Exploring Galician phenolic-rich olive oil as a glycemic control strategy: the OILDIABET randomized trial

The rising prevalence of type 2 diabetes (T2D) demands effective dietary strategies. High-phenolic extra virgin olive oil (EVOO) has been proposed as a functional food with antidiabetic properties. This study evaluates the effects of a high-phenolic EVOO from native Galician olives on glycemic control (primary outcome), lipid profile, anthropometric and blood pressure parameters (secondary outcomes) in adults with T2D. A 24-week experimental, prospective, randomized, parallel, long-term controlled trial was conducted with 116 T2D subjects. Participants were randomly allocated either to a Control group advised to minimize consumption of EVOO (preferring refined olive oil blends) or an Interventional group receiving 30 mL day^-1 of Galician phenolic-rich EVOO. Glycemic biomarkers, lipid profile, anthropometric indices, and blood pressure were assessed at baseline, 12 and 24 weeks. After 24 weeks, the Interventional group demonstrated significant reductions in insulin resistance (HOMA IR). No significant changes were observed in lipid profile or blood pressure in either group, while both groups exhibited modest reductions in body weight and body mass index (BMI). Although beneficial effects were particularly pronounced among individuals with obesity (reductions in fasting glucose, estimated average glucose and glycosylated hemoglobin (HbA1c)) and insulin-resistant participants (reductions in fasting insulin and HOMA IR), these subgroup analyses lacked sufficient statistical power and must be interpreted cautiously. These findings highlight the therapeutic potential of phenolic-rich EVOOs as a complementary dietary strategy for managing T2D.