LLLI Center for Breastfeeding Information

Journal Abstract of the Month for February 2003

Editorial comment on:
"Infant feeding with soy formula milk: Effects on the testis and on blood testosterone levels in marmoset monkeys during the period of neonatal testicular activity." by Richard M. Sharpe et al. Ob Gyn Survey 2003-2;58(2):120-22
Original paper published in Hum Reprod 2002;17:1692-1703

Infants not breastfed are often fed powdered milk formula derived from soybean extracts, often used in the first months of life. Animal studies have been done due to concerns on the high amount of isoflavenoid phytoestrogens in soy products. Plant derived products such as soy may be "natural" but may not be innocuous.

In tests done on Marmoset monkeys twins, animals received either standard cow milk formula or soy milk formula after the first 4-5 days of life. Significant differences were found between the two groups. Leydig cells were increased by almost 75% and the SFM-fed monkeys had a suppression of the testosterone surge.

The authors feel that feeding human infants a soy product in the early months of life can affect plasma testosterone levels and testosterone-dependent tissues in ways that are not yet clear. They concluded that it would be wise to avoid feeding soy products to infants when alternatives are available.

This article will be categorized in the following subjects:
Soy Formula, Formula Concerns, Sexuality, Other Species