Proteins in sports nutrition

Peer-Reviewed / reviewed during preparation

Position of the working group sports nutrition of the German Nutrition Society (DGE)

Introduction

For the human body, adequate protein intake is crucial. Proteins are essential building blocks for the structure and metabolism of muscle, bone, and connective tissue. Proteins and amino acids also play key roles in cell metabolism, hormonal balance, the immune system, the coagulation system and energy metabolism [1–3]. With regard to possible effects in the field of sport, proteins are frequently reported to have positive effects on muscle protein synthesis, muscle mass, muscle strength, improvement in body composition, prevention of a catabolic state, immunocompetence and ensuring optimal regeneration in the post-exertion phase [1, 4–6].

To achieve these aims, not only is an adequate quantity of protein required, but also an adequately high quality of protein [3, 7]. Although various meta-analyses have been published on this topic, not all questions regarding quantity and quality of protein sources and amino acid composition have been definitively answered. In addition, it is increasingly being discussed whether it is a protein's composition in terms of individual amino acids that determines effectiveness, or whether di-, trior oligopeptides with specific signalling effects on cellular regulation also play a role in the muscular adaptation process [3, 8–10].

What is clear and undisputed is that measurable results can only be obtained through a combination of training and protein intake [11, 12]. Simply increasing protein intake without changing training activities will not result in any structural or metabolic adaptations.

Abstract

Adequate intake of high quality proteins and amino acids is essential for the body in order to synthesize structures such as muscle, tendons, ligaments, and bone. Protein intake also regulates and affects various metabolic processes, including hormonal regulation. Accordingly, proteins and amino acids are, to varying extents, able to stimulate or inhibit anabolic signal transduction pathways and the synthesis and secretion of various hormones such as insulin, growth hormone, and insulin-like growth factor 1 (IGF-1).
This means that tailoring protein intake to an athlete’s specific type of sport and exercise intensity can be helpful in supporting the training process and improving performance. The aims of adjusting intake in this way may include maintaining or building muscle mass or muscle strength, preventing a catabolic state, and improving recovery following exercise.
Even though the importance of protein intake in the field of sport is increasingly well-known, there is still much controversy regarding intake levels, types of protein sources, optimal amino acid composition, and ideal timing of intake. The lay press and commercial websites in particular often give biased or incorrect recommendations without any supporting scientific evidence.
This position paper sets out the current state of knowledge regarding the physiological effects of protein intake in sports, paying particular attention to the aspects of intake level and the dose-response relationship.

Keywords: proteins, sports nutrition, recommended intake, muscle mass, regeneration

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