title: Muscle strength gains during resistance exercise training are attenuated with soy compared with dairy or usual protein intake in older adults: A randomized controlled trial.
abstract: OBJECTIVE
  Maintenance of muscle mass and strength into older age is critical to maintain health. The aim was to determine whether increased dairy or soy protein intake combined with resistance training enhanced strength gains in older adults.
  
  
  METHODS
  179 healthy older adults (age 61.5 ± 7.4 yrs, BMI 27.6 ± 3.6 kg/m(2)) performed resistance training three times per week for 12 weeks and were randomized to one of three eucaloric dietary treatments which delivered >20 g of protein at each main meal or immediately after resistance training: high dairy protein (HP-D, >1.2 g of protein/kg body weight/d; ∼27 g/d dairy protein); high soy protein (HP-S, >1.2 g of protein/kg body weight/d; ∼27 g/d soy protein); usual protein intake (UP, <1.2 g of protein/kg body weight/d). Muscle strength, body composition, physical function and quality of life were assessed at baseline and 12 weeks. Treatments effects were analyzed using two-way ANOVA.
  
  
  RESULTS
  83 participants completed the intervention per protocol (HP-D = 34, HP-S = 26, UP = 23). Protein intake was higher in HP-D and HP-S compared with UP (HP-D 1.41 ± 0.14 g/kg/d, HP-S 1.42 ± 0.61 g/kg/d, UP 1.10 ± 0.10 g/kg/d; P < 0.001 treatment effect). Strength increased less in HP-S compared with HP-D and UP (HP-D 92.1 ± 40.8%, HP-S 63.0 ± 23.8%,UP 92.3 ± 35.4%; P = 0.002 treatment effect). Lean mass, physical function and mental health scores increased and fat mass decreased (P ≤ 0.006), with no treatment effect (P > 0.06).
  
  
  CONCLUSIONS
  Increased soy protein intake attenuated gains in muscle strength during resistance training in older adults compared with increased intake of dairy protein or usual protein intake.
  
  
  BACKGROUND
  ACTRN12612000177853 www.anzctr.org.au.
authors.affiliation: Alliance for Research in Exercise, Nutrition and Activity (ARENA), Sansom Institute for Health Research, University of South Australia, Adelaide, South Australia, Australia.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Thomson
authors.affiliation: Commonwealth Scientific and Industrial Research Organisation - Food and Nutrition Flagship, Adelaide, South Australia, Australia.
authors.forename: Grant D
authors.initials: GD
authors.lastname: Brinkworth
authors.affiliation: Commonwealth Scientific and Industrial Research Organisation - Food and Nutrition Flagship, Adelaide, South Australia, Australia.
authors.forename: Manny
authors.initials: M
authors.lastname: Noakes
authors.affiliation: Alliance for Research in Exercise, Nutrition and Activity (ARENA), Sansom Institute for Health Research, University of South Australia, Adelaide, South Australia, Australia. Electronic address: jon.buckley@unisa.edu.au.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Buckley
mesh_terms: D000368:Aged; D001823:Body Composition; D015992:Body Mass Index; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D005260:Female; D005500:Follow-Up Studies; D018737:Hand Strength; D006801:Humans; D008297:Male; D062407:Meals; D008875:Middle Aged; D008894:Milk Proteins / Q000008:administration & dosage*; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology; D011788:Quality of Life; D055070:Resistance Training; D030262:Soybean Proteins / Q000008:administration & dosage*; D016896:Treatment Outcome; D055105:Waist Circumference
chemical_list: D004044:Dietary Proteins; D008894:Milk Proteins; D030262:Soybean Proteins
keywords: Dairy; Older adults; Protein; Resistance training; Soy; Strength