Mediterranean diet has got a favourable effect on life expectancy. One of the crucial components of the diet are onions. In an open and a randomized, placebo-controlled, double-blind, cross-over phase-I study a spontaneous pharmacological effect 5 h after administration of an onion-olive-oil maceration capsule formulation on arterial blood pressure could be demonstrated in apparently healthy subjects. In addition to a decrease in arterial blood pressure, a significant reduction in plasma viscosity and haematocrit were observed. These results are indicating a vasodilative effect of the onion-olive-oil-maceration product. The stickiness of the platelets was reduced. The effects were stronger in subjects with reduced blood fluidity compared to those subjects with normal rheological parameters.

Twenty-four patients with arterial hypertension (WHO class I) received either 4 capsules of an onion-olive oil maceration product, containing essential ingredients of the Mediterranean diet, or placebo daily over a period of one week. In order to investigate the acute effect on arterial blood pressure, measurements were performed before and 5 h after the administration of the first dose of 4 capsules verum or placebo, respectively. For the evaluation of the long term effect further blood pressure measurements were performed after one week's treatment with a daily dose of 4 capsules. After a wash-out phase of 2 weeks followed by a crossover, the second study phase, which was identical in design, was carried out. In addition patients were instructed to measure their blood pressure 4 times daily at home for the whole study period. Haemorheological parameters (platelet aggregation, erythrocyte aggregation, plasma viscosity and haematocrit) were also determined at the measuring points mentioned above. The onion-olive oil maceration product led to a significant decrease in systolic blood pressure. There was also a trend towards a decrease in diastolic blood pressure. The improved blood fluidity observed resulted from a decrease in haematocrit. All effects could be shown immediately and after one week's administration.

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