title: The effects of soy and whey protein supplementation on acute hormonal reponses to resistance exercise in men.
abstract: OBJECTIVE
  For many resistance-trained men concerns exist regarding the production of estrogen with the consumption of soy protein when training for muscle strength and size. Thus, the purpose of this investigation was to examine the effects of soy and whey protein supplementation on sex hormones following an acute bout of heavy resistance exercise in resistance trained men.
  
  
  METHODS
  Ten resistance-trained men (age 21.7 ± 2.8 [SD] years; height 175.0 ± 5.4 cm; weight 84.2 ± 9.1 kg) volunteered to participate in an investigation. Utilizing a within subject randomized crossover balanced placebo design, all subjects completed 3 experimental treatment conditions supplementing with whey protein isolate (WPI), soy protein isolate (SPI), and maltodextrin placebo control for 14 days with participants ingesting 20 g of their assigned supplement each morning at approximately the same time each day. Following supplementation, subjects performed an acute heavy resistance exercise test consisting of 6 sets of 10 repetitions in the squat exercise at 80% of the subject's one repetition maximum.
  
  
  RESULTS
  This investigation observed lower testosterone responses following supplementation with soy protein in addition to a positive blunted cortisol response with the use of whey protein at some recovery time points. Although sex hormone binding globulin (SHBG) was proposed as a possible mechanism for understanding changes in androgen content, SHBG did not differ between experimental treatments. Importantly, there were no significant differences between groups in changes in estradiol concentrations.
  
  
  CONCLUSIONS
  Our main findings demonstrate that 14 days of supplementation with soy protein does appear to partially blunt serum testosterone. In addition, whey influences the response of cortisol following an acute bout of resistance exercise by blunting its increase during recovery. Protein supplementation alters the physiological responses to a commonly used exercise modality with some differences due to the type of protein utilized.
authors.affiliation: Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA. William.Kraemer@uconn.edu
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: Glenn
authors.initials: G
authors.lastname: Solomon-Hill
authors.forename: Brittanie M
authors.initials: BM
authors.lastname: Volk
authors.forename: Brian R
authors.initials: BR
authors.lastname: Kupchak
authors.forename: David P
authors.initials: DP
authors.lastname: Looney
authors.forename: Courtenay
authors.initials: C
authors.lastname: Dunn-Lewis
authors.forename: Brett A
authors.initials: BA
authors.lastname: Comstock
authors.forename: Tunde K
authors.initials: TK
authors.lastname: Szivak
authors.forename: David R
authors.initials: DR
authors.lastname: Hooper
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Flanagan
authors.forename: Carl M
authors.initials: CM
authors.lastname: Maresh
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Volek
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004044:Dietary Proteins / Q000494:pharmacology; D019587:Dietary Supplements; D004958:Estradiol / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D008894:Milk Proteins / Q000494:pharmacology*; D011134:Polysaccharides / Q000494:pharmacology; D055070:Resistance Training; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D030262:Soybean Proteins / Q000494:pharmacology*; D013025:Glycine max / Q000737:chemistry; D013739:Testosterone / Q000097:blood*; D000067816:Whey Proteins; D055815:Young Adult
chemical_list: D004044:Dietary Proteins; D008894:Milk Proteins; D011134:Polysaccharides; D012738:Sex Hormone-Binding Globulin; D030262:Soybean Proteins; D000067816:Whey Proteins; D013739:Testosterone; D004958:Estradiol; C008315:maltodextrin; D006854:Hydrocortisone