Beneficial effects of dark chocolate on exercise capacity in sedentary subjects: underlying mechanisms. A double blind, randomized, placebo controlled trial

Abstract

In heart failure patients the consumption of (-)-epicatechin ((-)-Epi)-rich cocoa can restore skeletal muscle (SkM) mitochondrial structure and decrease biomarkers of oxidative stress. However, nothing is known about its effects on exercise capacity and underlying mechanisms in normal, sedentary subjects. Twenty normal, sedentary subjects (∼50 years old) were randomized to placebo or dark chocolate (DC) groups and consumed 20 g of the products for 3 months. Subjects underwent before and after treatment, bicycle ergometry to assess VO2 max and work, SkM biopsy to assess changes in mitochondrial density, function and oxidative stress and blood sampling to assess metabolic endpoints. Seventeen subjects completed the trial. In the DC group (n=9), VO2 max increased (17% increase, p=0.056) as well as maximum work (watts) achieved (p=0.026) with no changes with placebo (n=8). The DC group evidenced increases in HDL levels (p=0.005) and decreased triglycerides (p=0.07). With DC, SkM evidenced significant increases in protein levels for LKB1, AMPK and PGC1α and in their active forms (phosphorylated AMPK and LKB1) as well as in citrate synthase activity while no changes were observed in mitochondrial density. With DC, significant increases in SkM reduced glutathione levels and decreases in protein carbonylation were observed. Improvements in maximum work achieved and VO2 max may be due to DC activation of upstream control systems and enhancement of SkM mitochondria efficiency. Larger clinical studies are warranted to confirm these observations.

A Systematic Review and Meta-Analysis of the Effects of Flavanol-Containing Tea, Cocoa and Apple Products on Body Composition and Blood Lipids: Exploring the Factors Responsible for Variability in Their Efficacy

“…The products were administered in different forms, mostly as green tea extracts/capsules or cocoa drinks and at different doses and intervention periods. Some of these studies further support the reduction of total- and LDL-cholesterol by green tea or cocoa flavanols or the increase of HDL by dark chocolate or cocoa [111,169,170,171]. Others show no significant effects on these variables [175].…”

“…Since the completion of this meta-analysis, additional RCTs investigating the effects of tea or cocoa products containing flavanols on lipid and anthropometric variables have been added to the existing literature [111,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183]. The heterogeneity of these trials remains high with population samples including mixed sexes and ages, obese, overweight, healthy, hyperlipidemic and/or diabetic subjects, etc.…”

Fruit-Derived Polyphenol Supplementation for Athlete Recovery and Performance

“…This was achieved both via reduced reactive oxygen species generation as well as increased endogenous antioxidant enzyme gene expression. Dark chocolate supplementation for 3 months has also been shown to enhance superoxide dismutase and catalase expression in muscle of patients with heart failure and type 2 diabetes [ 48 ], and more recently has been shown to reduce carbonylation of proteins within skeletal muscle of healthy adults [ 126 ]. In contrast, McLeay et al [ 117 ] only commenced blueberry supplementation 10 h prior to intensive exercise and hence increased endogenous antioxidant capacity is an unlikely explanation of the enhanced restoration of muscle function and a strong trend for lower serum protein carbonylation.…”

Cocoa, Blood Pressure, and Vascular Function

“…Animal studies demonstrated that CFs are able to decrease cardiac post-ischemic damage via prevention of the mitochondrial permeability transition pore opening, and reduction in superoxide production ( 104 ); flavanols might also affect mitochondrial structure and function via stimulation of mitochondrial biogenesis ( 105 ). Patients, randomized to receive dark chocolate, showed increased maximal oxygen uptake and maximum work achieved, as well as increases in mitochondrial activity and glutathione levels, when compared to placebo ( 106 ). NO is suspected to mediate the effects of cocoa on mitochondria.…”