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Infant feeding with soy formula milk: effects on puberty progression, reproductive function and testicular cell
Karen A L Tan1, Marion Walker, Keith Morris
1MRC Human Reproductive Sciences Unit, Centre for Reproductive Biology and Division of Reproductive and Developmental Science, The Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK.
Insights
Soy formula milk (SFM) did not cause adverse reproductive effects in male marmosets. However, SFM altered testis size and cell composition, suggesting potential compensated Leydig cell issues.
Area of Science:
- Reproductive biology
- Endocrinology
- Developmental toxicology
Background:
- Concerns exist regarding the reproductive health of male infants fed soy formula milk (SFM).
- Marmosets serve as a relevant non-human primate model for studying infant development and reproductive outcomes.
Purpose of the Study:
- To investigate the long-term reproductive effects of infant soy formula milk (SFM) feeding in male marmosets.
- To assess the impact of SFM on reproductive organ development, hormonal profiles, and fertility.
Main Methods:
- Male marmoset co-twins were fed either standard formula milk (SMA) or SFM from early infancy.
- Hormonal levels (testosterone) were monitored, and reproductive organs were weighed and analyzed histologically at maturity.
- Fertility was assessed in adulthood.
Main Results:
- Both SFM and SMA groups exhibited normal growth and pubertal development.
- Testis weight and the number of Sertoli and Leydig cells per testis were significantly increased in SFM-fed males.
- Fertility rates were comparable between SFM-fed (6/7) and SMA-fed (all) males, with no gross adverse effects observed.
Conclusions:
- Infant SFM feeding in male marmosets does not lead to overt adverse reproductive outcomes.
- SFM consumption alters testicular cell composition and size, with potential implications for Leydig cell function.
- Findings suggest that while SFM may not cause gross infertility, subtle reproductive alterations could occur, warranting further investigation in humans.
Background:
This marmoset study addresses concerns about feeding human male infants with soy formula milk (SFM).
Methods:
From age 4 to 5 days, seven male co-twin sets were fed standard formula milk (SMA) or SFM for 5-6 weeks; blood samples were subsequently collected at 10-week intervals. Testes from co-twins killed at 120-138 weeks were fixed for cell counts.
Results:
SFM- and SMA-fed twins showed normal weight gain; puberty started and progressed normally, based on blood testosterone measurements. Body weight, organ weights (prostate, seminal vesicles, pituitary, thymus and spleen) and penis length were comparable in co-twins. All SMA- and 6/7 SFM-fed males were fertile. Unexpectedly, testis weight (P = 0.041), Sertoli (P = 0.025) and Leydig cell (P = 0.026) numbers per testis were consistently increased in SFM-fed co-twins; the increase in Leydig cell numbers was most marked in males with consistently low-normal testosterone levels. Seminiferous epithelium volume per tubule showed a less consistent, non-significant increase in SFM-fed males; raised germ cell numbers per testis, probably due to increased Sertoli cells, conceivably resulted in larger testes. Average lumen size, although greater in SFM-fed group, was inconsistent between co-twins and the difference was not significant.
Conclusions:
Infant feeding with SFM has no gross adverse reproductive effects in male marmosets, though it alters testis size and cell composition, and there is consistent, if indirect, evidence for possible 'compensated Leydig cell failure'. Similar and perhaps larger changes likely occur in adult men who were fed SFM as infants.
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