The International Society of Sports Nutrition (ISSN) provides a comprehensive and objective review of protein intake for healthy, exercising individuals. Based on the latest scientific literature, the ISSN highlights the importance of protein in stimulating muscle protein synthesis (MPS), particularly when consumed before or after resistance exercise. The ISSN emphasizes the practicality of protein supplementation, the significance of protein quality and bioavailability, and specific recommendations for endurance athletes and pre-sleep protein consumption to enhance recovery and performance.

The Key Points:

1. Muscle Protein Synthesis (MPS) Stimulation:
   • Both acute exercise (particularly resistance exercise) and protein ingestion stimulate MPS.
   • Consuming protein before or after resistance exercise enhances this effect synergistically.
2. Daily Protein Intake for Muscle Mass:
   • For building and maintaining muscle mass, a daily intake of 1.4-2.0 g/kg of body weight is sufficient for most exercising individuals.
   • This range aligns with the Acceptable Macronutrient Distribution Range published by the Institute of Medicine.
3. Higher Protein Intakes During Hypocaloric Periods:
   • Resistance-trained individuals may need higher protein intakes (2.3-3.1 g/kg/day) to maximize lean body mass retention during periods of calorie restriction.
4. Positive Effects of Very High Protein Intake:
   • Emerging evidence suggests that protein intakes above 3.0 g/kg/day may promote fat mass loss in resistance-trained individuals.
5. Optimal Protein Intake per Serving:
   • Recommendations vary based on age and recent exercise stimuli, generally suggesting 0.25 g of high-quality protein per kg of body weight or an absolute dose of 20-40 g per serving.
   • Protein doses should aim to contain 700-3000 mg of leucine and a balanced array of essential amino acids (EAAs).
6. Distribution of Protein Intake:
   • Protein intake should be evenly distributed every 3-4 hours throughout the day.
7. Timing of Protein Ingestion:
   • The optimal timing for protein ingestion depends on individual tolerance, with benefits seen from both pre- and post-workout consumption.
   • The anabolic effect of exercise on MPS is long-lasting (at least 24 hours), though it diminishes over time post-exercise.
8. Protein Supplementation:
   • While whole foods can meet daily protein requirements, supplementation is practical for ensuring adequate protein intake, especially for athletes undergoing high volumes of training.
   • Rapidly digested proteins with high EAA content and adequate leucine are most effective for stimulating MPS.
9. Types and Quality of Protein:
   • The bioavailability of amino acids can be affected by the type and quality of protein.
   • Athletes should focus on whole food sources of protein containing all EAAs necessary to stimulate MPS.
10. Carbohydrate and Protein Intake for Endurance Athletes:
    • Endurance athletes should prioritize adequate carbohydrate intake for optimal performance.
    • Adding protein can help offset muscle damage and promote recovery.
11. Pre-Sleep Protein Intake:
    • Consuming 30-40 g of casein protein before sleep can increase overnight MPS and metabolic rate without affecting lipolysis.

Conclusion

The ISSN’s position on protein intake provides valuable guidance for healthy, exercising individuals seeking to optimize their muscle health and performance. By recommending specific protein intake levels, both daily and per serving, the ISSN highlights the critical role of protein in muscle protein synthesis, recovery, and body composition. The Society’s guidelines emphasize the importance of timing, distribution, and quality of protein intake, offering practical advice on supplementation and whole food sources. For endurance athletes, the combination of adequate carbohydrates and protein is essential for performance and recovery. Additionally, pre-sleep protein intake can support overnight muscle synthesis and metabolic rate. Following these evidence-based recommendations can help individuals effectively meet their protein needs, enhance their training outcomes, and achieve their fitness goals.

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