Does Epicatechin Help Build Muscle and Strength?

Introduction and Proposed Mechanisms

Epicatechin, a monomeric flavan-3-ol found in cacao (Theobroma cacao) and green tea (Camellia sinensis), has garnered interest as an ergogenic and anabolic compound [4]. In preclinical models, epicatechin modulates skeletal muscle proteostasis by suppressing myostatin—a negative regulator of muscle growth—and downregulating muscle atrophy-related E3 ubiquitin ligases and transcription factors, including MAFbx (atrogin-1), MuRF1, and FOXO [3, 4]. Simultaneously, it upregulates follistatin (an endogenous myostatin antagonist), stimulates myogenic regulatory factors such as MyoD, Myf5, and myogenin, and activates the IGF-PI3K-AKT/mTOR signaling pathway responsible for muscle protein synthesis [3, 4].

Beyond pathways governing hypertrophy, epicatechin uniquely promotes mitochondrial biogenesis and capillary angiogenesis in skeletal muscle fibers compared to other catechin subclasses [3, 4]. These physiological mechanisms have positioned epicatechin as a potential candidate for enhancing resistance training adaptations, improving strength, and shifting the circulating follistatin-to-myostatin balance [3]. However, translating these mechanistic findings to resistance-trained human athletes reveals conflicting and population-dependent outcomes [4, 5].

Acute Pilot Data in Humans

Early interest in epicatechin's anabolic efficacy was driven by a proof-of-concept human pilot investigation [6, 8]. In this trial, six middle-aged subjects (mean age 41 ± 5 years) consumed 25 mg of pure (-)-epicatechin twice daily (~1 mg/kg/day) for 7 days [6]. The protocol produced a 49.2 ± 16.6% increase in the plasma follistatin-to-myostatin ratio and a concurrent ~7% increase in bilateral isometric handgrip strength [6, 8, 11].

Complementary preclinical data in young (6-month) and aged (26-month) C57BL/6 mice receiving 1 mg/kg twice daily demonstrated significant decreases in skeletal muscle myostatin (-15% and -21%, respectively) and a 56% increase in follistatin in aged muscle, alongside reductions in senescence-associated markers [6, 8]. Although these findings confirmed bioavailability and acute endocrine modulation, the sample size was minimal (n=6), uncontrolled for training status, and lacked a randomized control group [6].

Evidence in Sarcopenic and Clinical Cohorts

The strongest clinical evidence for combined resistance training and epicatechin supplementation stems from an 8-week double-blind randomized controlled trial conducted by Mafi et al. (2019) in 62 sarcopenic older males (mean age 68.63 ± 2.86 years) [1]. Participants were allocated across four parallel groups: resistance training alone (RT), epicatechin alone (EP), combined resistance training and epicatechin (RT+EP), or placebo (PL) [1].

The RT+EP intervention produced superior outcomes compared to all other conditions [1]:

• Follistatin and Myostatin: The RT+EP group achieved the largest significant increases in plasma follistatin and the follistatin-to-myostatin ratio [1]. Plasma myostatin decreased significantly only in the RT+EP and RT cohorts [1].
• Strength Outcomes: Gains in upper-body (chest press) and lower-body (leg press) maximal strength were significantly greater in the RT+EP group than in RT alone, EP alone, or placebo [1].
• Functional and Morphological Metrics: Appendicular muscle mass index (AMMI) and Timed Up and Go (TUG) mobility performance improved significantly across all three active experimental groups relative to placebo [1].

In clinical populations with underlying muscular pathology, such as Becker muscular dystrophy, 8 weeks of oral (-)-epicatechin (100 mg/day) similarly elicited increases in muscle and plasma follistatin, reductions in myostatin, and enhanced mitochondrial biogenesis markers including PGC-1α, LKB1, AMPK, and cristae abundance [10]. However, these populations have elevated baseline myostatin, pronounced muscle wasting, and suppressed myogenic signaling compared to healthy resistance-trained adults [6, 10].

Efficacy in Young, Healthy, and Trained Individuals

Direct transfer of these results to young, resistance-trained individuals is challenged by conflicting clinical data [4, 5]. In a 4-week double-blind randomized controlled trial in 20 recreationally active young adults (aged 18–30), supplementation with 200 mg/day of (-)-epicatechin (100 mg twice daily) combined with cycle training failed to alter skeletal muscle myostatin mRNA expression or protein levels of mitochondrial markers such as cytochrome C and citrate synthase [5].

Moreover, the study observed an apparent interference effect on endurance adaptations: the epicatechin cohort experienced blunted training responses, showing no significant increase in succinate dehydrogenase (SDH; p = 0.81) or relative peak oxygen consumption (VO2 peak; p = 0.21), whereas the placebo training group achieved significant improvements in both SDH (p = 0.03) and VO2 peak (p < 0.01) [5]. While this specific study evaluated cycling rather than dedicated heavy resistance training, the failure to alter myostatin gene expression indicates that epicatechin does not uniformly disrupt myostatin signaling in healthy, younger musculature [5].

Practical Summary for Athletes

Current clinical literature demonstrates a distinct dichotomy in epicatechin outcomes:

1. High Efficacy in Deficient or Sarcopenic Muscle: In older sarcopenic individuals and clinical populations characterized by age-related increases in myostatin and reductions in follistatin, epicatechin acts synergistically with resistance training to amplify strength gains and improve follistatin-to-myostatin ratios [1, 6, 10].
2. Uncertain Hypertrophic Efficacy in Trained Cohorts: In young, healthy individuals, epicatechin has failed to downregulate myostatin mRNA or enhance mitochondrial enzyme adaptation during training [5]. High doses may potentially blunt specific training-induced cellular stress signals necessary for adaptation [5].
3. Lack of Standardized Dosing: While daily doses between 1 mg/kg and 200 mg have been explored in trials, standardized clinical protocols optimizing timing, purity, and pairing with specific resistance training regimens remain unestablished [3, 4].