Plasma insulin-like growth factor I levels in rats are reduced by dietary supplementation of flaxseed or its lignan secoisolariciresinol diglycoside

Flaxseed and its lignan secoisolariciresinol diglycoside (SDG) inhibit mamm ary tumor development in rats. Increased plasma insulin-like growth factor I(IGF-I) concentrations are associated with increased breast cancer risk. T herefore, the effect of flaxseed 15%) or SDG (1.5 mg/day) supplementation o n plasma IGF-I levels was examined in rats treated with or without N-methyl -N-nitrosourea (MNU), In MNU-free rats. flaxseed and SDG reduced plasma IGF -I levels, which were inversely related to urinary lignan excretion. Only f laxseed significantly reduced plasma IGF-I concentrations in MNU-treated ra ts. The anticancer effect of ftaxseed and SDG may be related, in part. to r eductions in plasma IGF-I. (C) 2000 Elsevier Science Ireland Ltd. All right s reserved.