What was recalled
This page synthesizes the MK-7 systemic bone health evidence framework around commercial pet food vitamin K supplementation. Menaquinone-7 (MK-7) is one of several K2 menaquinone forms differentiated by isoprenoid side-chain length. The MK-4 / MK-7 distinction is the most pharmacologically consequential: MK-4 menaquinone has approximately 1-hour serum half-life and is produced both directly (bacterial synthesis, animal-tissue origin) and indirectly through in-vivo conversion from K1 phylloquinone and from K3 menadione absorbed from pet food supplementation; MK-7 menaquinone has approximately 3-day serum half-life and is produced primarily by Bacillus subtilis natto fermentation, the dominant commercial source for human supplementation. The 72-fold longer half-life of MK-7 versus MK-4 produces substantially higher and longer steady-state extrahepatic tissue concentrations from equivalent oral dose. The K1 / MK-4 / MK-7 source-form framework is covered separately on our vitamin K2 menaquinone controversy page; this page focuses specifically on the systemic bone health evidence base and the translation gap from human RCT to companion animal.
The human RCT evidence base for MK-7 systemic bone health expanded substantially between 2010 and 2024. The seminal Knapen 2013 randomized controlled trial enrolled 244 postmenopausal women in a 3-year double-blind placebo-controlled study of MK-7 supplementation at 180 µg/day. The trial documented statistically significant improvement in lumbar spine and femoral neck bone mineral density relative to placebo, plus improvement in carboxylation status of osteocalcin (the bone Gla protein) measured by carboxylated:undercarboxylated osteocalcin ratio. Subsequent meta-analyses have supported the bone mineral density signal for MK-7 at 180 µg/day or higher; lower doses and short durations show inconsistent results. The Rotterdam Study cohort analysis documented inverse association between dietary MK-7 intake and incident cardiovascular calcification, cardiovascular mortality, and all-cause mortality, providing observational support alongside the bone RCT evidence for extrahepatic K2 sufficiency.
The companion-animal evidence base for MK-7 supplementation is essentially absent. Controlled trials of direct MK-7 supplementation in dogs and cats with outcome measures of bone mineral density, vascular calcification, or osteocalcin carboxylation status have not been published in peer-reviewed veterinary nutrition literature at scale. The mechanistic rationale (gamma-glutamyl carboxylase substrate preference, extrahepatic Gla-protein activation) transfers across mammalian species, but the dose-response relationship, optimal supplementation timing, target outcome populations (senior orthopedic, chronic kidney disease with vascular calcification, large-breed orthopedic development), and safety profile in dogs and cats have not been characterized through controlled trial design. Pet food brands marketing K2 menaquinone inclusion are operating ahead of companion-animal-specific evidence.
Why it was recalled
The structural concerns have three layers. Layer one — menadione metabolism produces MK-4 distribution, not MK-7 distribution: the dominant pet food vitamin K supplementation strategy uses K3 menadione (menadione sodium bisulfite complex, menadione dimethylpyrimidinol bisulfite, menadione nicotinamide bisulfite). After intestinal absorption, the body alkylates menadione to MK-4 menaquinone in target tissues through the UbiA prenyltransferase domain-containing protein 1 (UBIAD1) enzyme. The conversion is metabolically active and produces functional MK-4 vitamin K activity, but the pharmacokinetic profile is the short-half-life MK-4 form — not the long-half-life MK-7 form. Pet food menadione supplementation therefore meets AAFCO vitamin K activity minimums and supports clotting-factor carboxylation adequately, but does not deliver the extrahepatic tissue exposure pattern that human MK-7 RCT evidence is built on.
Layer two — the extrahepatic Gla-protein activation framework is theoretically applicable but companion-animal trial evidence is absent: the human evidence for MK-7 systemic bone health rests on the premise that hepatic vitamin K activity (clotting-factor carboxylation) has higher priority than extrahepatic vitamin K activity (osteocalcin carboxylation in bone, matrix Gla protein carboxylation in vasculature) when total vitamin K availability is limited. An animal can have adequate clotting-factor activity (normal prothrombin time, normal activated partial thromboplastin time) while having suboptimal osteocalcin and matrix Gla protein carboxylation. Companion animals fed AAFCO-compliant menadione-supplemented diets are likely in a similar physiologic state to free-living adult humans on standard Western diets — adequate hepatic vitamin K function, partially undercarboxylated extrahepatic Gla proteins. Whether this translates to clinically meaningful bone or vascular benefit from direct MK-7 supplementation in dogs and cats requires controlled-trial data that has not been generated.
Layer three — senior orthopedic and chronic kidney disease use cases are the most plausible targets but remain speculative: the human MK-7 supplementation populations with the strongest evidence are postmenopausal women with osteoporosis risk (Knapen 2013 trial population) and adults with chronic kidney disease and elevated vascular calcification risk (multiple smaller trials). Translation to companion animals would target senior orthopedic dogs and cats (osteoarthritis with bone-density concerns, cancer cachexia with bone loss) and chronic kidney disease pets with documented vascular calcification on imaging. Veterinary nutraceutical formulations for senior orthopedic support occasionally include K2 menaquinones, but the dose-response relationship is extrapolated from human data and brand-level differentiation around K2 source form is rarely transparent.
Health risks for your pet
MK-7 menaquinone supplementation at typical human and veterinary nutraceutical doses (45-180 µg/day in humans, similar range scaled by body weight in pets) is generally well-tolerated. Documented safety concerns include warfarin and warfarin-derivative anticoagulant interaction — MK-7 supplementation antagonizes the anticoagulant effect of warfarin and similar vitamin-K-antagonist anticoagulants, and pets on these medications should not receive K2 supplementation without veterinary supervision and INR monitoring; theoretical accumulation concern at very high doses or prolonged supplementation has not been clinically documented but warrants conservative dosing; and quality control variability in commercial MK-7 supplements has been documented in human supplement testing, with some products containing substantially less MK-7 than label claim or containing MK-4 / MK-7 mixtures rather than pure MK-7.
The pet-food-specific concern is the marketing-evidence gap: brands marketing K2 menaquinone inclusion in commercial pet food or veterinary nutraceuticals are typically using MK-4 from menadione metabolism rather than direct MK-7 supplementation, and are operating ahead of companion-animal-specific controlled-trial evidence. Pet owners interpreting K2 marketing claims as supported by the same evidence base as human MK-7 RCTs are receiving an inaccurate representation of the companion-animal evidence base. The clinical risk is low (MK-7 is well-tolerated), but the consumer-disclosure framework around brand-level K2 source-form differentiation is weak across the category.
What to do if you bought affected product
Pet owners can navigate MK-7 pet food marketing claims appropriately through several practical approaches: (1) understand that pet food vitamin K supplementation is overwhelmingly menadione (K3) producing MK-4 distribution — not MK-7 distribution; if a brand markets "K2 menaquinone" inclusion without specifying MK-7 form, the form is most likely MK-4 from menadione metabolism or low-dose direct MK-4 supplementation; (2) request K source-form disclosure from brand customer service — brands using direct MK-7 supplementation typically promote the distinction prominently with the natto-fermentation source; (3) do not extrapolate human MK-7 RCT evidence directly to pet food marketing claims — the Knapen 2013 trial and Rotterdam Study evidence is high-quality for postmenopausal human bone mineral density and cardiovascular calcification, but companion-animal translation requires controlled-trial data that has not been generated; (4) for senior orthopedic dogs and cats or pets with chronic kidney disease and documented vascular calcification, discuss K2 supplementation with your veterinarian as evidence-informed empiricism rather than established indication; (5) watch for warfarin and anticoagulant rodenticide exposure contexts — pets on warfarin or recovering from anticoagulant rodenticide exposure should not receive K2 supplementation without veterinary supervision and coagulation monitoring; (6) treat MK-7 pet food marketing as a transparency signal rather than a clinical-outcome guarantee.
How this affects KibbleIQ’s grade
The KibbleIQ rubric v15 does not currently differentiate vitamin K source form per our published methodology, since brand-level disclosure of K1 / MK-4 / MK-7 / K3 menadione source form is rare and the companion-animal evidence base for direct MK-7 supplementation effect on bone and vasculature has not been generated. Future rubric extension under consideration: brands publishing K2 menaquinone source-form disclosure (particularly direct MK-7 inclusion above standard menadione) and inclusion-rate transparency would receive favorable scoring weight, with weighting calibrated to companion-animal evidence as it develops. The K1 / K2 / K3 source-form framework is covered in our vitamin K2 menaquinone controversy and vitamin K1 phylloquinone controversy pages. For now, our recommendation: treat MK-7 pet food marketing claims as transparency-quality signals rather than clinical-outcome guarantees, and reserve direct MK-7 supplementation discussion for senior orthopedic and chronic kidney disease contexts under veterinary guidance.