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Dark chocolate lowers blood pressure
Flavonols are a particular subclass of polyphenols that are found in cocoa products. They have previously been shown to lower blood pressure and improve endothelial function. However, this involved consumption of high doses of chocolate and follow-up was limited to 2 weeks only. Taubert et al therefore set out to determine the effect of low doses of polyphenol-rich dark chocolate on blood pressure (BP).
Forty-four adults aged between 56 and 73 years were randomised to receive either 6.3 g (30 kcal) a day of dark chocolate containing 30 mg of polyphenols or a matching polyphenol-free white chocolate. All had untreated upper-range prehypertension or stage 1 hypertension, without concomitant risk factors. The primary outcome measure was the noted change in BP at 18 weeks. Secondary outcome measures were changes in plasma markers of vasodilative nitric oxide (S-nitrosoglutathione) and oxidative stress (8-isoprostane), and bioavailability of cocoa phenols.
From baseline to 18 weeks, dark chocolate intake reduced mean (SD) systolic BP by 2.9 (1.6) mm Hg (p<0.001) and diastolic BP by 1.9 (1.0) mm Hg (p<0.001), but no changes were noted in body weight, plasma levels of lipids, glucose and 8-isoprostane. Hypertension prevalence declined from 86% to 68% and the decrease in BP noted was accompanied by a sustained increase of mean (SD) S-nitrosoglutathione of 0.23 (0.12) nmol/l (p<0.001). Phenols were also noted in the plasma after a dark chocolate dose. White chocolate caused no changes in BP or plasma biomarkers.
Although conducted on a small sample, this study showed that dark chocolate intake was associated with a reduction in BP and improved formation of nitric oxide. However, it should be remembered that excessive intake of any form of chocolate may lead to weight gain and an increase in saturated fat levels that may negate the potential benefits shown here.