Effects of Soy-Based Infant Formula on Male Marmoset Twins

 

A study on male marmoset twins investigated the effects of soy-based infant formula (1.6–3.5 mg/kg/day) compared to milk during the critical developmental period from 4 to 45 days after birth. Key findings include:

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• No difference in testes weight between the soy-fed and milk-fed groups at the end of the study.

• Suppressed testosterone surge in soy-fed marmosets, indicating potential disruption in normal hormonal development.

• Reduced plasma testosterone levels in the soy-fed group.

• No consistent difference in Sertoli or germ cell numbers, which are crucial for sperm production.

• Increased Leydig cell numbers by 74% in the soy-fed group, suggesting a compensatory response to reduced testosterone levels.

 

These results highlight that while testicular size remained unchanged, soy-based formula altered hormonal regulation, particularly by suppressing early-life testosterone surges—a critical factor in male reproductive development. The increase in Leydig cells may reflect the body's attempt to counteract this hormonal imbalance.

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Citation: Committee on Toxicity. Phytoestrogens and health. Food standard agency (2003).