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Whole-body protein utilization in humans.
1Department of Nutritional Sciences, University of California at Berkeley 94720.
Medicine and Science in Sports and Exercise
|October 1, 1987
Summary
High protein intake recommendations for athletes may be premature. Insufficiently controlled variables like training adaptation, energy balance, and exercise intensity impact nitrogen balance and protein needs.
Area of Science:
- Exercise Physiology
- Nutritional Science
- Sports Nutrition
Background:
- Recent recommendations suggest high protein intake (2-3 g/kg/day) for physically active individuals.
- Existing research supporting these recommendations may be limited by uncontrolled variables.
Purpose of the Study:
- To critically evaluate the scientific literature supporting high protein intake recommendations for athletes.
- To identify key variables that influence protein requirements in active populations.
Main Methods:
- Literature review of studies investigating protein intake and nitrogen balance in exercising individuals.
- Analysis of factors including training adaptation period, energy balance, and exercise intensity.
Main Results:
- A 12-14 day adaptation period is observed post-exercise initiation, during which nitrogen balance is negative.
- Moderate exercise (40-50% VO2max) can promote nitrogen retention with sufficient adaptation time and marginal protein intake.
- High-intensity exercise (64% VO2max) with negative energy balance may render even high protein intake (2 g/kg/day) insufficient for nitrogen equilibrium.
Conclusions:
- Current high protein intake recommendations for athletes are premature due to insufficient control of key variables.
- Exercise intensity, energy balance, and training status significantly modulate protein requirements.
- Further research is needed to establish precise protein recommendations considering these interacting factors.