Does soy protein affect circulating levels of unbound IGF-1?

Mark Messina, PJ Magee

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Introduction Despite the enormous amount of research that has been conducted on the role of soyfoods in the prevention and treatment of chronic disease, the mechanisms by which soy exerts its physiological effects are not fully understood. The clinical data show that neither soyfoods nor soy protein nor isoflavones affect circulating levels of reproductive hormones in men or women. However, some research suggests that soy protein, but not isoflavones, affects insulin-like growth factor I (IGF-1). Methods Since IGF-1 may have wide-ranging physiological effects, we sought to determine the effect of soy protein on IGF-1 and its major binding protein insulin-like growth factor-binding protein (IGFBP-3). Six clinical studies were identified that compared soy protein with a control protein, albeit only two studies measured IGFBP-3 in addition to IGF-1. Results Although the data are difficult to interpret because of the different experimental designs employed, there is some evidence that large amounts of soy protein (>25 g/day) modestly increase IGF-1 levels above levels observed with the control protein. Conclusion The clinical data suggest that a decision to incorporate soy into the diet should not be based on its possible effects on IGF-1.
Original languageEnglish
JournalEuropean Journal of Nutrition
Early online date22 Apr 2017
Publication statusPublished online - 22 Apr 2017


  • soy
  • isoflavones
  • clinical trials
  • cancer


Dive into the research topics of 'Does soy protein affect circulating levels of unbound IGF-1?'. Together they form a unique fingerprint.

Cite this