With commentary by lead study author Angela Rivellese, M.D., professor of applied dietetic sciences at Federico II University in Naples.
Adding olive oil to a meal improves glucose response in those with type 1 diabetes, researchers in Italy have found.
“Our study shows for the first time that the type of fat significantly influences post-prandial glycemic response in patients with type 1 diabetes,” said lead author Angela Rivellese, M.D., professor of applied dietetic sciences at Federico II University in Naples.
In short, extra virgin olive oil (EVOO) is better than butter. Study subjects who consumed meals with 37 grams of EVOO (2.5 tablespoons) showed an approximate 50% reduction in early, after-meal blood glucose response compared with those who consumed meals with either 43 grams of butter (2.9 tablespoons) or meals deemed low-fat (half-a-tablespoon of EVOO). The EVOO meals were also associated with a significant delay in the time it took for blood glucose to peak compared with the butter and low-fat meals.
The EVOO benefit was seen only in meals with a high glycemic index (HGI); it did not apply to meals with a low glycemic index (LGI). HGI foods cause a rapid rise in after-meal blood glucose levels, while LGI foods result in a slower and steadier release of glucose, which leads to healthier blood glucose readings.
The study, which suggests that carbohydrate-counting alone may not result in optimal glucose control, has important clinical implications for those with type 1 diabetes, the authors wrote, because it demonstrates that the combination of carbohydrates and type of fat should be considered in the timing and dosing of mealtime insulin.
“People living with type 1 diabetes routinely monitor their dietary intake of carbohydrates and often limit high glycemic index foods in order to manage blood glucose levels,” explained DiabeticLifestyle Medical Advisory Board Member Susan Weiner, RDN, CDE, American Association of Diabetes Educators 2015 Educator of the Year. “In addition to its nutritional benefits, EVOO may also improve blood glucose levels in some individuals with type 1 diabetes and therefore be beneficial as part of a healthy diet,” Weiner said, adding, however, that “people with type 1 diabetes should not assume that consuming excessive amounts of extra virgin olive oil will offset eating a diet rich in carbohydrates, and it may also not affect people with type 1 diabetes already consuming a low glycemic diet.”
Meanwhile, evidence is accumulating that EVOO may also play a role in improving after-meal blood glucose levels in healthy people and even in preventing type II diabetes. A study in Spain found that among adults facing a high risk of heart disease (a condition known to be a risk factor associated with type II diabetes), those whose diets were supplemented with EVOO were significantly less likely to develop type II diabetes than those whose diets were not.
And a 2015 study in Italy found that adults who consumed a Mediterranean diet-type meal supplemented with EVOO had significantly better post-prandial glycemic profiles than adults who consumed a similar meal supplemented with corn oil. The lead investigator of that study, Francesco Violi, M.D. professor of internal medicine at Sapienza University in Rome, said, “The present study of patients with type 1 diabetes confirms my own, showing that extra virgin olive oil possesses an antidiabetic effect by lowering post-prandial glycaemia.”
The Mediterranean Diet, which consists mainly of vegetables, fruits, beans, olive oil, whole grains and fish, and little dairy or red meat, has been associated over the years with a variety of health benefits including lower risks of heart disease, high blood pressure and stroke.
Some have speculated that many of the diet’s benefits are due to EVOO, and in particular to the oil’s high content of monounsaturated fat, said to be its main characteristic. “In our study,” Rivellese said of her trial in patients with type 1 diabetes, “monounsaturated fatty acids were three times higher in meals with EVOO than in those with butter.”