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"The Thinking Person's Pet Food"™ – Since 1979

Vitamin K



Q: I have heard that vitamin K3 is toxic in pets. Is that what the menadione is in your foods?

A: Previously there has been a minute amount of K3 in the Wysong dry cat and dog diets (only).

As for the current rumor that K3 is toxic in pets, consider the following.

The National Research Council Committee on Dog and Cat Nutrition, which is composed of 10 experts in the field of dog and cat nutrition, has just recently (2006) released the new N.R.C. publication, "Nutrient Requirements of Dogs and Cats." The requirements and recommendations they give are in terms of menadione without any qualification as to source. If menadione (K3) was toxic to dogs or cats at the levels commonly used, these folks would most assuredly have addressed the situation in this publication.

Admittedly, the experts can be wrong. But in this case, with over a half century of use, and millions of animals fed K3 through generations with no reported toxicity at recommended inclusion rates, it is likely that they are not.

Additionally, common sense would indicate that, if the common vitamin K sources used in feeds for all kinds of animals, including birds, mammals and fish, were at all toxic, in any species, at the levels commonly used, the use of these vitamin K sources would have ceased very shortly after their introduction more than 50 years ago.

In the 1985 NRC "Nutrient Requirements of Dogs," the 6-member panel of experts on dog nutrition makes the following statement (page 27): "Although it is doubtful that supplemental vitamin K is necessary for the normal dog, it may be prudent to provide 22 micrograms of menadione (or vitamin K equivalent) per kilogram of body weight daily for adult maintenance and 44 micrograms per kilogram of body weight during growth. This would be more than supplied by a dry diet concentration of 1.0 mg of menadione per kilograms." This quote is also cited in the 2006 publication.

The toxicity reported in current urban legend is manifest as the formation of Heinz bodies in red blood cells and a dose of 2.5mg per pound of body weight per day was required in the diet to produce that effect. The amount used in Wysong foods was approximately 7,000 times less than that!

This consideration plus the fact that Wysong cat foods and dog foods have been fed to tens of thousands of pets through several generations over a period of 35 years with no toxic effects - only benefit - is reason for every confidence.

Please keep in mind that every ingredient in any pet or human food is potentially toxic at high enough levels. The dose makes the poison. Oxygen and water are essential to life but toxic at high enough dose.

Pet owners are wise to see the constant alarms about this or that ingredient in pet foods for what they are, marketing attempts (not well reasoned science or evidence) by companies trying to make demons out of competition.

Because heat extrusion can diminish the levels of many important nutrients in pet foods, we felt the benefits of small insurance amounts of vitamin K in addition to the natural K present in our foods was prudent and could only bring benefit.

Vitamin K functions include:
  • Needed for blood clotting
  • Protects against osteoporosis
  • Prevents oxidative cell damage
  • Is cardioprotective
Natural sources of Vitamin K include: Spinach, Brussels sprouts, Swiss chard, carrots, green string beans, asparagus, red bell peppers, strawberries and eggs, tomatoes, sea plants, green peas, and as synthesized by probiotic organisms. Present Wysong formulations do not contain the synthetic menadione because it has been determined that the inherent vitamin K in ingredients plus the vitamin K produced by Wysong probiotics, combined with special nutrient sparing processing, has made the supplemental addition unnecessary.

A letter to Wysong from an AAFCO official regarding the status of "approved" vitamin K in pet foods. This was in response to our attempt to include natural vitamin K2 in our pet foods, as included in our human foods. Surprisingly, AAFCO will not permit the inclusion of natural vitamin K2, but does permit the use of the synthetic menadione.

Vitamin K3 (menadione) is a precursor that the body can use to make Vitamin K2 (menaquinone), which is an active form of the vitamin. Another active form is called Vitamin K1, which is found in plant tissues. Animals can utilize either of the active forms that are supplied in their diet, or they can make Vitamin K2 from Vitamin K3. Animals cannot make Vitamin K3, however, so it must be provided in the diet or made by intestinal microbes. Either the animal itself or the microbes can then convert Vitamin K3 to Vitamin K2.

Vitamin K is not considered an essential vitamin for dogs, because it does not need to be supplied in the diet. Intestinal microbes can make enough to satisfy a dog's daily requirements. Some dog food manufacturers do add supplemental Vitamin K, however. There is only one source of Vitamin K that FDA does not object to being used in pet food, and that is a form of Vitamin K3 called menadione sodium bisulfite complex (MSBC). Pet food companies sometimes mistakenly list this as menadione sodium bisulfate or bisulfite, but that is a different compound that is not allowed in pet food.

In order to be used in pet foods, ingredients must be FDA-approved feed additives, "generally recognized as safe" (GRAS), or officially defined by AAFCO. Manufacturers must submit a "food-additive petition" or "GRAS notification" to FDA, or an ingredient definition submission to AAFCO, before a particular ingredient can be used in pet food. These submissions are reviewed by FDA, and must show that the ingredient is safe and effective.

Just because something is not defined by AAFCO, however, does not necessarily mean it is unsafe; it may just mean that no one has tried to get it defined yet. Synthetic Vitamin K3 is used in pet food possibly because it might be more cost-effective. Vitamin K2 would either have to be extracted from animal or bacterial tissue, or manufactured from Vitamin K3. This could be more costly.

It may be that because of this, Vitamin K2 has never been submitted to FDA for approval or to AAFCO for an Official Definition. Or if someone has submitted it, it may be that there was not enough information to determine the safety of Vitamin K2. "Synthetic" does not always mean unsafe, and "natural" does not always mean safe.