title: The impact of varying dietary protein on serum IGF-I, IGFBP-1, and IGFBP-3 during 6 days of physical activity.
abstract: This study was designed to investigate the impact of dietary protein intake on serum concentrations of IGF-I and IGFBP-1 and relative amounts of serum IGFBP-3 during 6 d of physical activity. Ten men (23.8 +/- 2.0 y of age) were assigned to 1 of 3 trials in a random crossover design. Each trial was isocaloric but with varying amounts of dietary protein: 50 g, 100 g, or 200 g. Subjects expended 500 kcal through treadmill running or weightlifting on alternate days for 6 d. Fasting blood samples were obtained for measurement of IGF-I, IGFBP-1, and IGFBP-3. Pre-post 24-h urine was measured for urea nitrogen. 50 g/d of protein resulted in a negative nitrogen balance, whereas 100 g/d and 200 g/d resulted in a positive nitrogen balance--200 g greater (P < 0.05) than 50 g and 100 g. Baseline IGF-I, BP-1, and BP-3 were not different among treatments. IGF-I decreased (P = 0.002) during the 6 d. Postintervention IGFBP-I was greater (P = 0.03) than at baseline. Postintervention IGFBP-3 values were not different from baseline or between trials. A 6-d modification of protein intake, while in energy balance, during a strength and conditioning program does not appear to modify serum concentrations of IGF-I or IGFBP-1 or relative amounts of IGFBP-3.
authors.affiliation: Human Performance Laboratory, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ormsbee
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Clapper
authors.forename: Joan L
authors.initials: JL
authors.lastname: Clapper
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Vukovich
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015444:Exercise / Q000502:physiology*; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D009584:Nitrogen / Q000652:urine
chemical_list: D004044:Dietary Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I; D009584:Nitrogen