Why menadione sodium bisulfite complex remains a pet food puzzle

Menadione sodium bisulfite complex, or MSBC, is back in focus after a Truth about Pet Food report questioned why the ingredient appears in many pet foods even though its formal regulatory footing has long been murky. The core issue is that FDA says menadione and MSBC are “prior sanctioned” for poultry feed, while AAFCO and industry documents acknowledge the ingredient has also been used in pet foods for decades. In 2021, an AAFCO-convened expert panel concluded MSBC could be used as a safe and suitable source of vitamin K activity for all animal species, and AAFCO later published a guidance document reflecting that recommendation. The AAFCO Official Publication also lists “menadione sodium bisulfite complex” in its vitamin nomenclature table for finished dog and cat foods, but that table itself says formulators still need to confirm an ingredient definition supports the intended use. (fda.gov)

Why it matters: For veterinary professionals, this is less about a new safety signal and more about a long-running gap between ingredient practice and clean regulatory language. MSBC matters most in formulations where vitamin K supplementation is considered necessary, including fish-based cat foods, because AAFCO nutrient profiles call for vitamin K in cat diets containing more than 25% fish on a dry matter basis. The current debate may shape how clinicians answer pet parent questions about ingredient safety, label transparency, and whether a legally marketable ingredient is also clearly authorized for the species in question. (petfoodindustry.com)

What to watch: Watch for any future AAFCO action to create or revise a formal ingredient definition for pet food use, which would resolve the technical ambiguity more cleanly than guidance alone. (petfoodindustry.com)