Compared to other kinds of fat, extra virgin olive oil may have healthier effects on levels of blood sugar and bad cholesterol after meals, according to an Italian study.
That may explain why a traditional Mediterranean diet rich in olive oil is linked to lower risk of cardiovascular disease, researchers say.
"Lowering (post-meal) blood glucose and cholesterol may be useful to reduce the negative effects of glucose and cholesterol on the cardiovascular system," lead study author Francesco Violi, a researcher at Sapienza University in Rome, said by email.
Violi and his colleagues tested the effect of adding extra virgin olive oil (EVOO) to a Mediterranean diet based on fruits, vegetables, grains and fish, with only limited consumption of dairy or red meat.
On two separate occasions, researchers gave 25 healthy people a typical Mediterranean lunch. For one meal, they added 10 grams (about 2 teaspoons) of extra virgin olive oil, and for the other, they added 10 g of corn oil.
Blood tests done before and two hours after the meals found that blood sugar rose after eating in all the participants, which is normal. But blood sugar rose much less after a meal with olive oil compared to one with corn oil.
That's in line with previous research linking EVOO to elevated levels of insulin, a hormone that helps convert glucose into energy, Violi said.
It's unclear, though, why the blood tests after meals with olive oil also showed lower levels of low-density lipoprotein (LDL), the bad kind of cholesterol that builds up in blood vessels and can lead to atherosclerosis, blood clots and heart attacks.
"Lowering (post-meal) blood glucose and cholesterol may be useful to reduce the negative effects of glucose and cholesterol on the cardiovascular system," Violi said.
Worldwide, more people die of cardiovascular diseases than any other cause. These conditions killed an estimated 17.5 million people in 2012, most often from heart disease or stroke, according to the World Health Organization (WHO).
Violi's team also found that after meals with corn oil, people had significantly higher levels of two kinds of LDL than they did after meals supplemented with extra virgin olive oil.
The study is quite small, and didn't explore whether adding corn oil to meals might be better than including no oil at all, the researchers acknowledge in the journal Nutrition and Diabetes.
Even so, they argue, theirs is among the first studies to link a Mediterranean diet containing extra virgin olive oil to lower blood sugar and LDL cholesterol after meals.
People who want to get any potential health benefits from extra virgin olive oil shouldn't take this experiment as permission to pour it on top of every meal, noted Arrigo Cicero, a scientist at Alma Mater Studiorum University of Bologna who wasn't involved in the study.
"Use extra virgin olive oil instead of other fats," Cicero said by email. "The assumption is it has to be included as a source of energy in the context of a balanced diet."
