Post-prandial Effects of Extra Virgin Olive Oil on Endothelial Function in Adults at Risk for Type 2 Diabetes

Diabetes is a public health problem of epidemic proportions. According to the 2017 National Diabetes Statistics Report, 30 million people, or 9.4% of the U.S. population, are estimated to have diabetes, of which 23.1 million people are diagnosed. About 84.1 million people, or 1 in 3 people in the U.S., are estimated to have prediabetes, yet only 1 out 10 people with prediabetes is aware that they have this condition. Of those with prediabetes, 15-30% are likely to develop Type 2 diabetes within 5 years. The total medical costs and lost work and wages for people with diagnosed diabetes is about $245 billion, with the medical costs for people with diabetes being twice as high as for those without diabetes. The risk of death in individuals with diabetes is more than 50% higher than for adults without diabetes. Type 2 diabetes accounts for about 90% to 95% of all diagnosed cases of diabetes. Diabetes is the seventh leading cause of death in the U.S. Diabetes complications include cardiovascular disease (CVD), stroke, hypertension, blindness, kidney disease, nervous system damage, limb amputations, and biochemical imbalances that can cause acute life-threatening events. Rates of cardiovascular mortality are 2 to 4 times higher among adults with diabetes than among those without diabetes.

Epidemiological and cohort studies show a clear and consistent correlation of hyperglycemia with CVD. High glucose activates a pro-atherogenic phenotype in the vessel wall of endothelial cells, vascular smooth muscle cells, inflammatory cells, fibroblasts, and platelets, leading to a feed-forward atherogenic response. Diets with a low glycemic load have been reported to improve serum lipid profiles, reduce C-reactive protein (CRP) levels, and aid in weight control. In cross-sectional studies, they have been associated with higher levels of high-density lipoprotein cholesterol (HDL-C), with reduced CRP concentrations, and, in cohort studies, with decreased risk of developing diabetes and CVD. Insulin resistance may also contribute to high blood pressure, increased triglycerides and LDL cholesterol, and reduced levels of HDL cholesterol. While glycemic control remains a cornerstone of diabetes care, the co-management of hypertension, atherosclerosis, cardiovascular risk reduction, and prevention of long-term consequences are also recognized as essential to improve long-term survival.

The cornerstone of the management and prevention of Type 2 diabetes is lifestyle intervention. Prior studies have shown an association between improvement in cardio-metabolic health and diets rich in olive oils. Low glycemic index foods are typically recommended for patients with Type 2 diabetes or at risk for Type 2 diabetes. Extra virgin olive oil is a nutrient-dense food with a low glycemic index. It is rich in mono-unsaturated fatty acids that are vital to improve cardio-metabolic risk factors in those at risk for Type 2 diabetes. Among all the oils, olive oils have a relatively high content of monounsaturated fatty acids. Diets rich in mono- and polyunsaturated fatty acids have shown favorable effects on cardiovascular health, glycemic control, insulin sensitivity, and lipid profile. All olive oils, (inclusive of extra virgin olive oil), have a relatively higher amount of monounsaturated fatty acids. While refined olive oils lack important antioxidants and anti-inflammatory properties, extra virgin olive oils specifically contains relatively higher levels of some minor phenolic compounds, along with more naturally-occurring minerals and vitamins found in olives that have favorable effects on cardio-metabolic health. Therefore, the inclusion of extra virgin olive oil in the diets of adults at risk for Type 2 diabetes is likely to confer better cardio-metabolic health benefits than a refined olive oil. Some oils improve, and some impair, endothelial function. Published studies have said both about olive oils, probably because the status and caliber of the olive oils was not always specified. We therefore propose to differentiate 'good' from 'bad' olive oils, and to show that extra virgin olive oils have decisively beneficial effects, while those effects are attenuated or lost as the oil is degraded. Specifically, proposed is a randomized crossover controlled trial to assess the impact of extra virgin olive oil, as compared with refined olive oil, on endothelial function in adults at risk for Type 2 diabetes.