-Salvadó et al. [54], 2014	Randomized controlled trial Patients n°: 3541 without diabetes at high cardiovascular risk	MedDiet supplemented with EVOO vs. MedDiet supplemented with nuts vs. Control diet (advice on a low-fat diet)	Assess the efficacy of MedDiet for the primary prevention of diabetes	MedDiet supplemented with EVOO reduced diabetes risk among persons with high cardiovascular risk
Violi et al. [84], 2015	Interventional cross-over study Patients n°: 25 healthy subjects	MedDiet with EVOO 10 gr/day vs. MedDiet without EVOO	Find the mechanisms that make EVOO effective in the prevention of cardiovascular disease	Decrease in blood glucose, DPP-4 protein and activity, LDL-C, oxLDL Increase in insulin, GLP-1, GIP
Santangelo et al. [55], 2016	Interventional study Patients n°: 11 with T2DM, overweight but non-insulin treated	Abutal diet supplemented with EVOO 25 mL/day	Improvement in anthropometric parameters, fasting glycaemia, HbA1c, high-sensitive CRP, plasma lipid profile, liver function and serum levels of TNF-α, IL-6, adiponectin, visfatin.	EVOO significantly reduced fasting plasma glucose, HbA1c, BMI, and body weight, serum levels of AST and ALT and serum visfatin levels
Carnevale et al. [87], 2017	Interventional cross-over study Patients n°: 30 with IFG	Meal with 10 gr of EVOO vs. Meal without EVOO	Improvement in postprandial glycaemia	EVOO reduces glycemia and DPP-4 activity Increases insulin and GLP-1 and decreases triglycerides and Apo B
Marrano et al. [68], 2021	In vitro study	INS-1E cells were exposed to 10 μM of the main EVOO PCs for up to 24 h	To investigate the effects of several phenolic compounds (PCs) on beta-cell function and survival	EVOO may improve insulin secretion and promote glycaemic control in T2DM patients
Bartimoccia et al. [93], 2022	Interventional study Patients n°: 20 with IFG and 20 healthy subjects	Mediterranean-type meal with 10 gr of EVOO vs. Mediterranean-type meal without EVOO	Improvement in postprandial glycaemia by reducing gut permeability-derived low-grade endotoxemia	IFG patients assuming EVOO showed a less significant increase in blood glucose, blood insulin and GLP1 and a significant reduction in LPS and zonulin compared to IFG patients not given EVOO

Apolipoprotein B (ApoB); dipeptidyl peptidase-4 (DPP-4); extra virgin olive oil (EVOO); glucagon-like peptide 1 (GLP1); high-sensitivity C-reactive protein (hs-CRP); impaired fasting glucose (IFG); Mediterranean diet (MedDiet); metabolic syndrome (MetS); paraoxonase 1(PON1); type 2 diabetes mellitus (T2DM).