Olive Oil

Scientific Evidence for Olive Oil in the Prevention of Cardiovascular Risk Factors and Coronary Heart Disease

Information compiled by Dr Mario Saliba from Eurosciences Communication in co-operation with the Institute of Arteriosclerosis Research at the University of Münster, Germany

Olive oil and Cardiovascular Risk Factors

Olive oil and hypertension

The relationship between dietary fats and blood pressure is not definitively answered. However, evidence suggests that the multiple components of the Mediterranean diet, i.e. low saturated fatty acids (SFAs), high monounsaturated fatty acids (MUFAs), and carbohydrate, fibre, and micronutrient content have favourable blood pressure effects, and therefore that this diet is desirable for health. Dietary MUFA may have a greater protective effect than initially realised.

Olive oil and diabetes

The traditional Mediterranean diet meets all the demands of an adequate diabetes diet. It contains a lot of vegetables and cereals. Carbohydrates are mainly taken up as fibre-rich carbohydrates. It has a low SFA content and is rich in MUFA, mainly from olive oil. The absolute fat content can be varied depending on individual needs. Clearly it is important for diabetic obese patients to lose weight as well as to adopt a healthier diet.

Olive oil and obesity

In Western countries we eat twice as much animal fat as is recommended. This can lead to obesity which is associated with a number of other disease risks. A diet rich in complex carbohydrates and fibre will protect against obesity. A Mediterranean diet will provide optimal energy intake and provides a means with which to treat or prevent obesity.

Olive oil and thrombogenic risk factor

Most studies suggest that for antithrombotic effects a low fat or a vegetable-fat diet is preferable to a high-fat diet, particularly a high fat diet high in SFAs. The Mediterranean diet meets these requirements and therefore can be recommended for the prevention of thrombosis.

Olive Oil and Coronary Heart Disease

Epidemiological Studies

The Seven Countries Study published in 1970 reported on the dietary intake, blood pressure and cholesterol levels of 13,000 men aged 40-59 years at entry living in Italy, Greece, the former Yugoslavia, the Netherlands, Finland, USA and Japan. CHD deaths were closely related to age, blood pressure and smoking. Saturated fat intake and serum cholesterol levels of the populations were significantly correlated at baseline, 5 and 10 year follow up.

Major differences in the proportions of SFAs and MUFA consumption existed between the Mediterranean countries, northern Europe and the US. Death rates within 15 years were low among the high olive oil consumers where SFA was low (i.e. a high MUFA:SFA ratio): namely, Greece, Italy and Yugoslavia. However, high MUFA intake in the US was apparently counteracted by their high SFA intake (i.e. low MUFA:SFA ratio) and here the CHD mortality was high. Evidence from the Greek island Crete suggested that besides the cholesterol lowering properties of oleic acid (largely from olive oil), other cardioprotective benefits were derived from nutrients and non-nutrients in the Mediterranean diet (e.g. antioxidative vitamins).

Some Mediterranean countries have retained their eating habits over the past 40 years and still show an advantage in terms of lower CHD mortality compared to western Europe and the US.

Intervention Studies

Many randomised prevention studies have firmly established the links between dietary SFA, serum cholesterol and CHD. Most of the studies involved decreasing SFA and increasing polyunsaturated fatty acids (PUFAs) and they had positive outcomes. None of the trial diets were particularly high in MUFAs and therefore the typical Mediterranean diet has not been tested for the primary prevention of CHD.

Diets similar to those of Mediterranean countries have been investigated in intervention trials and trials where compliance is highly controlled. These diets efficiently lower serum cholesterol and LDL cholesterol, without adversely affecting HDL cholesterol. Such reductions in cholesterol result in reduced morbidity and mortality. Recently it has been shown that intensive lipid-lowering with drugs in men with moderate hypercholesterolaemia and no history of cardiovascular events, reduces the incidence of heart attack and CHD morality, without increasing non-cardiovascular mortality.

Dietary Recommendations

Many national and international guidelines recommend preventive diets similar to the traditional Mediterranean diet. They suggest the following:

total fat should be reduced to 30% of energy
SFA intake be reduced to below 10%
PUFA intake to be no more than 10% of energy (7-10%)
MUFA intake should constitute 10-15% of energy
dietary cholesterol should be below 300mg/day
intake of complex carbohydrates and fibre should be increased

The Mediterranean diet has:

abundance of plant foods, bread, grain products, vegetables, legumes
fruit
low to moderate amounts of animal products
olive oil as principal source of fat/high MUFA content
low in SFA
rich in carbohydrate and fibre

With ingredients like this, these recommendations can be converted into a tasty and appetising diet.

Olive oil in secondary prevention of CHD

Agressive treatment of all coronary risk factors, including diet, is an important management approach in secondary prevention of CHD. There is much evidence that diets low in animal products and SFA are associated with low cholesterol levels and reduced CHD rates. Diets high in MUFAs (mainly from oleic acid) also provide this benefit, which is achieved through direct effects on risk factors such as hyperlipidaemia, high blood pressure and so forth, but also via directly protective effects like antioxidant activity.