references
  
      National Institute of Health: "Vitamin D"
    
      Medicine & Science in Sports & Exercise: "Independent and combined effects of amino acids and glucose after resistance exercise"
    
      Encyclopedia of Food and Health: "Casein and Caseinate: Methods of Manufacture"
    
      Endocrinology and Metabolism: "The digestion rate of protein is an independent regulating factor of postprandial protein retention"
    
      Endocrinology and Metabolism: "Whey and casein labeled with L-[1-13C]leucine and muscle protein synthesis: effect of resistance exercise and protein ingestion"
    
      Nutrients: "The Potential Role of Creatine in Vascular Health"
    
      Cureus: "Efficacy and Tolerability of Ashwagandha Root Extract in the Elderly for Improvement of General Well-being and Sleep: A Prospective, Randomized, Double-blind, Placebo-controlled Study"
    
      Physiological Reports: "The effect of acute sleep deprivation on skeletal muscle protein synthesis and the hormonal environment"
    
      Hormone and Metabolic Research: "Effect of vitamin D supplementation on testosterone levels in men"
    
      Journal of Clinical Endocrinology and Metabolism: "Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial"
    
      European Journal of Applied Physiology: "Effects of chronic beetroot juice supplementation on maximum oxygen uptake, velocity associated with maximum oxygen uptake, and peak velocity in recreational runners: a double-blinded, randomized and crossover study"
    
      Journal of the International Society of Sports Nutrition: "Phosphatidic acid supplementation increases skeletal muscle hypertrophy and strength"
    
      National Library of Medicine: "Ashwagandha"
    
      MedlinePlus: "Protein in Diet"
    
      Cleveland Clinic: "Is Whey Protein Good for You?"
    
      Journal of the International Society of Sports Nutrition: "How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution"
    
      U.S. National Library of Medicine: "Amino Acids"
    
      American Dairy Products Institute: "Milk Protein Isolate"
    
      Nutrition & Metabolism: "Phosphatidic acid: biosynthesis, pharmacokinetics, mechanisms of action and effect on strength and body composition in resistance-trained individuals"
    
      International Journal of Exercise Science: "Casein Protein Supplementation in Trained Men and Women: Morning versus Evening"
    




Research into the best supplements for muscle growth is still evolving, so follow this guide and our expert-backed criteria to pick the best product for you.

Image Credit: lakshmiprasad S/iStock/GettyImages

Image Credit: lakshmiprasad S/iStock/GettyImages

  • How We Chose
  • Whey
  • Casein
  • Creatine
  • Ashwagandha
  • Vitamin D
  • What to Look For
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      National Institute of Health: "Vitamin D"
    
      Medicine & Science in Sports & Exercise: "Independent and combined effects of amino acids and glucose after resistance exercise"
    
      Encyclopedia of Food and Health: "Casein and Caseinate: Methods of Manufacture"
    
      Endocrinology and Metabolism: "The digestion rate of protein is an independent regulating factor of postprandial protein retention"
    
      Endocrinology and Metabolism: "Whey and casein labeled with L-[1-13C]leucine and muscle protein synthesis: effect of resistance exercise and protein ingestion"
    
      Nutrients: "The Potential Role of Creatine in Vascular Health"
    
      Cureus: "Efficacy and Tolerability of Ashwagandha Root Extract in the Elderly for Improvement of General Well-being and Sleep: A Prospective, Randomized, Double-blind, Placebo-controlled Study"
    
      Physiological Reports: "The effect of acute sleep deprivation on skeletal muscle protein synthesis and the hormonal environment"
    
      Hormone and Metabolic Research: "Effect of vitamin D supplementation on testosterone levels in men"
    
      Journal of Clinical Endocrinology and Metabolism: "Vitamin D and Testosterone in Healthy Men: A Randomized Controlled Trial"
    
      European Journal of Applied Physiology: "Effects of chronic beetroot juice supplementation on maximum oxygen uptake, velocity associated with maximum oxygen uptake, and peak velocity in recreational runners: a double-blinded, randomized and crossover study"
    
      Journal of the International Society of Sports Nutrition: "Phosphatidic acid supplementation increases skeletal muscle hypertrophy and strength"
    
      National Library of Medicine: "Ashwagandha"
    
      MedlinePlus: "Protein in Diet"
    
      Cleveland Clinic: "Is Whey Protein Good for You?"
    
      Journal of the International Society of Sports Nutrition: "How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution"
    
      U.S. National Library of Medicine: "Amino Acids"
    
      American Dairy Products Institute: "Milk Protein Isolate"
    
      Nutrition & Metabolism: "Phosphatidic acid: biosynthesis, pharmacokinetics, mechanisms of action and effect on strength and body composition in resistance-trained individuals"
    
      International Journal of Exercise Science: "Casein Protein Supplementation in Trained Men and Women: Morning versus Evening"