The Mediterranean Diet: Health Benefits Of Olive Oil
Remarkably, there is a clinical link between onions, olive oil and blood pressure
Like garlic, onions may contribute more than mere taste to the Mediterranean diet. A group of researchers have found that onions may help lower blood pressure, and make platelets less sticky and hence less apt to clog up blood vessels.
Researchers gave a group of volunteers mashed-up onions and olive oil capsules, and gave a second group placebo, or dummy, capsules. The researchers found that after about 5 hours those getting the onion and olive oil mix had lower blood pressure. They also noted the blood was not as thick (lower viscosity) and that platelet stickiness was reduced. They then switched which group got the onion and olive oil pills and which group got the placebo pills, and the results again suggested the onion and olive oil pills were beneficial.
While this experiment needs to be repeated and the contribution of olive oil alone in lowering blood pressure must be sorted out, it is intriguing to think that onions, a common and important element of Mediterranean cuisine has its own health contribution to make.
There is even a significant link between olive oil and diabetes! The fundamental defect in adult onset diabetes is a diminished sensitivity to the effects of insulin, resulting in higher levels of glucose, or sugar, in the blood. As the body becomes more resistant to insulin, it pours out more and more insulin to keep glucose under control.
Another important but less well known condition associated with diabetes is a defect in the blood vessels that results in less blood flow. This impairment in the "endothelium" of the blood vessels also puts diabetics at a higher risk of heart disease.
In a recent study researchers assessed the effects of switching diabetics from a diet rich in polyunsaturated fats such as corn oil, to a diet rich in olive oil. Olive oil is composed mostly of oleic acid, a monounsaturated fat.
Results of this study showed that the olive oil based diet improved insulin sensitivity and glucose transport as well as flow through blood vessels.
The authors conclude that changing from a polyunsaturated to monounsaturated fat diet in adult onset diabetes reduces insulin resistance and improves "endothelial function" of the blood vessel. This suggests yet another explanation for the benefits of the Mediterranean diet.
It wasn't long ago that we were told to replace saturated fats with the polyunsaturated fats that came from seed oils, and so Americans stocked their pantries with safflower oil, sunflower oil and especially corn oil. But recently there has been growing concern about this recommendation for a couple of reasons.
First, these highly processed, polyunsaturated seed oils oxidize very easily and it is now becoming apparent that many diseases are promoted by oxidation. Furthermore corn oil, sunflower oil and other seed oils are loaded with a type of polyunsaturated fat, (Omega 6, linoleic acid) that is used to make hormone like substances called "prostaglandins" that promotes excessive inflammation.
Olive oil is not a seed oil and has only small amounts of polyunsaturated fat. It is mostly a monounsaturated fat called oleic acid. Extra virgin olive oil is pure and unrefined.
Researchers compared the effects of olive oil and sunflower oil in 11 men who acquired diabetes as they got older (type 2 diabetics). They found these diabetic men did better with olive oil. Subjects consuming olive oil instead of sunflower oil not only had lower glucose and insulin levels, they had better cholesterol and triglyceride levels too.
Study subjects were 11 type 2 diabetics who were changed from their usual linoleic acid-rich diets to oleic acid-rich diets for two months. There was a significant correlation between the adipocyte membrane oleic acid : linoleic acid ratio and insulin mediated glucose tranport. Endothelium-dependent flow mediated vasodilatation was also positively related to the ratio of oleic acid to linoleic acid in the membranes of adipocytes.
The authors conclude that, in type 2 diabetes, a Mediterranean diet appears superior to a diet rich in polyunsaturated fats from seed oils and may reduce the risk of atherosclerosis.
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