09.06.07
Indication: Blood pressure
Source: JAMA, July 4, 2007;298(1):49-60.
Research: Investigators in this randomized, double-blind, placebo-controlled study set out to determine the effects of low doses of polyphenol-rich dark chocolate on blood pressure (BP). The study involved 44 adults aged 56 through 73 years (24 women, 20 men) with untreated upper-range pre-hypertension or stage 1 hypertension without concomitant risk factors. Participants were randomly assigned to receive either 6.3 grams (30 kcal) per day of dark chocolate containing 30 mg of polyphenols or matching polyphenol-free white chocolate, with a goal of determining the change in BP after 18 weeks. Secondary outcome measures included changes in plasma markers of vasodilative nitric oxide (S-nitrosoglutathione) and oxidative stress (8-isoprostane), and bioavailability of cocoa polyphenols.
Results: From baseline to 18 weeks, dark chocolate intake reduced mean systolic and diastolic BP by nearly 3 points and 2 points, respectively. Hypertension prevalence declined from 86% to 68%. The BP decrease was accompanied by a sustained increase of S-nitrosoglutathione by 0.23 (0.12) nmol/L, and a dark chocolate dose resulted in the appearance of cocoa phenols in plasma. White chocolate intake caused no changes in BP or plasma biomarkers. Researchers believe results in this relatively small sample of otherwise healthy individuals with above-optimal BP indicate that inclusion of small amounts of polyphenol-rich dark chocolate as part of a usual diet efficiently reduces BP and improves the formation of vasodilative nitric oxide.