Soy protein formulas in children: no hormonal effects in long-term feeding.

Recently, the finding of high plasma concentration of phyto-oestrogens in soy protein formula (SPF) fed children has focused scientific attention on the phyto-oestrogens (isoflavones genistein, daidzein, and their glycosides) contained in SPFs. The aim of this study was to evaluate some hormonal and metabolic effects of long-term (more than 6 months) SPF feeding. We enrolled 48 children, mean age 37 months (range 7-96 months), 27 males and 21 females. All children underwent physical examination. Bone age, urinary markers of bone metabolism, serum levels of bone alkaline phosphatase, osteocalcin, 17beta-oestradiol, and intact parathyroid hormone were measured. Eighteen healthy children represented the control group. No abnormalities were observed in auxological parameters; none of the enrolled girls showed signs/symptoms of precocious puberty and none of the boys presented gynecomastia; bone age was within the normal range. The serum level of bone alkaline phosphatase, osteocalcin, 17beta-oestradiol, and intact parathyroid hormone, and the urinary levels of the markers of bone metabolism were all within normal values. We conclude that long-term feeding with SPFs in early life does not seem to produce oestrogen-like hormonal effects.