Although nitrogen balance and stable isotope studies are of great interest in building an experimental database to support, refute, or challenge official published levels of requirements, from a practical standpoint, coaches, athletes, and individuals involved in daily exercise regimens are not usually interested in the scientific debate over the issue of protein requirements. Performance is ultimately the only outcome that is important for athletes. Many authors have made this point, yet the studies that have attempted to investigate the influence of protein intake on performance have been scarce [10,11,16,18,51]. Millward  stated, ''Thus, the key test of adequacy of either protein or amino acid intake must be the long-term response in terms of the specific function of interest.'' This key test would vary for each type of exercise training performed, each sport, each position within a particular sport, and even among individuals participating in any given event or sharing a position (eg, an American football quarterback compared with a running back). Energy balance, intake of other nutrients, and individual genetic makeup all contribute to the response to training and nutrient intake, and the influence of the amount of protein ingested per day on performance for an athlete varies and often is difficult to determine.
There are ample limitations for determination of optimal protein intake by measurement of performance. These limitations have been articulated previously [11,13,16,18,51] and include difficulty, if not impossibility, in controlling innumerable physiologic variables (eg, training status, training details, energy balance, and standardization of life aspects such as sleep, work, and emotional upheavals) and inherent difficulty in defining the appropriate end points to be measured and the insensitivity of performance and end point measures [11,16,18,51].
Determination of appropriate protein intake to optimize performance, by any method, is limited by the definition of the population to be targeted. Generally, studies broadly divide athletes into strength or power athletes and endurance athletes. These broad distinctions may not be specific enough to provide appropriate protein intake information for many athletes. There have been attempts to categorize various athletic groups further. Tarnopolsky  considered that endurance athletes may be divided into three broad categories and estimated protein needs for these groups. Delineations such as these provide more information for practitioners, but as is pointed out in Tarnopol-sky's article, there are individuals who do not fit the broad categorizations. It seems clear that, at this juncture, there are ample gaps in knowledge that do not allow general recommendations that may be meaningful to all athletes. Football and rugby players incorporate a great deal of power and endurance training. A decathlete, by definition, participates in quite varied training. Gender is an important factor to consider [16,23,53], but few data exist on performance measures on different protein intakes for men and women. To recommend a specific number of grams of protein to all participants in a broad category of athletes seems nonsensical. Protein recommendations are best made based on the individual circumstances of each athlete.
Was this article helpful?