Protein and sport, the latest scientific evidence
At this point let\'s not repeat, as is done in every blog or opening words of an article, what proteins and amino acids are and what role they play, because now we know they are "letters of an alphabet older than life" (Dioguardi 2008). Instead let’s go directly to the crux of the matter: what is an adequate protein intake for an athlete and amateur athlete?
RDA and IAAO
If we take the latest LARN data (revision IV and reprint II, 2018), we can immediately see that the reference guidelines for the sedentary population are still between 0.71 and 0.9 g total daily protein per kg total body weight, and this is fully justified by IAAO (indicator of amino acids oxidation) detection. The IAAO is a daily protein turnover indicator, i.e. the amount of amino acids required to perform enzyme functions throughout the body and renew muscle structures. In healthy, untrained, young people, this turnover is 0.93 to 1.2 g/kg (Humayun et al. 2007), which means that for a person of 70 kg who is not physically active, the basic amount of protein needed to maintain organ function should be between 65 and 84 g of total daily protein, and not only from noble supplements or purely vegetable sources (we will talk more about this in another dedicated article).
IAAO in Endurance, Bodybuilding and CrossFit® athletes
On the other hand, when it comes to trained sportsmen and women undertaking predominantly performance-oriented activities, the amount of amino acids detected by IAAO is between 2.1 and 2.6 g/kg (Bandegan et al. 2019) in Endurance athletes, and 1.7-2.2 g/kg (Bandegan et al. 2019) in Bodybuilders. This is because we must remember that in athletes undertaking strenuous, endurance exercise (Tour de France, Triathlon, Marathon), the protein turnover is higher precisely because they often start depleting the amino acid stores to get additional glucose into the bloodstream, whereas for those who practise sports for aesthetic purposes, aimed mainly at building and maintaining muscle mass, training is less taxing and the function of the mechanical stimulus is to achieve hypertrophy and try to avoid excessive degradation. The training carried out by body-builders and those doing crossfit, in fact, especially by these individuals, while not done over long periods, is often of such intensity and density as to cause muscle damage and a fairly high protein turnover. However, caution is advised. Although the "turnover" is not to be confused with the "adequate quantity for muscle building", there is not much difference between the two. Indeed, we will see that the recommended intake is very close to these coefficients.
Appropriate intakes for athletes
According to the latest reviews and opinions published in the JISSN (Journal of International Society of Sports Nutrition), the protein intake for athletes who perform taxing activities, whether endurance or power sports, is between:
• 1.6 and 2.2 g protein per kg total body weight per day under normal and hypercaloric conditions (Aragon, Shoenfeld et al, 2017);
• up to 3.1 g/kg/day in the low-calorie phase (Helms, Aragon, Fitschen, 2014)
Obviously, the dietary plan must be assessed by a nutritionist, nutrition biologist or dietician who will be responsible for ensuring that the objectives set by the applicant are achieved according to the established guidelines. Common sense dictates that some objectives require time and dedication, and therefore the patient\'s compliance needs to be taken into account, since athletes or amateur athletes are a specific population and not easily manageable.
Article edited by Edoardo Tacconi - Scientific Disclosure
1. Gli aminoacidi - Dioguardi - © Sintesi Infomedica S.r.l. 2018
2. LARN - © SiNu 2018
3. Humayun MA, Elango R, Ball RO, Pencharz PB. Reevaluation of the protein requirement in young men with the indicator amino acid oxidation technique. Am J Clin Nutr. 2007 Oct;86(4):995-1002. PubMed PMID: 17921376.
4. Bandegan A, Courtney-Martin G, Rafii M, Pencharz PB, Lemon PWR. Indicator amino acid oxidation protein requirement estimate in endurance-trained men 24 h postexercise exceeds both the EAR and current athlete guidelines. Am J Physiol Endocrinol Metab. 2019 May 1;316(5):E741-E748. doi: 10.1152/ajpendo.00174.2018. Epub 2019 Feb 19. PubMed PMID: 30779631.
5. Bandegan A, Courtney-Martin G, Rafii M, Pencharz PB, Lemon PW. Indicator Amino Acid-Derived Estimate of Dietary Protein Requirement for Male Bodybuilders on a Nontraining Day Is Several-Fold Greater than the Current Recommended Dietary Allowance. J Nutr. 2017 May;147(5):850-857. doi: 10.3945/jn.116.236331. Epub 2017 Feb 8. PubMed PMID: 28179492.
6. Wooding DJ, Packer JE, Kato H, West DWD, Courtney-Martin G, Pencharz PB, Moore DR. Increased Protein Requirements in Female Athletes after Variable-Intensity Exercise. Med Sci Sports Exerc. 2017 Nov;49(11):2297-2304. doi: 10.1249/MSS.0000000000001366. PubMed PMID: 28692631.
7. Helms, E.R., Aragon, A.A. & Fitschen, P.J. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr 11, 20 (2014) doi:10.1186/1550-2783-11-20
8. Aragon, A.A., Schoenfeld, B.J., Wildman, R. et al. International society of sports nutrition position stand: diets and body composition. J Int Soc Sports Nutr 14, 16 (2017) doi:10.1186/s12970-017-0174-y