Does chocolate reduce blood pressure? A meta-analysis

BackgroundDark chocolate and flavanol-rich cocoa products have attracted interest as an alternative treatment option for hypertension, a known risk factor for cardiovascular disease. Previous meta-analyses concluded that cocoa-rich foods may reduce blood pressure. Recently, several additional trials have been conducted with conflicting results. Our study summarises current evidence on the effect of flavanol-rich cocoa products on blood pressure in hypertensive and normotensive individuals.MethodsWe searched Medline, Cochrane and international trial registries between 1955 and 2009 for randomised controlled trials investigating the effect of cocoa as food or drink compared with placebo on systolic and diastolic blood pressure (SBP/DBP) for a minimum duration of 2 weeks. We conducted random effects meta-analysis of all studies fitting the inclusion criteria, as well as subgroup analysis by baseline blood pressure (hypertensive/normotensive). Meta-regression analysis explored the association between type of treatment, dosage, duration or baseline blood pressure and blood pressure outcome. Statistical significance was set at P ResultsFifteen trial arms of 13 assessed studies met the inclusion criteria. Pooled meta-analysis of all trials revealed a significant blood pressure-reducing effect of cocoa-chocolate compared with control (mean BP change +/- SE: SBP: -3.2 +/- 1.9 mmHg, P = 0.001; DBP: -2.0 +/- 1.3 mmHg, P = 0.003). However, subgroup meta-analysis was significant only for the hypertensive or prehypertensive subgroups (SBP: -5.0 +/- 3.0 mmHg; P = 0.0009; DBP: -2.7 +/- 2.2 mm Hg, P = 0.01), while BP was not significantly reduced in the normotensive subgroups (SBP: -1.6 +/- 2.3 mmHg, P = 0.17; DBP: -1.3 +/- 1.6 mmHg, P = 0.12). Nine trials used chocolate containing 50% to 70% cocoa compared with white chocolate or other cocoa-free controls, while six trials compared high- with low-flavanol cocoa products. Daily flavanol dosages ranged from 30 mg to 1000 mg in the active treatment groups, and interventions ran for 2 to 18 weeks. Meta-regression analysis found study design and type of control to be borderline significant but possibly indirect predictors for blood pressure outcome.ConclusionOur meta-analysis suggests that dark chocolate is superior to placebo in reducing systolic hypertension or diastolic prehypertension. Flavanol-rich chocolate did not significantly reduce mean blood pressure below 140 mmHg systolic or 80 mmHg diastolic.Karin Ried, Thomas Sullivan, Peter Fakler, Oliver R. Frank and Nigel P. Stock

Effect of garlic on blood pressure: A systematic review and meta-analysis

The electronic version of this article is the complete one and can be found online at the publisher's website.Background: Non-pharmacological treatment options for hypertension have the potential to reduce the risk of cardiovascular disease at a population level. Animal studies have suggested that garlic reduces blood pressure, but primary studies in humans and non-systematic reviews have reported mixed results. With interest in complementary medicine for hypertension increasing, it is timely to update a systematic review and meta-analysis from 1994 of studies investigating the effect of garlic preparations on blood pressure. Methods: We searched the Medline and Embase databases for studies published between 1955 and October 2007. Randomised controlled trials with true placebo groups, using garlic-only preparations, and reporting mean systolic and/or diastolic blood pressure (SBP/DBP) and standard deviations were included in the meta-analysis. We also conducted subgroup meta-analysis by baseline blood pressure (hypertensive/normotensive), for the first time. Meta-regression analysis was performed to test the associations between blood pressure outcomes and duration of treatment, dosage, and blood pressure at start of treatment. Results: Eleven of 25 studies included in the systematic review were suitable for meta-analysis. Meta-analysis of all studies showed a mean decrease of 4.6 ± 2.8 mm Hg for SBP in the garlic group compared to placebo (n = 10; p = 0.001), while the mean decrease in the hypertensive subgroup was 8.4 ± 2.8 mm Hg for SBP (n = 4; p < 0.001), and 7.3 ± 1.5 mm Hg for DBP (n = 3; p < 0.001). Regression analysis revealed a significant association between blood pressure at the start of the intervention and the level of blood pressure reduction (SBP: R = 0.057; p = 0.03; DBP: R = -0.315; p = 0.02). Conclusion: Our meta-analysis suggests that garlic preparations are superior to placebo in reducing blood pressure in individuals with hypertension.Karin Ried, Oliver R. Frank, Nigel P. Stocks, Peter Fakler and Thomas Sulliva

Commentary: Studying block in cloned N-methyl-D-aspartate (NMDA) receptors

The biophysics of block of NMDA receptor channels has been investigated extensively during the past 8 years. In the last few years, cloned NMDA receptor channels have become available. Here we have discussed advantages and disadvantages of studying block phenomena in cloned NMDA receptors. Some recent work on the pore block of the cloned NMDA receptor channels was critically reviewed and extended by data about the calcium block. Novel effects of kainate on cloned NMDA receptors and of NMDA on cloned AMPA receptors were reported and discussed with respect to recent work concerning possible occurrence of NMDA-AMPA hybrid channels

Short antisense oligonucleotide-mediated inhibition is strongly dependent on oligo length and concentration but almost independent of location of the target sequence

The inhibitory effect of short antisense oligodeoxynucleotides (aODNs) on cRNA expression in Xenopus oocytes was measured using an electrophysiological assay based on subunit-specific block of cloned alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate receptors. The effect of both phosphorothioate-modified (PS) and phosphodiester (PO) aODNs was strongly length dependent with a half-maximal inhibition calculated for an oligo length of 7.6 nucleotides (nt) and 9.9 nt, respectively. More than 95% inhibition was mediated by a PS aODN of 12 nt and by PO aODNs > or = 15 nt. At a given length PS and PO aODNs showed differential dependence of their inhibitory effect on the injected aODN concentration (half-maximal inhibition at 18 ng/microliter for a PO 12-mer and at 0.19 ng/microliter for a PS 12-mer) and differential saturation behavior. The inhibitory effect of aODNs, even as short as 8 nt for PS oligomers, was highly sequence specific, but almost independent of the position of the respective target site on the cRNA (for PS 8-mers, > or = 70% expression inhibition throughout the tested target sites from the translation initiation to the 3-untranslated region). Thus, short PS aODNs can be reliably used in order to specifically inhibit protein expression in experiments addressing physiological, molecular biological, and perhaps even therapeutical issues

A structural determinant of differential sensitivity of cloned inward rectifier K+ channels to intracellular spermine

Large subtype-specific differences in the sensitivity of cloned inward-rectifier K+ channels of the IRK1, BIR10 and ROMK1 subtype to being blocked by intracellular spermine (SPM) are described. It is shown, by site-directed mutagenesis, that the four orders of magnitude larger SPM sensitivity of BIR10 channels compared to ROMK1 channels may be explained by a difference in a single amino acid in the putative transmembrane segment TMII. This residue, a negatively charged glutamate in BIR10, is homologous to the residue in IRK1 and ROMK1 which has previously been shown to change gating properties and Mg2+ sensitivity. Differential block by physiological SPM concentrations is suggested as a major functional difference between subtypes of inward-rectifier K+ channels