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Scientific Evidence for Olive Oil and its Effects on Lipid Metabolism

Author: Eurosciences Communication in co-operation with the Institute of Arteriosclerosis Research at the University of Münster, Germany

Coronary heart disease (CHD) is associated with a number of ‘risk factors' e.g., smoking, high blood pressure and hyperlipidaemia. Of these risk factors, cholesterol is particularly important.

Evidence from many sources (genetic, experimental, epidemiological and clinical trial data) consistently shows a strong, independent relationship between plasma cholesterol and CHD.

Lowering cholesterol levels produces a statistically significant reduction in the incidence of heart attacks. Typically, a 1% reduction in cholesterol produces a 2-3% reduction in CHD risk.

It is now understood that there are two types of cholesterol - low-density lipoprotein (LDL) and high-density lipoprotein (HDL) - the so-called ‘bad' and ‘good' cholesterol respectively. High levels of HDL cholesterol reduce the risk of CHD, whereas increased levels of LDL cholesterol increase CHD risk. In addition, high levels of another sort of fat - triglycerides, particularly in the presence of low levels of HDL and elevated levels of LDL, also confer high risk.

Because of the major contribution of dietary factors to serum lipids and lipoproteins, diet is a cornerstone in the prevention and treatment of CHD. In the Western diet the three saturated fatty acids (SFAs), lauric (e.g. palm kernel oil, coconut) myristic (e.g. butter, coconut oil) and palmitic (e.g. animal fat) acids comprise 60-70% of the total SFA content, and are responsible for the cholesterol-raising effect of saturated fat. Stearic acid, found in cocoa butter, is essentially neutral. A common strategy is to reduce SFA in the diet and replace it with polyunsaturated fatty acids (PUFAs), monounsaturated fatty acids (MUFAs) or complex carbohydrates in order to retain a suitable energy balance.

The major dietary PUFA is linoleic acid, which is predominant in vegetable oils (e.g. sunflower oil); when substituted for SFAs, this markedly reduces total cholesterol. Other PUFAs include alpha-linolenic acid (e.g., soybean and rapeseed oils) and eicosapentaenoic and docosahexaenoic acids - contained in marine fats and oils (e.g. herring and mackerel), which effectively lower triglycerides, having only minor effects on HDL and LDL cholesterol.

The major MUFA in the diet is oleic acid, which is the predominant fat in olive oil. Olive oil is a major component in the Mediterranean diet, to which it contributes more than 15% of energy. Studies have shown that blood cholesterol levels and the incidence of CHD are much lower in the Mediterranean than other countries.

Both MUFAs and PUFAs significantly reduce LDL levels when substituted for SFAs. A high MUFA intake will not alter HDL cholesterol levels significantly. Results of feeding trials involving LDL cholesterol in subjects fed high-MUFA diets have shown that it is quite resistant to oxidation. (Oxidation causes free radical production, which is detrimental to cells). Because of the high consumption of MUFAs among the Mediterranean population over the centuries, MUFAs are generally regarded as safe.

In accordance with recent European and American dietary guidelines, both fat reduction and the modification of what type of fat you eat are important. Consumption of olive oil increases MUFA intake without significant elevation of SFA and ensures an appropriate intake of the essential PUFAs. Therefore it can make a valuable contribution to a healthy diet, reducing the risk of CHD.

Source: http://europa.eu.int/comm/agriculture/prom/olive/medinfo/index.htm