THE EFFECT OF DARK AND WHITE CHOCOLATE ON BLOOD PRESSURE AND RENAL PERFUSION AS ASSESSED WITH DOPPLER ULTRASOUND IN HEALTHY VOLUNTEERS

Abstract

Objective: Dark chocolate (DC) is rich in calories but also in cocoa, a substance with anti-oxidative and antihypertensive properties. Acute intake of DC vasodilates coronary arteries, but the effect on blood pressure and renal hemodynamics is poorly understood. The aim of this randomized, placebo controlled study was to investigate whether DC induces changes in blood pressure and renal perfusion as assessed with Doppler ultrasound, both at rest and during sympathetic stimulation, as compared to cocoa-free white chocolate (WC). Design and method: Seventeen healthy volunteers aged 42±14 years (47% women) were randomized to eat 1g/kg of DC (70% cocoa) or 1g/kg of WC. The renal resistive index (RRI), a proxy of intra-renal vascular resistance, was measured just before and two hours after chocolate consumption. Blood pressure (BP) and heart rate were measured with a Finapress device. At each time point, a 3-minute handgrip test was performed as sympathetic stimulus; during the handgrip, supplementary RRI values were measured. Two weeks later, the same exams were repeated with the other type of chocolate. Results: DC intake decreased RRI from 0.62±0.04 to 0.60±0.04 (p=0.039), whereas RRI did not change after the intake of WC (before: 0.62±0.05, after: 0.62±0.04, p=0.47), see Figure. DC had no effect on BP in persons consuming >50g/chocolate/week, whereas SBP increased from 115±17 to 122±15 mmHg (p=0.02) in non regular chocolate eaters. Handgrip exercise also lowered the RRI from 0.62 to 0.57 (p=0.001) and flattened the Doppler curves, while increasing SBP (from 115±15 to 139±16mmHg, p=0.001). In women, the effect on RRI was attenuated by the ingestion of DC. Conclusions: The ingestion of DC lead to an acute reduction in RRI, suggesting intra-renal vasodilatation, whereas WC had no effect. BP only increased in non-regular DC eaters, suggesting that regular DC eaters got accustomed to the BP-modifying effects of DC. Handgrip exercise led, surprisingly, also to reductions in RRI, especially in young participants. Whether this is a sign of or sympathetically induced intra-renal vasodilatation or vascular reactivity needs further study.