For decades, olive oil has been treated as a hallmark of Mediterranean eating rather than a genuine clinical tool. Two of the largest nutrition trials ever run in Europe suggest that reputation is deserved.
The PREDIMED study followed more than seven thousand adults in Spain who were at high cardiovascular risk. Participants were randomly assigned to a low fat diet, a Mediterranean diet supplemented with nuts, or a Mediterranean diet supplemented with extra virgin olive oil at around fifty grams a day. The main results, published in the New England Journal of Medicine in 2013 and republished after a statistical correction in 2018, showed a meaningful reduction in cardiovascular events in both Mediterranean diet groups compared with the low fat group.
A smaller arm of the same trial, run specifically in the Spanish city of Reus and published in Diabetes Care in 2011, asked a more specific question: could this way of eating prevent type 2 diabetes in people who did not yet have it. Over four years, diabetes incidence was 10.1 percent in the Mediterranean diet with olive oil group compared with 17.9 percent in the low fat group, a difference the researchers described as clinically meaningful even without participants losing weight or increasing exercise.
The likely mechanism sits in the fat itself. Extra virgin olive oil is rich in monounsaturated fat and polyphenols, plant compounds that appear to support insulin sensitivity and reduce the glucose spike that follows a carbohydrate containing meal. Several smaller crossover trials have shown that adding olive oil to a meal blunts the rise in blood glucose that would otherwise follow, particularly when the oil is extra virgin rather than refined.
None of this means olive oil works in isolation. In every trial, it was consumed as part of a broader pattern that included vegetables, legumes, and minimal processed food. What the evidence does support is that the type of fat on your plate is not a minor detail. Swapping refined and processed oils for a genuine extra virgin olive oil, and using it generously rather than sparingly, is one of the more evidence backed changes available to anyone working on blood sugar control.
References
- 1. Estruch R, Ros E, Salas Salvado J, et al. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med. 2013;368(14):1279 to 1290 (republished N Engl J Med. 2018;378(25):e34).
- 2. Salas Salvado J, Bullo M, Babio N, et al. Reduction in the incidence of type 2 diabetes with the Mediterranean diet: results of the PREDIMED Reus nutrition intervention randomized trial. Diabetes Care. 2011;34(1):14 to 19.
- 3. Violi F, Loffredo L, Pignatelli P, et al. Extra virgin olive oil use is associated with improved post prandial blood glucose and LDL cholesterol in healthy subjects. Nutr Diabetes. 2015;5(7):e172.
