Soy protein supplementation increases serum insulin-like growth factor-I in young and old men but does not affect markers of bone metabolism

J Nutr. 2002 Sep;132(9):2605-8. doi: 10.1093/jn/132.9.2605.


Recent studies suggest that soy protein (SP) protects bone in women; however, its effects on bone metabolism in men have not been investigated. Healthy men (59.2 +/- 17.6 y) were assigned to consume 40 g of either SP or milk-based protein (MP) daily for 3 mo in a double-blind, randomized, controlled, parallel design. Serum insulin-like growth factor-I (IGF-I), which is associated with higher rates of bone formation, was greater (P < 0.01) in men supplemented with SP than in those consuming MP. Serum alkaline phosphatase and bone-specific alkaline phosphatase activities, markers of bone formation, and urinary deoxypyridinoline excretion, a specific marker of bone resorption, were not different between the SP and MP groups. Furthermore, because substantial reductions in bone density occur in men at approximately 65 y of age, data were analyzed separately for men >/=65 y and those <65 y of age. The response to protein supplementation was consistent in the two age groups. The effects of SP on serum IGF-I levels suggest that SP may positively influence bone in men. Longer-duration studies examining the effects of SP or its isoflavones on bone turnover and bone mineral density and content in men are warranted.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Aging / metabolism*
  • Alkaline Phosphatase / blood
  • Alkaline Phosphatase / metabolism
  • Amino Acids / urine
  • Biomarkers / blood
  • Biomarkers / urine
  • Bone Density / drug effects
  • Bone Resorption / diagnosis
  • Bone Resorption / urine
  • Bone and Bones / metabolism*
  • Diet / standards
  • Dietary Supplements*
  • Double-Blind Method
  • Humans
  • Insulin-Like Growth Factor I / metabolism*
  • Male
  • Middle Aged
  • Milk Proteins / administration & dosage
  • Osteoporosis / prevention & control
  • Soybean Proteins / administration & dosage*
  • Soybean Proteins / pharmacology


  • Amino Acids
  • Biomarkers
  • Milk Proteins
  • Soybean Proteins
  • Insulin-Like Growth Factor I
  • deoxypyridinoline
  • Alkaline Phosphatase