Everyone knows protein-intake is an important component in the development of lean muscle. Many times individuals (particularly those trying to bulk-up or body-build) find themselves undergoing diets that contain upwards of 1.5-2 or even more grams of protein per pound of bodyweight each day. Below are abstracts from both a study on protein intake and position statement from the International Society of Sports Nutrition addressing protein intake among athletes and those looking to improve their body composition.

Effect of Protein Intake on Strength, Body Composition and Endocrine Changes in Strength/Power Athletes
Jay R Hoffman,corresponding author1 Nicholas A Ratamess,1 Jie Kang,1 Michael J Falvo,1 and Avery D Faigenbaum1

Abstract

Comparison of protein intakes on strength, body composition and hormonal changes were examined in 23 experienced collegiate strength/power athletes participating in a 12-week resistance training program. Subjects were stratified into three groups depending upon their daily consumption of protein; below recommended levels (BL; 1.0 – 1.4 g/kg/day; n = 8), recommended levels (RL; 1.6 – 1.8 g/kg/day; n = 7) and above recommended levels (AL; > 2.0 g/kg/day; n = 8). Subjects were assessed for strength [one-repetition maximum (1-RM) bench press and squat] and body composition. Resting blood samples were analyzed for total testosterone, cortisol, growth hormone, and insulin-like growth factor. No differences were seen in energy intake (3,171 +/- 577 kcal) between the groups, and the energy intake for all groups were also below the recommended levels for strength/power athletes. No significant changes were seen in body mass, lean body mass or fat mass in any group. Significant improvements in 1-RM bench press and 1-RM squat were seen in all three groups, however no differences between the groups were observed. Subjects in AL experienced a 22% and 42% greater change in Δ 1-RM squat and Δ 1-RM bench press than subjects in RL, however these differences were not significant. No significant changes were seen in any of the resting hormonal concentrations. The results of this study do not provide support for protein intakes greater than recommended levels in collegiate strength/power athletes for body composition improvements, or alterations in resting hormonal concentrations.

Source:PubMed

International Society of Sports Nutrition position stand: protein and exercise

Bill Campbell,1 Richard B Kreider,corresponding author2 Tim Ziegenfuss,3 Paul La Bounty,4 Mike Roberts,5 Darren Burke,6 Jamie Landis,7 Hector Lopez,8 and Jose Antonio9

Abstract

Position Statement
The following seven points related to the intake of protein for healthy, exercising individuals constitute the position stand of the Society. They have been approved by the Research Committee of the Society. 1) Vast research supports the contention that individuals engaged in regular exercise training require more dietary protein than sedentary individuals. 2) Protein intakes of 1.4 – 2.0 g/kg/day for physically active individuals is not only safe, but may improve the training adaptations to exercise training. 3) When part of a balanced, nutrient-dense diet, protein intakes at this level are not detrimental to kidney function or bone metabolism in healthy, active persons. 4) While it is possible for physically active individuals to obtain their daily protein requirements through a varied, regular diet, supplemental protein in various forms are a practical way of ensuring adequate and quality protein intake for athletes. 5) Different types and quality of protein can affect amino acid bioavailability following protein supplementation. The superiority of one protein type over another in terms of optimizing recovery and/or training adaptations remains to be convincingly demonstrated. 6) Appropriately timed protein intake is an important component of an overall exercise training program, essential for proper recovery, immune function, and the growth and maintenance of lean body mass. 7) Under certain circumstances, specific amino acid supplements, such as branched-chain amino acids (BCAA’s), may improve exercise performance and recovery from exercise.

Source:PubMed

A lot of good information can be drawn from these abstracts, particularly the suggestion that a protein intake greater than 2.0g/kg/day seems to not have any beneficial impact one’s body composition or resting hormonal concentrations when compared to intakes of 1.4-2.0g/kg/day.