Pet Food Ingredients
on August 23, 2007

Vitamin K3: is it unnecessary and toxic?

Supplementation with vitamin K3 doesn't appear to be a smoking gun

Vitamin K is one of those nutrients that we learn of early in nutrition training as an essential fat soluble vitamin that is important in clotting. Beyond that, we seldom discuss it Recently, however, there has been a concerted effort by a few "pet enthusiasts" to spook petfood manufacturers and well-meaning pet owners into the notion that vitamin K supplementation in the diet, specifically with vitamin K3 (menadione), is unnecessary and potentially toxic to pets. Determining whether they have a valid point warrants a bit of investigation.


Vitamin K is known principally for its role in blood clotting, but has also been reported to be involved with osteocalcin and bone formation, along with a number of other biomedical functions. By definition, vitamin K is any of several compounds that are based on 2-methyl-1,4-napthoquinone (also known as menadione) that express anti-hemorrhagic properties (Suttie, 2007). The amount of vitamin K recommended for dogs and cats is approximately 1 part per million of the diet (NRC, 2006).

Vitamin K can be supplied to the animal from a combination of sources: vitamins K1, K2 and K3. Vitamin K1, also known as phylloquionone, is found in green leafy vegetables and vegetable oils. Vitamin K2 is produced by gut bacteria and vitamin K3 is chemically synthesized. Vitamins K1 and K2 are "active" upon absorption. However, vitamin K3 must be "alkylated" by gut bacteria or tissue enzymes to become active This activation involves the addition of isoprenoid side chains, and in some literature this activated…

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