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Cold Pressed Extra Virgin of course....
Olive Oil Part 1...

Several studies have shown that 2-4 tablespoons of olive oil daily (as the main source of fat in the diet and consumed with plant food) can have beneficial effects on blood fats (less atherogenic chylomicron remnants, triglycerides, oxidised LDL cholesterol), blood glucose, clotting factors and blood levels of antioxidants. It also appears to influence body fat distribution (less belly fat) and may even aid weight loss.

Less LDL cholesterol and more HDL cholesterol

Diets with olive oil as the dominant fat source may help reduce visceral fat, blood glucose, blood clotting, triglycerides and oxidation of LDL cholesterol and ultimately heart disease deaths. Despite high intakes of salt, the relatively low rates of strokes in Cretan men in the 1960's may have been due to the protective effect of the high intake of olive oil. In contrast, the Japanese men in the study had very low fat intakes (10% energy intake), high intakes of salt and much higher rates of stroke. However, the evidence that low fat diets may increase the risk of stroke is equivocal (Gillman et al. JAMA 1997; 278: 2145-50).

A 1985 report by Mattson and Grundy (J Lipid Res 1985; 26: 194-202) which showed monounsaturated fats could lower plasma cholesterol as much as polyunsaturated fat stimulated a reconsideration of the potential role of monounsaturated fats. Other studies since have resulted in the general consensus that both polyunsaturated and monounsaturated fats reduce blood LDL cholesterol when they replace saturated fats in the diet, but the polyunsaturated fats have a larger impact (Gardner & Kraemer Arterioscler Throm Vasc Biol 1995; 15: 1917-27). The effects on HDL cholesterol were similar, although some studies have shown that omega-6 fat can lower and monounsaturated fats tend to raise HDL cholesterol (Mensink et al. Arterioscler Thromb 1992; 12: 911-9).

Less oxidised LDL cholesterol

Olive oil may have played an important role in the healthiness of the Mediterranean diet in the 1960's and its value may be due to components other than its monounsaturated fats. Extra virgin olive oils contain 30-40 different antioxidant phytochemicals. The common practice of pouring olive oil over food just before it is eaten means the antioxidants are well preserved. When olive oil is used for cooking, the wide variety of antioxidants also act synergistically to prevent the formation of carcinogenic hydroperoxidation products which can arise in some heated fats higher in polyunsaturated fats (e.g. canola, sunflower).

There is growing evidence suggesting oxidation of LDL plays an important part in atherosclerosis (Steinberg Circulation 1991; 84: 1420-25). The process of LDL oxidation may be enhanced by polyunsaturated fats from plants and fish.

Omega-9 fat in plasma (e.g. in LDL) and cell membranes are less susceptible to oxidation in animal and human models. The reverse was found for omega 6 fats. In bench top studies, plasma LDL and cell membranes enriched in monounsaturated fat clearly resist oxidation compared to polyunsaturated fat (Abbey et al. AJCN 1993; 57: 391-8; Reaven AJCN 1991; 54: 701-6; J Clin Invest 1993; 91: 668-76). If the oxidation theory of atherosclerosis is correct, this should lead to less atherosclerosis on a monounsaturated fat enriched diet. However, animal studies do not support this hypothesis and unfortunately oleic acid levels in lipoproteins are not related to dietary intake of oleic acid. In the 7 countries study, monounsaturated fat intake was inversely related to mortality from CHD, but it is difficult to conclude that monounsaturated fat itself is protective.

Although evidence is still lacking that a reduction in the oxidisability of LDL will translate into a reduction in coronary events, there is suggestion of benefit. For example, a higher intake of the antioxidant vitamin E that is carried in LDL, is associated with less deaths from CHD (Rimm et al. NEJM 1993; 328: 1450-56).

A study by Ramirez-Tortosa et al (J Nutr 1999; 2177-83) placed men with peripheral vascular disease on 2 tablespoons per day of either extra virgin olive oil (<1% acidity) or fine virgin olive oil (1-2% acidity) or pure olive oil (2-3% acidity) for 3 months. The extra virgin olive oil was found to be significantly better in preventing oxidation of LDL cholesterol and lowering triglyceride levels. Unfortunately there was no comparison between olive oils and other types of vegetable oils. Other recent work suggests that peanut and canola oils may have a similar positive effect to olive oil, but a comparison with the extra-virgin type is not clear. If olive oil is to be used in a healthy diet, the earliest and least chemically contaminated stage of processing (i.e. the first pressing - extra virgin) is likely to be the most beneficial.

Less post-meal chylomicron remnants and triglycerides

The link between blood fats and atherosclerosis has been chiefly attributed to elevated plasma LDL and low HDL concentrations. Fasting levels of these lipoproteins do not, however, sufficiently discriminate between patients with and without CHD. Moreover, conventional management of lipid disorders does not account for humans existing mostly in the postprandial (i.e. non-fasting) state.

The notion that post meal blood fats are atherogenic was encapsulated 20 years ago in the ‘Atherogenic Remnant Hypothesis’ in which Zilversmit (Circulation 1979; 60: 473-85) stated that the accumulation of chylomicrons and chylomicron remnants that occur after fatty meals are causally related to the development of atherosclerosis. This hypothesis is well supported by experimental, genetic and clinical studies which should be viewed not as alternative, but as supplementary to the proven LDL Hypothesis (Watts et al. Aust NZ J Med 1998; 28: 816-23).

It is now recognised that post meal triglyceride concentrations are an important factor in the development of CHD. The magnitude of the postprandial lipidemic response has been causally related to the presence and progression of CHD (Stampfer et al. JAMA 1996; 276: 882-8).

Post-meal fats last in the blood from 6-12 hours before being cleared by the liver where they are converted to VLDL, LDL and HDL. Chylomicron remnants are just as atherogenic as LDL cholesterol and can have a prothrombotic effect – they can therefore do considerable damage to blood vessels during the 6-12 hour period. Postprandial triglycerides are indirectly atherogenic by stimulating the formation of the highly atherogenic small, dense LDL's and by activating the clotting factor VII (Roche & Gibney, BrJNutr 1997; 77:1-13).

There is emerging evidence that certain dietary fats may be cleared faster from the blood stream after a fatty meal, thereby reducing the risk of atheroma formation and blood clots.

Abia et al (J Nutr 1999; 129: 2184-99) have demonstrated that postprandial triglycerides after an olive oil (extra virgin) rich meal are selectively cleared in humans. A study by Roche, Zampelas and Kafatos (AJCN 1998; 68: 552-60) compared postprandial triacylglycerol concentrations and clotting factor VII activity in 23 northern European men. These men were consuming either a Mediterranean diet high monounsaturated (from olive oil), and low in saturated fats (20% and 12% energy respectively) or a high saturated, low monounsaturated fat diet (17% and 12% energy respectively). Both diets were consumed for 8 weeks and provided 40% energy as fat and 7% energy as polyunsaturated fat (20g omega 6 and 1g omega 3 fatty acids).

Postprandial clotting factor activity was lower on the monounsaturated fat diet compared with the saturated fat diet. Postprandial triglycerides returned to near-fasting concentration much earlier on the monounsaturated diet compared with the saturated fat diet.

This study presents new insights into the biochemical basis of the beneficial effects associated with long-term dietary monounsaturated olive oil consumption, which may explain the lower rates of coronary mortality in the Mediterranean, especially in the 1960s.

Chylomicron remnants after eating fish omega-3 fats may also be selectively cleared (Bergeron & Havel, Curr Opin Lipidol 1997; 8: 43-52). Saturated fats and alcohol consumed with a high fat meal delays the clearance of post meal fats in the blood.

Less blood clots and reduced risk of heart attack

A study from the University of Copenhagen (Larson et al. AJCN 1999; 70: 976-82) has demonstrated in a intervention study that a high olive oil intake lowers blood coagulation more (by 18%) than sunflower and rapeseed oils. The researchers suggest that a diet high in olive oil may indeed prevent the acute pro-coagulant effects of fatty meals and thus prevent sudden heart disease. Their findings offer clear support for other work now available also supporting the benefits of olive oil.

A new study published in the International Journal of Epidemiology in April 2002
(http://ije.oupjournals.org/cgi/content/abstract/31/2/474) looked at the use of olive oil in Spain and risk of a first heart attack. This was a case-control study involving 171 patients who had suffered a heart attack and an equal number of control subjects without evidence of heart disease. Those consuming the highest amount of olive oil had a reduction in risk of heart attack of 82 percent. This group consumed an average of 52 grams (about 3-4 tablespoons) per day.The statistical analysis controlled for smoking, diabetes, high blood pressure and high cholesterol since those with heart attacks were more likely to have these conditions. So, even when these factors were taken into account, olive oil was still found to be protective.





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