Olive oil has also been shown to have a beneficial effect on blood lipids but the new study, reported in the October issue of the American Journal of Clinical Nutrition (vol 80, no 4, 1012-1018), suggests that it may act in a number of ways to protect people from heart disease.
There is already considerable evidence to indicate that the Mediterranean diet reduces cardiovascular mortality but the new study looks at one of the major risk factors of heart disease.
About two thirds of strokes and half the incidence of heart disease are attributable to raised blood pressure, according to the World Health Organisation. Worldwide, high blood pressure is estimated to cause 7.1 million deaths, about 13 per cent of the total and about 4.4 per cent of the total chronic disease burden.
The food industry is coming under increasing pressure to tackle the rising burden of heart disease, using heart healthy ingredients to target at-risk consumers. Food and drinks for heart health were worth £100.7 million during 2002 in the UK alone, according to Datamonitor statistics that predict this figure will rise to £145.1 million by 2007.
The researchers from the University of Athens Medical School, Harvard School of Public Health and Sotiria Hospital in Athens recorded arterial blood pressure and other variables like sociodemographic, dietary and physical activity, among participants in the Greek arm of the European Prospective Investigation into Cancer and Nutrition (EPIC) study.
Of these participants, 20 343 had never received a diagnosis of hypertension. The analysis was based on a score that reflects adherence to the Mediterranean diet and, alternatively, the individual components and olive oil.
The Mediterranean diet score was significantly inversely associated with both systolic and diastolic blood pressure. Intakes of olive oil, vegetables, and fruit were significantly inversely associated with both systolic and diastolic blood pressure, whereas cereals, meat and meat products, and alcohol intake were positively associated with arterial blood pressure.
Mutual adjustment between olive oil and vegetables, which are frequently consumed together, indicated that olive oil has the dominant beneficial effect on arterial blood pressure in this population, concluded the authors.
"Olive oil intake is inversely associated with both systolic and diastolic blood pressure," Professor Dimitrios Trichopoulos, author and consulting epidemiologist at the University of Athens, told NutraIngredients.com. "It was not a striking difference but it was statistically significant."
However he added that the mechanism for this action is not yet well understood. "The main component of olive oil is monounsaturated fat but it also has hundreds of microcomponents."
A recent study at the Second University of Naples, Italy, demonstrated that a Mediterranean-style diet had beneficial effects on people with the metabolic syndrome - decreasing blood pressure as well as body weight, levels of glucose, insulin, total cholesterol, and triglycerides and causing a significant increase in levels of high-density lipoprotein cholesterol.
The Greek researchers will next investigate whether the Mediterranean diet has beneficial effects on people who already have coronary heart disease.