In theory: how much protein do sportspeople need?

A number of questions need to be answered before nutritional advice can be given to an athlete. How much fuel (energy) does a sportsperson need? Which fuels are preferred? What about the proportion between carbohydrate, fat and protein? What roles do the vitamins and minerals play? In this article more information on the protein recommendations.

Proteins are essential for a number of processes in the body, including the growth and maintenance of muscles. (EFSA 2010 and 2011) Proteins consist of long chains of amino acids and for each protein the amino acid chain is unique. The essential amino acids are important for protein synthesis. As the body cannot produce them itself, they must be obtained from the food we eat. (1-4) When there is an insufficient quantity of an essential amino acids present, protein synthesis may be compromised. An optimum protein intake for an athlete is an intake that is sufficient to:

• provide all the essential amino acids;
• maintain an optimum protein synthesis for development and maintenance of muscle mass;
• support the body processes in which amino acids play a role. (2)

Maintenance and development of muscle mass

Just like all other organs in the body, the muscles are renewed on a daily basis. This means that a regular maintenance process of muscle protein breakdown and muscle protein synthesis takes place, known as protein turnover. In order to support muscle growth and development, muscle protein synthesis must be greater than muscle protein breakdown. Exercise training stimulates muscle protein synthesis and is important for development of muscle mass, strength and power. Training and exercise actually causes some damage to the muscle fibres which stimulates their recovery and makes them stronger. (5)

Protein needs athlete

Athletes generally have a larger muscle mass to maintain and may be training to increase their lean mass. Intensive resistance exercise is also associated with muscle fibre damage and so athletes and sportspeople require more protein for muscle repair and regeneration than the general population. These additional protein requirements depend on multiple factors. Generally endurance athletes have a slight to moderate increased protein requirement, whereas the advice for strength athletes is twice that of the general population. The most recent advice from the Academy of Nutrition and Dietetics, Dieticians of Canada and the American College of Sports Medicine (6) advises that protein requirements are dependent on, training status (well-trained athletes need a somewhat smaller quantity than less well-trained athletes) and the intensity of the training (the higher the frequency and the intensity, the higher the requirement).

TABLE Recommended protein intake

Eating more protein than the recommended amounts is not helpful in terms of muscle development. Unlike fats and carbohydrates, proteins are not stored in the body. When more protein is eaten than the capacity to synthesise muscle protein, the ‘excess’ protein is simply used as energy source. Also when insufficient carbohydrates are available and/ or energy intake is low, e.g. in sports in which weight plays an important role, protein is used as an energy source and therefore cannot be used for muscle protein synthesis (6). When the diet matches the athlete’s energy requirements it will usually also contain a sufficient amount of protein.

FIGURE Muscle protein synthesis after exercising for different portions of protein

Timing of protein

Research has shown that apart from the total quantity of protein, the distribution of the protein intake over the entire day is equally important for muscle protein synthesis. To optimise muscle protein synthesis it is recommended to divide the total daily requirement for protein over four to six eating occasions in portions of 0.25-0.3 g protein/kg body weight. In practice this comes down to about 20 grams of protein per meal/snack, as breakfast, lunch, dinner, post- exercise and just before going to sleep. This pattern of protein distribution over the day can enhance muscle growth compared to the total protein requirement is consumed in two or three larger portions or over several smaller portions during the day. (6-8)

Protein synthesis during the night

Apart from the traditional eating occasions, consuming protein during the recovery period after training or a match is a priority, because heavy exercise stimulates muscle protein synthesis and recovery (9). Also consuming a portion of protein just before going to sleep may stimulate muscle protein synthesis during the night and so helps to optimise the opportunity for recovery overnight. (10-11) Typically muscle protein synthesis decreases during the night, as the regular muscle protein breakdown continues which results in a negative protein balance in the body in the morning. When athletes consume a portion of protein just before going to sleep, they may benefit from a positive protein balance in the body the next morning, as demonstrated by Res et al., (2012). In this study consuming 40 grams of casein before going to sleep increased the protein synthesis by 22% during the night (10).

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References

1. Cuthbertson D., Smith K., Babraj J., Leese G., Waddell T., Atherton P., Wackerhage H., Taylor P.M., Rennie M.J. (2005) Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. The FASEB Journal. 2005;19:422–424.
2. Phillips S.M. (2012). Dietary protein requirements and adaptive advantages in athletes. British Journal of Nutrition. 2012;108:S158-S167. doi:10.1017/S0007114512002516. Pritchett K., Pritchett R. (2012). Chocolate milk: a post-exercise recovery beverage for endurance sports. Medicine & Science in Sports & Exercise. 2012;59:127-34. doi: 10.1159?000341954. Epub 2012 Oct 15.
3. Tipton K.D., Gurkin B.E., Matin S., Wolfe R.R. (1999) Nonessential amino acids are not necessary to stimulate net muscle protein synthesis in healthy volunteers. Journal Of Nutritional Biochemistry. 1999;10:89–95.
4. Volpi E., Kobayashi H., Sheffield-Moore M., Mittendorfer B., Wolfe R.R. (2003) Essential amino acids are primarily responsible for the amino acid stimulation of muscle protein anabolism in healthy elderly adults. American Journal of Clinical Nutrition. 2003;78:250–258.
5. Silverthorn D.U. (2010) Human Physiology, an integrated approach. Pearson International Edition, fifth edition 2010 (ISBN 13:978-0-321-60061-5).
6. American College of Sports Medicine, Academy of Nutrition and Dietetics and Dietitians of Canada. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 2016; 116: 501-528.
7. Areta J.L., Burke L.M., Ross M.L, Camera D.M., West D.W., Jeacocke N.A., Moore D.R., Stellingwerff t., Phillips S.M., Hawley J.A., Coffey V.G. (2013). Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. The Journal of Physiology. 2013;591(Pt 9):2319-31.
8. Moore D.R., Robinson M.J., Fry J.L., Tang J.E., Glover E.I., Wilkinson S.B., Prior T., Tarnopolsky M.A., Phillips S.M. (2009). Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise response of muscle and albumin protein synthesis after resistance exercise in young men. American Journal of Clinical Nutrition. 2009;89:161-168.
9. Beelen et al., 2010
10. Res P.T., Groen B., Pennings B., Beelen M., Wallis G.A., Gijsen A.P., Senden J.M., van Loon L.J. (2012). Protein ingestion before sleep improves postexercise overnight recovery. Medicine & Science in Sports & Exercise. 2012;44:1560-1569
11. Snijders T. (2014). Satellite cells in skeletal muscle atrophy and hypertrophy. Maastricht University, 2014.