Cocoa flavanol consumption linked to improvements in cardiometabolic biomarkers

To the tantalizing delight of chocolate lovers everywhere, a number of recent studies employing various methods have suggested that compounds in cocoa called flavanols could benefit cardiovascular health. Now a systematic review and meta-analysis of 19 randomized controlled trials (RCTs) of cocoa consumption reveals some further pieces of supporting evidence.

The meta-analysis in the Journal of Nutrition, an assessment of the combined evidence from all 19 RCTs, focused on whether consumption of flavanol-rich cocoa products was associated with improvements in specific circulating biomarkers of cardiometabolic health as compared to consuming placebos with negligible cocoa flavanol content. In all, 1,139 volunteers were involved in these trials.

"Our meta-analysis of RCTs characterizes how cocoa flavanols affect cardiometabolic biomarkers, providing guidance in designing large, definitive prevention trials against diabetes and cardiovascular disease in future work," said corresponding author Dr. Simin Liu, professor and director of the Center for Global Cardiometabolic Health at Brown University who worked with epidemiology graduate student and lead author Xiaochen Lin. "We found that cocoa flavanol intake may reduce dyslipidemia (elevated triglycerides), insulin resistance and systemic inflammation, which are all major subclinical risk factors for cardiometabolic diseases."

Liu noted some limitations in the trials. All studies were small and of short duration, not all of the biomarkers tracked in these studies changed for the better, and none of the studies were designed to test directly whether cocoa flavanol consumption leads to reduced cases of heart attacks or type 2 diabetes.

But taking into account some of these heterogeneities across studies, the team's meta-analysis summarizing data from 19 trials found potential beneficial effects of flavanol-rich cocoa on cardiometabolic health. There were small-to-modest but statistically significant improvements among those who ate flavanol-rich cocoa product vs. those who did not.

The greatest effects were seen among trial volunteers who ate between 200 and 600 milligrams of flavanols a day (based on their cocoa consumption). They saw significant declines in blood glucose and insulin, as well as another indicator of insulin resistance called HOMA-IR. They also saw an increase in HDL, or "good," cholesterol. Those consuming higher doses saw some of the insulin resistance benefits and a drop in triglycerides, but not a significant increase in HDL. Those with lower doses of flavanols only saw a significant HDL benefit.

In general, Lin said, where there were benefits they were evident for both women and men and didn't depend on what physical form the flavanol-rich cocoa product was consumed in --dark chocolate vs. a beverage, for example.

"The treatment groups of the trials included in our meta-analysis are primarily dark chocolate -- a few were using cocoa powder-based beverages," Lin said. "Therefore, the findings from the current study apparently shouldn't be generalized to different sorts of chocolate candies or white chocolates, of which the content of sugar/food additives could be substantially higher than that of the dark chocolate."

The authors therefore concluded, "Our study highlights the urgent need for large, long-term RCTs that improve our understanding of how the short-term benefits of cocoa flavanol intake on cardiometabolic biomarkers may be translated into clinical outcomes."

High Flavanol Consumption May Counteract Sitting-Induced Endothelial Dysfunction

In continuation of my update on Flavanol

Consuming high-flavanol foods and drinks may reduce some of the impact of prolonged sitting on the vascular system, according to a study published online Oct. 29 in the Journal of Physiology.

Alessio Daniele, from the University of Birmingham in the United Kingdom, and colleagues investigated whether intake of dietary flavanols prior to a two-hour sitting bout can preserve upper- and lower-limb endothelial function in high- and low-fit individuals. The analysis included 40 young, healthy men (20 high-fit; 20 low-fit) who completed a two-hour sitting trial after consuming either a high-flavanol (150 mg epicatechin) or low-flavanol (<6 mg epicatechin) cocoa intervention.

The researchers found that sitting significantly reduced flow-mediated dilation (FMD) in the superficial femoral artery and brachial artery. Sitting also increased diastolic blood pressure (BP) in both fitness groups. High-flavanol consumption prevented FMD declines in both arteries, with no effects on BP. There were significant decreases in shear rate and blood flow in both arteries in both fitness groups with sitting, with no effects of the flavanol intervention. Sitting was also associated with declines in tissue oxygenation (TOI), detectable within 10 minutes, and impaired TOI desaturation and speed of reperfusion during hyperemia two hours after sitting, with no effects of flavanols.

"Given how common sedentary lifestyles have become and the increased risk this can have to vascular health, using flavanol-rich food and drink, especially in combination with breaking up periods of inactivity by going for a short walk or standing up, could be a good way to enhance long-term health, no matter the individual's fitness level," coauthor Catarina Rendeiro, also from University of Birmingham, said in a statement.

Abstract/Full Text

https://en.wikipedia.org/wiki/Flavonols

High Flavanol Consumption May Counteract Sitting-Induced Endothelial Dysfunction - Drugs.com MedNews

Endothelial Function Improvement With Dietary (Cocoa) Flavanols in Patients With Coronary Artery Disease....

A new study by UCSF cardiologists and researchers lead by Dr. Yerem Yeghiazarians found that high concentrations of cocoa flavanols decrease blood pressure, improve the health of blood vessels and increase the number of circulating blood-vessel-forming cells in patients with heart disease. The findings indicate that foods rich in flavanols  such as cocoa products, tea, wine, and various fruits and vegetables have a cardio-protective benefit for heart disease patients.

Flavanols are phytonutrient compounds that are found naturally in apples, grapes, tea, cocoa and cherries, which account for the antioxidant effect provided by red wine and green tea. The study found a protective effect from a cocoa drink with 375 mg of flavanols, but according to researchers, a standard or recommended dosage has not yet been defined to achieve optimal health benefit.

The UCSF team has shown for the first time that one of the possible mechanisms of flavanol's benefit is an increase in the circulation of so-called angiogenic cells in the blood. These cells, also known as early endothelial progenitor cells, are critical for the repair process after vascular injury, and perform function and maintenance roles in the endothelium. Endothelium is the thin layer of cells that line the interior wall of blood vessels.

In the current study, the benefit seen from the two-fold increase in circulating angiogenic cells was similar to that achieved by therapy with statins and with lifestyle changes such as exercise and smoking cessation. The benefit demonstrated with cocoa flavanol therapy occurred in addition to the medical regimen already being taken by study participants.

"Our data support the concept that dietary flavanols at the levels provided -- in tandem with current medical therapy -- are safe, improve cardiovascular function, and increase circulating angiogenic cells, which have previously been shown to correlate positively with long-term cardiovascular outcomes" said Yeghiazarians.

Though long-term trials examining the effects of high-flavanol diets on cardiovascular health and function are warranted, but these early findings help us understand how these compounds impact the function of damaged blood vessels...

Ref : Yerem Yeghiazarians et.al., J. Am. Coll. Cardiol., July 13, 2010; 56: A20.