title: Effects of dietary soy protein on skeletal muscle volume and strength in humans with various physical activities.
abstract: BACKGROUND
  In recent years, the number of bedridden people is rapidly increasing due to aging or lack of exercise in Japan. This problem is becoming more serious, since there is no countermeasure against it. In the present study, we designed to investigate whether dietary proteins, especially soy, had beneficial effects on skeletal muscle in 59 volunteers with various physical activities.
  
  
  METHODS
  We subjected 59 volunteers with various physical activities to meal intervention examination. Persons with low and high physical activities were divided into two dietary groups, the casein diet group and the soy diet group. They ate daily meals supplemented with 7.8 g of powdered casein or soy protein isolate every day for 30 days. Bedridden patients in hospitals were further divided into three dietary groups: the no supplementation diet group, the casein diet group and the soy diet group. They were also subjected to a blood test, a urinalysis, magnetic resonance imaging analysis and muscle strength test of the knee before and after the meal intervention study.
  
  
  RESULTS
  Thirty-day soy protein supplementation significantly increased skeletal muscle volume in participants with low physical activity, compared with 30-day casein protein supplementation. Both casein and soy protein supplementation increased the volume of quadriceps femoris muscle in bedridden patients. Consistently, soy protein significantly increased their extension power of the knee, compared with casein protein. Although casein protein increased skeletal muscle volume more than soy protein in bedridden patients, their muscle strength changes by soy protein supplementation were bigger than those by casein protein supplementation.
  
  
  CONCLUSIONS
  The supplementation of soy protein would be one of the effective foods which prevent the skeletal muscle atrophy caused by immobilization or unloading.
authors.affiliation: Department of Nutritional Physiology, Institute of Health Biosciences, the University of Tokushima.
authors.forename: Rie
authors.initials: R
authors.lastname: Hashimoto
authors.forename: Atsuko
authors.initials: A
authors.lastname: Sakai
authors.forename: Masumi
authors.initials: M
authors.lastname: Murayama
authors.forename: Arisa
authors.initials: A
authors.lastname: Ochi
authors.forename: Tomoki
authors.initials: T
authors.lastname: Abe
authors.forename: Katsuya
authors.initials: K
authors.lastname: Hirasaka
authors.forename: Ayako
authors.initials: A
authors.lastname: Ohno
authors.forename: Shigetada
authors.initials: S
authors.lastname: Teshima-Kondo
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Yanagawa
authors.forename: Natsuo
authors.initials: N
authors.lastname: Yasui
authors.forename: Mikiko
authors.initials: M
authors.lastname: Inatsugi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Doi
authors.forename: Masanori
authors.initials: M
authors.lastname: Takeda
authors.forename: Rie
authors.initials: R
authors.lastname: Mukai
authors.forename: Junji
authors.initials: J
authors.lastname: Terao
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nikawa
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000652:urine; D004044:Dietary Proteins / Q000008:administration & dosage*; D015444:Exercise; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D030262:Soybean Proteins / Q000008:administration & dosage*
chemical_list: D004044:Dietary Proteins; D030262:Soybean Proteins; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine