The Science

The educational framework used by JustProtein is informed by peer-reviewed research in muscle physiology, aging, protein metabolism, and women’s health. All references below are publicly available scientific publications.

This content is provided for educational purposes only and does not constitute medical advice.

Why protein needs change after 40

  • Why age-related muscle loss accelerates after midlife

  • Why the same protein intake no longer triggers muscle repair

    • Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. Cuthbertson D, Smith K, Babraj J, et al. FASEB Journal (2005). https://doi.org/10.1096/fj.04-2640fje

    • The response of muscle protein anabolism to combined hyperaminoacidemia and glucose-induced hyperinsulinemia is impaired in the elderly. Volpi E, Mittendorfer B, Rasmussen BB, Wolfe RR. Journal of Clinical Endocrinology & Metabolism (2000). https://doi.org/10.1210/jcem.85.12.7021

    • Alterations in human muscle protein metabolism with aging: protein and exercise as countermeasures. Churchward-Venne TA, Breen L, Phillips SM. BioFactors (2014). https://doi.org/10.1002/biof.1138

Muscle: a longevity powerhouse

  • Why preserving muscle matters beyond appearance

  • How muscle mass influences blood sugar, metabolism, and aging

Protein quantity vs protein quality

  • Why minimum requirements don’t equal optimal muscle support

  • Why essential amino acids and digestibility matter

  • Why leucine plays a key role in activating muscle repair

    • A high proportion of leucine is required for optimal stimulation of muscle protein synthesis in the elderly. Katsanos CS, Kobayashi H, Sheffield-Moore M, et al. American Journal of Physiology – Endocrinology and Metabolism (2006). https://doi.org/10.1152/ajpendo.00488.2005

    • Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. Norton LE, Layman DK. Journal of Nutrition (2006). https://doi.org/10.1093/jn/136.2.533S

    • Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men. Churchward-Venne TA, Breen L, Di Donato DM, et al. American Journal of Clinical Nutrition (2014). https://doi.org/10.3945/ajcn.113.068775

Why protein distribution matters

  • How per-meal protein intake affects muscle protein synthesis

    • Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. Mamerow MM, Mettler JA, English KL, et al. Journal of Nutrition (2014). https://doi.org/10.3945/jn.113.185280

    • Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. Areta JL, Burke LM, Ross ML, et al. Journal of Physiology (2013). https://doi.org/10.1113/jphysiol.2012.244897

  • How pre- and post-workout protein timing affects muscle protein synthesis

  • What intermittent fasting / time-restricted eating means for lean mass when lifting

    • Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. Moro T, Tinsley G, Bianco A, et al. Journal of Translational Medicine (2016). https://pubmed.ncbi.nlm.nih.gov/27737674/

    • The Effects of Intermittent Fasting Combined with Resistance Training on Lean Body Mass: A Systematic Review of Human Studies. Keenan S, Cooke MB, Belski R. Nutrients (2020). https://pubmed.ncbi.nlm.nih.gov/32781538/

    • Effects of intermittent fasting combined with resistance training on body composition: a systematic review and meta-analysis. Ashtary-Larky D, et al. (2021). https://pubmed.ncbi.nlm.nih.gov/33984329/

Women, Hormones & Muscle

  • Why muscle loss accelerates during midlife hormonal transition

    • Role of menopausal transition and physical activity in loss of lean and muscle mass: A follow-up study in middle-aged Finnish women. Juppi HK, Sipilä S, Cronin NJ, et al. Journal of Clinical Medicine (2020). ttps://pubmed.ncbi.nlm.nih.gov/32456169/

    • Muscle and bone mass in middle-aged women: role of menopausal status and physical activity.
      Sipilä S, Törmäkangas T, Sillanpää E, et al. Journal of Cachexia, Sarcopenia and Muscle (2020). https://pubmed.ncbi.nlm.nih.gov/32017473/

    • Sarcopenia and muscle function during menopause and hormone-replacement therapy. Dionne IJ, Kinaman KA, Poehlman ET. Sports Medicine (2000). https://pubmed.ncbi.nlm.nih.gov/10936902/

  • How estrogen influences muscle strength, repair, and regeneration

    • Estradiol’s beneficial effect on murine muscle function is independent of muscle activity. Greising SM, Baltgalvis KA, Kosir AM, et al. Journal of Applied Physiology (2011). https://pubmed.ncbi.nlm.nih.gov/20966194/

    • Skeletal muscle action of estrogen receptor α is critical for the maintenance of mitochondrial function and metabolic homeostasis in females. Ribas V, Drew BG, Zhou Z, et al. Science Translational Medicine (2016). https://pubmed.ncbi.nlm.nih.gov/27075628/

    • Deletion of estrogen receptor α in skeletal muscle results in impaired contractile function in female mice. Collins BC, Laakkonen EK, Lowe DA, et al. Journal of Applied Physiology (2018). https://pubmed.ncbi.nlm.nih.gov/29345963/

  • Why “one-size-fits-all” protein guidance fails women

    • Protein Requirements of Pre-Menopausal Female Athletes: Systematic Literature Review. Mercer D, Convit L, Condo D, et al. Nutrients (2020). https://pubmed.ncbi.nlm.nih.gov/33207749/

    • Dietary protein requirement of female adults >65 years determined by the indicator amino acid oxidation technique is higher than current recommendations. Rafii M, Chapman K, Owens J, et al. The Journal of Nutrition (2015). https://pubmed.ncbi.nlm.nih.gov/25320185/

    • Changes in muscle mass and strength after menopause. Maltais ML, Desroches J, Dionne IJ. Current Opinion in Clinical Nutrition and Metabolic Care (2009). https://pubmed.ncbi.nlm.nih.gov/19949277/