Multiday Pomegranate Extract Supplementation Decreases Oxygen Uptake During Submaximal Cycling Exercise, but Cosupplementation With N-acetylcysteine Negates the Effect

Abstract

Pomegranate extract (POMx) has been suggested as an ergogenic aid due to its rich concentration of polyphenols, which are proposed to enhance nitric oxide bioavailability, thereby improving the efficiency of oxygen usage and, consequently, endurance exercise performance. Although acute POMx supplementation improves aerobic exercise performance in untrained individuals, trained athletes appear to require chronic supplementation for a similar effect. Furthermore, the combination of POMx with a thiol antioxidant may prove more effective than POMx alone, due to the protective effects of thiols on nitric oxide. Thus, this study hypothesized that multiday POMx supplementation would decrease the oxygen uptake (VO) required by trained cyclists to perform submaximal exercise and increase performance during a time trial, and that thiol (N-acetylcysteine [NAC]) cosupplementation would enhance these effects. Eight cyclists completed four 8-day supplementation periods: POMx only, NAC only, POMx + NAC (BOTH), and placebo. Following supplementation, they performed submaximal cycling and a 5-min time trial, with VO and muscle oxygen saturation (SmO) being recorded. A three-way (POMx × NAC × Intensity) repeated-measures analysis of variance with a Fisher's least significant difference post hoc assessment was performed for dependent variables (p ≤ .05). VO during submaximal exercise was reduced with POMx versus placebo (-2.6 ml·min·kg, p = .009) and BOTH (-2.5 ml·min·kg, p < .05) and increased with NAC (+1.9 ml·min·kg, p < .03), despite no main effect of treatment on SmO or performance. It appears that POMx's high polyphenol content reduced the VO required during submaximal exercise. However, NAC cosupplementation annulled this effect; thus, NAC may interact with nitric oxide to reduce its bioavailability.

Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials

“…As shown in Additional Material 3, only five polyphenol studies included a direct measure of nitric oxide status (e.g. plasma NO 3 - or NO 2 - ), with only one study [ 149 ] demonstrating a significant increase in any of these biomarkers (plasma NO 3 - ) following polyphenol (pomegranate) consumption. Similarly, only 14 polyphenol studies investigated effects on vascular parameters such as flow-mediated dilation (FMD) and blood pressure.…”

Pomegranate Extract Improves Maximal Performance of Trained Cyclists after an Exhausting Endurance Trial: A Randomised Controlled Trial

“…NO regulates physiological functions and has been recognized as an important factor in endothelial vascular relaxation during exercise [46,47,48] which also increases muscle blood flow [49]. Pomegranate significantly increase plasma nitrate (NO 3 ) when supplemented for 8 days [50]. In addition, other polyphenol-rich supplements can produce a similar vasodilatation and contribution to NO pathways [51].…”

How N-Acetylcysteine Supplementation Affects Redox Regulation, Especially at Mitohormesis and Sarcohormesis Level: Current Perspective

“…However, there is limited research investigating these possible mechanisms in athletes. One study investigating the influence of multi-day pomegranate extract co-supplemented with NAC in male cyclists rejected the study hypothesis that it originally suggested, suggesting that co-supplementation may impair exercise performance by enhancing the formation of SNO, thus reducing NO bioavailability [113]. Further studies are needed to be elucidated the exact influence of possible interactions.…”