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.Necessity 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 form is called ...