1. Hepatic Origin of Cholesteryl Oleate in Coronary Artery Atherosclerosis In African Green Monkeys, Enrichment By Dietary Monounsaturated Fat, Journal of Clinical Investigation, 1997
"[We observed in monkeys] that the amount of coronary artery atherosclerosis was similar in the monounsaturated and saturated fat groups, in spite of the significantly improved LDL cholesterol concentration and LDL/HDL cholesterol ratio in the former."2. Dietary Monounsaturated Fatty Acids Promote Aortic Atherosclerosis In LDL Receptor–Null, Human ApoB100–Overexpressing Transgenic Mice, Arteriosclerosis, Thrombosis, and Vascular Biology, 1998
Mice were fed one of 6 diets with different fatty acid content: saturated, monounsaturated (cis and trans), polyunsaturated (n-3 and n-6), and a control diet.
"The reduction in aortic atherosclerosis was not found when either cis or trans monounsaturated fatty acids were fed. Rather, just as much atherosclerosis was seen when cis monounsaturated fat diets were fed as when saturated fat was fed, and significantly more atherosclerosis was seen when the trans monounsaturated fatty acids were fed."3. Effect Of Fat And Carbohydrate Consumption On Endothelial Function, Lancet, December, 1999
This is an important outcome when one considers that monounsaturated fats, often in the form of olive oil, are widely promoted as being healthful and effective for protection against heart disease.
"Consumption of a meal high in monounsaturated fat was associated with acute impairment of endothelial function when compared with a [low-fat] carbohydrate-rich meal."4. The Postprandial Effect Of Components Of The Mediterranean Diet On Endothelial Function, Journal of the American College of Cardiology, November 2000
"Contrary to part of our hypothesis, our study found that omega-9 (oleic acid)-rich olive oil impairs endothelial function postprandially.
The mechanism appears to be oxidative stress because the decrease in FMD was reduced (71%) by the concomitant administration of vitamins C and E. Balsamic vinegar (red wine product) and salad reduced the postprandial impairment in endothelial function to a similar extent (65%).
In a clinical study, olive oil was shown to activate coagulation factor VII to the same extent as does butter (44). Thus, olive oil does not have a clearly beneficial effect on vascular function."
The major unsaturated fatty acids in olive oil are oleic acid (18:1n-9) and linoleic acid (18:2n-6) (42). A high-oleic and linoleic acid meal has recently been shown to impair FMD in comparison with a low-fat meal (28). (That's the study above by Ong et al.)
In terms of their effects on postprandial endothelial function, the beneficial components of the Mediterranean and Lyon Diet Heart Study diets appear to be the antioxidant-rich foods—vegetables, fruits ... not olive oil. Dietary fruits, vegetables, and their products appear to provide some protection against the direct impairment in endothelial function produced by high-fat foods, including olive oil."
Clearly, olive oil is not the heart-healthy food it's made out to be. It truly is a feat of marketing that a food which has been shown over and over to impair artery function exists in peoples' minds as an elixir. The Mediterranean diet, with its generous portions of fruits, vegetables, and whole grains, improves health not because of olive oil, but in spite of it.