Does chocolate reduce blood pressure? A meta-analysis

Nondrug interventions for treatment of hypertension

The treatment of hypertension is no longer limited to the simple prescription of pharmaceuticals. For many patients, maximal medical therapy is insufficient to adequately treat refractory hypertension. In addition, some patients may prefer to explore therapies that do not involve drugs as an initial step. Utilizing our broadening understanding of the physiology of hypertension, new technology and interventions have been developed that allow for treatments that do not rely on medications. In addition, dietary supplements and modification, as well as herbal supplements, may be useful under the right circumstances. Lifestyle modification remains a necessary part of treatment for all patients with hypertension. This article will review the evidence behind some available nondrug interventions for the treatment of hypertension.

Chocolate consumption and cardiometabolic disorders: systematic review and meta-analysis

OBJECTIVE

To evaluate the association of chocolate consumption with the risk of developing cardiometabolic disorders.

DESIGN

Systematic review and meta-analysis of randomised controlled trials and observational studies.

DATA SOURCES

Medline, Embase, Cochrane Library, PubMed, CINAHL, IPA, Web of Science, Scopus, Pascal, reference lists of relevant studies to October 2010, and email contact with authors.

STUDY SELECTION

Randomised trials and cohort, case-control, and cross sectional studies carried out in human adults, in which the association between chocolate consumption and the risk of outcomes related to cardiometabolic disorders were reported.

DATA EXTRACTION

Data were extracted by two independent investigators, and a consensus was reached with the involvement of a third. The primary outcome was cardiometabolic disorders, including cardiovascular disease (coronary heart disease and stroke), diabetes, and metabolic syndrome. A meta-analysis assessed the risk of developing cardiometabolic disorders by comparing the highest and lowest level of chocolate consumption.

RESULTS

From 4576 references seven studies met the inclusion criteria (including 114,009 participants). None of the studies was a randomised trial, six were cohort studies, and one a cross sectional study. Large variation was observed between these seven studies for measurement of chocolate consumption, methods, and outcomes evaluated. Five of the seven studies reported a beneficial association between higher levels of chocolate consumption and the risk of cardiometabolic disorders. The highest levels of chocolate consumption were associated with a 37% reduction in cardiovascular disease (relative risk 0.63 (95% confidence interval 0.44 to 0.90)) and a 29% reduction in stroke compared with the lowest levels.

CONCLUSIONS

Based on observational evidence, levels of chocolate consumption seem to be associated with a substantial reduction in the risk of cardiometabolic disorders. Further experimental studies are required to confirm a potentially beneficial effect of chocolate consumption.

Dietary flavonoids: Role of (-)-epicatechin and related procyanidins in cell signaling

Plant polyphenols are among the most abundant phytochemicals present in human diets. Increasing evidence supports the health-promoting effects of certain polyphenols, including flavonoids. This review discusses current knowledge of the capacity of monomeric flavanols, i.e., (-)-epicatechin and (+)-catechin, and their derived procyanidins to modulate cell signaling and the associations of these actions with better health. Flavanols and procyanidins can regulate cell signaling through different mechanisms of action. Monomers and dimeric procyanidins can be transported inside cells and directly interact and modulate the activity of signaling proteins and/or prevent oxidation. Larger and nonabsorbable procyanidins can regulate cell signaling by interacting with cell membrane proteins and lipids, inducing changes in membrane biophysics, and by modulating oxidant production. All these actions would be limited by the bioavailability of flavanols at the target tissue. The protection from cardiac and vascular disease and from cancer that is associated with a high consumption of fruit and vegetables could be in part explained by the capacity of flavanols and related procyanidins to modulate proinflammatory and oncogenic signals.

Nuts, hypertension and endothelial function

BACKGROUND AND AIMS

High blood pressure (BP) is considered a major risk factor for cardiovascular disease. Among lifestyle factors, diet plays a key role in the prevention and control of high BP. Therefore, it is important to elucidate which dietary components can exert beneficial effects on BP through modulation of endothelial function (EF) or by other mechanisms. In this paper we review the role of nutrients, foods, particularly nuts, and dietary patterns on BP control.

DATA SYNTHESIS

Because nuts are low in sodium and contain significant amounts of mono- and polyunsaturated fatty acids, fiber, minerals such as magnesium, potassium and calcium, and antioxidants, they have been suggested as potentially protective foods against hypertension. Limited evidence from prospective studies and clinical trials suggests that nut consumption has a beneficial effect on both BP and EF. However, BP changes were a secondary outcome in nut feeding trials and no study used ambulatory BP monitoring as the standard for BP measurements.

CONCLUSIONS

Further clinical trials, ideally using ambulatory BP monitoring, are needed to establish the potential protective effect of nut consumption on hypertension and vascular reactivity.

Compliance, tolerability and safety of two antioxidant-rich diets: a randomised controlled trial in male smokers

It has been suggested that antioxidants attenuate oxidative stress and prevent oxidative stress-related diseases. Paradoxically, randomised controlled trials (RCT) using pharmacological doses of antioxidant supplements have demonstrated harmful effects in smokers. The aim of the present study was to test the compliance, tolerability and safety of two food-based antioxidant-rich diets in smokers. One of the diets provided antioxidants at levels similar to that used in RCT using supplements which previously have generated harmful effects. The present study followed a randomised, parallel-arm dietary intervention for 8 weeks (n102) in male smokers (age ≥ 45 years). Participants were randomised to either antioxidant-rich diet, kiwi fruit or control groups. The antioxidant-rich foods provided about 300 mmol antioxidants/week from a wide range of plant-based food items. The kiwi fruit group consumed three kiwi fruits/d. Compliance to both diets was good. Only mild, undesirable events were reported by a minority of the participants. The safety of both diets was demonstrated as no potentially harmful or pro-oxidative effects were observed. In the antioxidant-rich diet group, the mean intake of antioxidants increased from 30 mmol/d at baseline to 62 mmol/d during the intervention. In conclusion, we have demonstrated that male smokers can comply with two food-based antioxidant-rich diets. Furthermore, the present study is the first to demonstrate the tolerability and safety of dietary antioxidants at levels similar to dosages provided in RCT using supplements. Such diets may be useful in future studies investigating whether dietary antioxidants may reduce oxidative stress and related diseases.

Cocoa flavanols: effects on vascular nitric oxide and blood pressure

Diets rich in fruits and vegetables have been associated with benefits for human health. Those effects have been partially ascribed to their content in flavonoids, compounds that are present in many edible plants and its derived foods. In humans, a significant number of studies has been developed analyzing the effect of foods and beverages rich in flavonoids on the presence and progression of risk factors associated to cardiovascular diseases, including hypertension. Cocoa derived products, rich in flavanols, have been thoroughly studied and demonstrated to be efficient improving endothelial function and decreasing blood pressure in humans and animals. However, the final chemical species and the mechanism/s responsible for these effects have not been completely defined. In this paper we present data supporting the hypothesis that flavanols could define superoxide anion production and then, establish optimal nitric oxide levels and blood pressure.

Protective effect of lycopene on serum cholesterol and blood pressure: Meta-analyses of intervention trials

BACKGROUND

Cardiovascular disease is associated with oxidative stress, inflammatory processes, and vascular dysfunction. Lycopene, a carotenoid found in tomatoes, is an antioxidant with a protective effect on lipid peroxidation and anti-atherosclerotic capacity. This review summarises current evidence on the effect of lycopene on serum lipid concentrations and blood pressure.

METHODS

We searched the PubMed and Cochrane databases for intervention studies between 1955 and September 2010 investigating the effect of lycopene on blood lipids or blood pressure for a minimum duration of 2 weeks. We conducted meta-analyses using a random effect model of all studies fitting the inclusion criteria. Additionally, we conducted subgroup meta-analysis of serum lipid concentrations by lycopene dosage and subgroup meta-analysis by baseline blood pressure.

RESULTS

Twelve studies (13 trial arms) meeting the inclusion criteria investigated the effect of lycopene on serum lipids, and four studies examined its effect on blood pressure. Meta-analysis on serum lipids revealed a significant cholesterol-lowering effect of lycopene for total serum cholesterol (mean change±SE: -7.55±6.15mg/dl; p=0.02) and low-density-lipoprotein (LDL) cholesterol (mean change±SE: -10.35±5.64mg/dl, p=0.0003) in the subgroup of trials using lycopene dosages of ≥25mg daily, whereas subgroup meta-analysis of trials using lower lycopene dosages was not significant. Meta-analysis of the effect of lycopene on systolic blood pressure of all trials suggested a significant blood pressure reducing effect (mean systolic blood pressure change±SE: -5.60±5.26mm Hg, p=0.04).

CONCLUSIONS

Our meta-analysis suggests that lycopene taken in doses ≥25mg daily is effective in reducing LDL cholesterol by about 10% which is comparable to the effect of low doses of statins in patient with slightly elevated cholesterol levels. More research is needed to confirm suggested beneficial effects on total serum cholesterol and systolic blood pressure.