A randomized double blind-cross over trial of soya protein for the treatment of cyclical breast pain

Twenty patients with cyclical breast pain were enrolled in a double-blind c ross-over trial in which either a soy protein drink or a flavoured cow's mi lk was taken orally each day for 3 months before crossing over to the alter nate drink for a further 3 months. Records of pain scores were taken throug hout the study. Blood was also taken before and after 3 and 6 months for th e measurement of phytoestrogents to assess compliance. Two women withdrew f rom the study at the outset leaving 18 evaluable patients who completed the study. Of these 10 (56%) felt that soy protein improved breast pain (two o f whom received soy as first treatment) and two (11%) felt that cow's milk alleviated symptoms tone receiving this as first preparation) and the remai ning six (33%) experienced no relief of pain with either dietary preparatio n. Blood levels of diadzein and genistein were elevated after the ingestion of soy protein in only 13 patients (seven of whom felt that soy improved t heir breast pain); in the remaining five patients (three of whom suggested that soy protein improved breast pain) phytoestrogen levels were no higher than pretreatment values. Although the ingestion of soy protein may be asso ciated with relief of breast pain, these results illustrate the problem of non-specific effects in studies of mastalgia in that 1) cow's milk also rel ieved breast pain in some patients and 2) that the benefits of soy protein were not always associated with evidence of elevated circulating levels of phyto-estrogens, indicating the difficulty of compliance in dietary interve ntion studies using soy foods. (C) 2000 Harcourt Publisher Ltd.