Effect of soy protein isolate supplementation on the estradiol biosynthesis pathway in a female rat model

Abstract

Background Soy protein isolate (SPI) has gained popularity as an alternative to animal proteins. Soy consumption may have a link to rising serum estrogen in humans. This concern is attributed to phytoestrogens, specifically isoflavones present in soy protein, acting as estrogen substitutes and modulators. Objective The objective of this research was to assess the influence of SPI supplementation on estradiol hormone levels and the expression of genes associated with estrogen synthesis in female rats. Materials and methods Female Wistar rats (n=18) were evenly divided into three groups: group 1 (normal control) received oral administration of a saline vehicle. Group 2 (low dose) received 450 mg/kg body weight of SPI for 30 days. Group 3 (high dose) received 900 mg/kg body weight of SPI for 30 days. All administrations were conducted intragastrically. Results and conclusion The results of our study indicate that there was a significant increase in the levels of estradiol hormone in groups receiving low and high doses of SPI when compared with the control group. There was an upregulation in the messenger ribonucleic acid expression of the Cyp19 gene in low-dose and high-dose groups. Moreover, the low-dose group showed upregulation in the expression of the HSD3B gene. These genes are involved in the biosynthesis pathway of estrogen hormone in females. Therefore, the use of SPI should be cautious because it contains phytoestrogens (isoflavones), which have structural similarities to endogenous female estrogen and may cause hormonal disturbance in females.