Zeranol (α-zearalanol) is a non-steroidal estrogen agonist. It is a mycotoxin, derived from fungi in the Fusarium family, and may be found as a contaminant in fungus-infected crops. It is 3-4x more potent as an estrogen agonist than the related compound zearalenone.

 

Zeranol is approved for use as a growth promoter in livestock, including beef cattle, in the United States. In Canada, it is approved for use in beef cattle only. Its application is not approved for use in the European Union.

 

Zeranol increases cancer cell proliferation in already existing breast cancer. There are mixed results to whether zeranol has anticancer or carcinogenic properties in non cancer containing breast cells depending on dose.[3] Overall evidence points to zeranol being a risk factor and promoter for cancer.[3] However, dietary exposure from the use of zeranol-containing implants in cattle is insignificant.