The International Society of Sports Nutrition critically reviewed the current scientific literature on protein intake for healthy exercising adults. Their conclusion: “Increasing protein intake by consuming whole foods as well as high-quality supplemental protein sources can improve the adaptive response to training”.
The position statement of the International Society of Sports Nutrition (ISSN) is an extensive overview of the current literature on protein, exercise and sports nutrition for healthy exercising adults. In this article we sum up the 13 key recommendations of the ISSN published in their latest position statement (Jager et al., 2017).
1. Exercise and protein for optimal Muscle Protein Synthesis (MPS)
An acute exercise stimulus, particularly resistance exercise, and protein ingestion both stimulate muscle protein synthesis (MPS) and are synergistic when protein consumption occurs before or after resistance exercise.
2. Recommended protein intake is 1.4-2.0 g/kg/d
For building muscle mass and for maintaining muscle mass through a positive muscle protein balance, an overall daily protein intake in the range of 1.4–2.0 g protein/kg body weight/day is sufficient for most exercising individuals, a value that falls in line within the Acceptable Macronutrient Distribution Range published by the Institute of Medicine for protein.
3. Novel evidence: protein intake >3.0 g/kg/d
There is novel evidence that suggests that higher protein intakes (>3.0 g/kg/d) may have positive effects on body composition in resistance-trained individuals (i.e., promote loss of fat mass).
4. Optimum intake per serving: 20-40 gram protein
Recommendations regarding the optimal protein intake per serving for athletes to maximize MPS are mixed and are dependent upon age and recent resistance exercise stimuli. General recommendations are 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g.
5. Acute protein doses: 700-3000 mg of leucine
Acute protein doses should strive to contain 700–3000 mg of leucine and/or a higher relative leucine content, in addition to a balanced array of the essential amino acids (EAAs).
6. Protein doses every 3-4 hour
These protein doses should ideally be evenly distributed, every 3–4 h, across the day.
7. Anabolic effect of exercise is long-lasting
The optimal time period during which to ingest protein is likely a matter of individual tolerance, since benefits are derived from pre- or post-workout ingestion; however, the anabolic effect of exercise is long-lasting (at least 24 h), but likely diminishes with increasing time post-exercise.
8. Supplements can ensure protein intake
While it is possible for physically active individuals to obtain their daily protein requirements through the consumption of whole foods, supplementation is a practical way of ensuring intake of adequate protein quality and quantity, while minimizing caloric intake, particularly for athletes who typically complete high volumes of training.
9. Essential Amino Acids are most effective for MPS
Rapidly digested proteins that contain high proportions of essential amino acids (EAAs) and adequate leucine, are most effective in stimulating muscle protein synthesis.
10. Advise high-quality protein supplements
Different types and quality of protein can affect amino acid bioavailability following protein supplementation.
11. Focus on whole foods with all essential amino acids
Athletes should consider focusing on whole food sources of protein that contain all of the EAAs (i.e., it is the EAAs that are required to stimulate MPS).
12. Endurance athletes should primarily focus on carbohydrate intake
Endurance athletes should focus on achieving adequate carbohydrate intake to promote optimal performance; the addition of protein may help to offset muscle damage and promote recovery.
13. Casein based proteins before sleep
Pre-sleep casein protein intake (30–40 g) provides increases in overnight muscle protein synthesis and metabolic rate without influencing lipolysis.