Subchronic toxicity study on soy isoflavones in rats

Area of Science:

• Toxicology
• Endocrinology
• Nutritional Science

Background:

• Soy isoflavones (SIF) are widely consumed compounds with potential health benefits.
• However, their effects on male reproductive health require thorough toxicological investigation.
• Understanding the subchronic toxicity of SIF is crucial for assessing their safety.

Purpose of the Study:

• To investigate the subchronic toxicity of soy isoflavones (SIF) in male rats.
• To determine the no observed adverse effect level (NOAEL) of SIF in this animal model.

Main Methods:

• Fifty Sprague-Dawley rats were administered SIF via gavage at doses of 0, 0.2, 0.5, 1.5, and 4.5 g/kg body weight for 13 weeks.
• Weekly monitoring of clinical signs, body weight, and food consumption was conducted.
• Comprehensive analyses included urinalysis, hematology, clinical chemistry, hormone level testing (total testosterone, FSH), and histopathology.

Main Results:

• No mortality or treatment-related clinical signs were observed.
• Significantly reduced body weight and food consumption were noted in the 1.5 and 4.5 g/kg bw groups.
• SIF treatment led to decreased triglyceride, increased HDL cholesterol, and significantly lower total testosterone levels in a dose-dependent manner.
• Mammary gland hyperplasia and latex excretion were observed in the highest dose group (4.5 g/kg bw).

Conclusions:

• High-dose soy isoflavones (SIF) induce significant endocrine disruption in male rats.
• The no observed adverse effect level (NOAEL) for SIF in male rats was established at 0.20 g/kg bw.
• These findings highlight potential risks associated with high SIF consumption in males.