Effect of Dark Chocolate Supplementation on Tissue Oxygenation, Metabolism, and Performance in Trained Cyclists at Altitude

Abstract

Dark chocolate (DC) is high in flavonoids and has been shown to increase nitric oxide in the blood. Increased nitric oxide has the potential to improve delivery of oxygen to muscle, especially in hypoxic conditions, such as altitude. Our aim was to assess the impact of DC supplementation on cycling performance at altitude. Twelve healthy, trained cyclists (n = 2 females, n = 10 males; age = 35 [12] years; height = 177 [7] cm; mass = 75.2 [11.0] kg; VO2max = 55 [6] ml·kg−1·min−1) were randomized to supplement with 60 g of DC or placebo twice per day for 14 days in a double-blind crossover study. After the 2 weeks of supplementation, the participants attended a laboratory session in which they consumed 120 g of DC or placebo and then cycled for 90 min at 50% peak power output, followed immediately by a 10-km time trial (TT) at simulated altitude (15% O2). The plasma concentration of blood glucose and lactate were measured before and at 15, 30, 60, and 90 min during the steady-state exercise and post TT, while muscular and prefrontal cortex oxygenation was measured continuously throughout exercise using near-infrared spectroscopy. DC resulted in a higher concentration of blood glucose (5.5 [0.5] vs. 5.3 [0.9] mmol/L) throughout the trial and lower blood lactate concentration following the TT (7.7 [1.92] vs. 10.0 [4.6] mmol/L) compared with the placebo. DC had no effect on the TT performance (19.04 [2.16] vs. 19.21 ± 1.96 min) or oxygenation status in either the prefrontal cortex or muscle. The authors conclude that, although it provided some metabolic benefit, DC is not effective as an ergogenic aid during TT cycling at simulated altitude.

Self-Paced Endurance Performance and Cerebral Hemodynamics of the Prefrontal Cortex: A Scoping Review of Methodology and Findings

“…Therefore, all distances selected were around or just above distances commonly adopted in neuroscience more broadly and sport science research specifically. However, two studies did not report a source-detector separation distance ( Liao et al, 2019 ; Shaw et al, 2020 ).…”

“…A noted exception is the use of a standing baseline in one study where the exercise task required treadmill running ( Billaut et al, 2010 ). However, a seated baseline was conducted in two studies also using a running task ( Santos-Concejero et al, 2015 ; Shaw et al, 2020 ).…”

“…Ten studies opted to place fNIRS optodes over the dorsolateral PFC, corresponding to Fp1-F3 and Fp2-F4 regions according to the international EEG 10-20 system ( Billaut et al, 2010 ; Bourdillon et al, 2014 ; Decroix et al, 2016 , 2018 ; Liao et al, 2019 ; Pires et al, 2016 ; Robertson et al, 2016 ; Santos-Concejero et al, 2015 ; Wingfield et al, 2018 , 2019 ). Three studies did not reference a particular brain ROI but did provide anatomical measurements for determining optode placement ( Ferguson et al, 2018 ; Shannon et al, 2017 ; Shaw et al, 2020 ), while four further studies did not provide such measurements ( Fan et al, 2013 , 2018 ; Hamlin et al, 2010 ; Nielsen et al, 1999 ). It should be noted that research objectives may dictate the necessity to highlight a ROI.…”

“…Although cocoa flavanol intake raised PFC oxygenation levels at rest, no differences were observed in TT performance or oxygenation levels during exercise. Most recently, Shaw et al (2020) used trained cyclists to assess the impact of 14-day dark chocolate (high in flavonoids) intake on 10 km TT performance at simulated altitude. Although some metabolic benefits to dark chocolate intake were observed, no benefits to PFC oxygenation or performance were found.…”

Evaluation of total polyphenols content and antioxidant capacity of different commercial cocoa (theobroma cacao) powders) / Avaliação do teor de polifenóis totais e capacidade antioxidante de diferentes pós comerciais de cacau (theobroma cacao)

“…In contrast with this idea, no significant difference in polyphenols among the non-organic brands of natural cocoa powder was found. Cocoa and cocoa products, including cocoa liquor, cocoa powder, and chocolate (dark chocolate and milk), are highly consumed due to its variety of polyphenols content and different levels of antioxidant proprieties (LUDOVICI et al, 2017 REES et al, 2018;SHAW et al, 2020). Typically, the total polyphenols content in the cocoa powder products are not informed on the label, which make it difficult to establish recommendations about how much cocoa powder is necessary to provide an optimal amount of polyphenols.…”