Animal & Veterinary
UPDATE ON HUMAN FOOD SAFETY OF BST
FDA Veterinarian Newsletter March/April 1999 Volume XIV, No II
FDA's Center for Veterinary Medicine (CVM) has reexamined the human food safety of recombinant bovine somatotropin (rbST) in response to recent inquiries about the safety of this product. FDA's CVM approved Monsanto Company's rbST product, Posilac® in November 1993 after a comprehensive review of the product's safety and efficacy, including human food safety. CVM has issued a detailed report based on a careful audit of the human food safety sections of this approval. CVM's finding upholds the Agency's original conclusion that milk from cows treated with rbST is safe for human consumption.
The new concerns about the safety of Posilac® , currently the only rbST product approved for increasing milk production in dairy cattle in the U.S., were stimulated by the product's review for approval in Canada. In April 1998, while the review process was underway, the Health Protection Branch (HPB) of Health Canada prepared an internal memorandum, entitled "rBST (Nutrilac) 'GAPS Analysis' Report," which was critical of the review method used by the HPB, and identified areas of human food safety concern.
In particular, the Canadian report claimed that a 90-day oral toxicity study in rats had been "misreported" by FDA, and cited allegations of significant absorption of oral rbST based on serum antibody levels in the rats, and toxicity to the rats. Both the memorandum and the circumstances under which it was made public became highly controversial in Canada.
Following the publication of the Canadian document several groups and individuals in the United States raised questions about the safety of milk from rbST-treated cows. In response to these concerns, CVM prepared a "Report on the Food and Drug Administration's Review of the Safety of Recombinant Bovine Somatotropin." The Report affirmed the original review of the 90-day rat oral toxicity study, which concluded that there were no biologically significant observed effects in either the thyroid or the prostate.
In addition, CVM conducted a review of the report cited by Health Canada of the antibody response to oral rbST. While CVM concurred that oral exposure to high doses of rbST results in antibody production, there is no evidence for biologically significant absorption of intact rbST from the gastrointestinal tract.
The "Report on the Food and Drug Administration's Review of the Safety of Recombinant Bovine Somatotropin" is available on the CVM's Internet Home Page.
A copy of this report may also be obtained by calling or writing the FDA Veterinarian.