I am frequently asked by clients, ‘What about olive oil? Shouldn’t I include it in my diet? Isn’t it heart-healthy?’ Recently many have been asking me the same questions about coconut oil, thanks to a slew of websites and popular books touting its (alleged) benefits. I will keep the science to a minimum here so you don’t all drop off to sleep, because this is an incredibly important subject.
What’s wrong with oils – any kind – is that they impair endothelial function. What’s endothelial function? It’s the ability of the thin layer of cells that line your blood vessels, to regulate the flow of blood through those vessels. A well-functioning endothelium keeps your blood vessels reasonably dilated, which in turn lowers your blood pressure and ‘smoothes’ the flow of blood. Endothelial dysfunction results in constricted arteries, raised blood pressure and turbid blood flow which in turn increase the risk of microscopic injuries to the blood vessels. These injuries are ‘patched up’ with cholesterol, like you would patch up a damaged plasterboard wall with Spakfilla. If the injuries are infrequent, the cholesterol ‘patch’ is soon reabsorbed and the artery wall is repaired with normal, healthy endothelial cells. If there are repeated injuries, the cholesterol patches aren’t reabsorbed, but instead start to form an atherosclerotic plaque, which narrows the lumen of the blood vessel (the hole through which the blood flows), eventually causing symptoms such as angina and erectile dysfunction, and increasing the risk of stroke and heart attack.
When you ingest extracted oils and fats, you impair the function of your endothelial cells for several hours (the duration of effect varies with the type of oil) and during this time period, the growth of atherosclerotic plaques accelerates dramatically. On the other hand, nuts do not impair endothelial function in spite of their high fat content, because they contain arginine, which endothelial cells use to make nitric oxide, a chemical that dilates blood vessels, prevents atherosclerotic plaque from forming on the vessel walls, and keeps blood flow smooth and even by preventing platelets from sticking together.
The benefits of the so-called Mediterranean diet are due to the high consumption of antioxidant-rich fruits and vegetables, and are impaired by the addition of oil. (See this study.)
The bottom line: extracting an oil from the nutritional matrix that it is packaged in by nature is asking for trouble. If you want to minimise your risk of cardiovascular disease, enjoy plant foods that are naturally high in fats, such as avocado, nuts and seeds, in moderation, but leave the extracted oils out of your diet.
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