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Menadione (Vitamin K3)

One of the more obscure ingredients found in many pet foods are menadione derivatives - in the form of menadione sodium bisulfate, menadione sodium bisulfite, menadione dimethylprimidinol sulfate, menadione dimethylprimidinol sulfite or menadione dimethylpyrimidinol bisulfite, often listed as "a source of vitamin K activity" or "vitamin K supplement". Unless otherwise noted, these compounds are summarily referred to as "menadione" in this article to make it easier to read.

Watch out:
Some manufacturers leave out the "menadione" part of the above chemical names in their ingredient lists (e.g. you see only "dimethylprimidinol sulfate" listed instead of "menadione dimethylprimidinol sulfate"), and menadione does not only occur in dry and canned foods, but edible chew toys, supplements and treats as well.

Thoroughly research any item with an ingredient list that claims a "source of vitamin K", "source of vitamin K activity" or "vitamin K" in parentheses and contact the manufacturer if you have any questions.

What is it?

Menadione, also known as vitamin K3, is a synthetic version of vitamin K. The natural occuring compounds are vitamin K1 (Phylloquinone, from plant sources) and Vitamin K2 (Menaquinone, synthesized by bacteria in the digestive tract and absorbed by the body). Technically menadione isn't even a vitamin, but a precursor that is converted in the body after ingestion. Natural vitamin K is fat soluble, while menadione derivatives (pure menadione can not be processed) are water soluble and bypass the natural pathway of utilization by the body.

Why is it added to pet food?

Menadione is added as an inexpensive vitamin K supplement in commercial foods. The common statement as to why it is added is "to help with blood clotting", yet it is scientifically proven that the effectivity of menadione on blood clotting is inferior. Even veterinarians will administer vitamin K1 as an antidote to dogs who have for example ingested rat poison, which causes internal bleeding.

Manufacturers who use menadione in their products also like to claim that it is "more stable" than natural vitamin K and has "more nutritional value". Not a single one of them has acknowledged the scientifically proven side effects of this substance.

It is simple to come to a conclusion about the truth in these statements when you consider that

  • not all pet food companies add menadione to their foods and dogs have eaten these products for years without developing deficiencies
  • the National Research Council was not able to demonstrate a dietary requirement for vitamin K in dogs during tests when natural ingredients were fed and
  • fish meals, liver and green plant supplements (e.g. alfalfa, kelp and other seaweed, nettle leaf, blue-green algae, spirulina) are rich sources of natural vitamin K.

Why is it bad?

As a non-native speaker (German is my native language), it has been difficult for me to compose this article in English, since I had to translate most of my information from literature originally written in German. My search for relevant, unbiased sources in English was not very successful, with exception of some obscure references and texts that provided some information but do not include all the facts. There were also many articles written by authors who didn't even have the basic knowledge to differentiate between vtiamin K1, K2 and K3.

Here is a list of negative effects of menadione on the body. It is incomplete, since my English medical terminology is lacking and I was simply not able to translate the more complicated scientific phrases into proper English:

  • causes cytotoxicity in liver cells
  • causes formation of radicals from enzymes of leucocytes, with the consequence of cytotoxic reactions
  • considerably weakens the immune system
  • possible mutagenic effects
  • damages the natural vitamin K cycle
  • has no effect on coumarin derivatives, which are often present in commercial food due to mold contamination (toxic when ingested)
  • causes hemolytic anemia and hyperbilirubinemia, not just linked to large doses
  • disturbs the level of calcium ions (Ca2+) in the body, which is an important factor fibrinolysis
  • is directly toxic in high doses (vomiting, albuminuria), unlike natural vitamin K
  • builds up in tissue and has been detected in eggs, meat and milk of animals supplemented with menadione derivatives
  • causes irritation of skin and mucous membranes
  • causes allergic reactions and eczema

Bässler, K.-H. et al. (1997): Vitamin-Lexikon für Ärzte, Apotheker und Ernährungswissenschaftler. ISBN: 3437211404
DGE (2000): Referenzwerte für die Nährstoffzufuhr. ISBN: 3829571143
Elstner, E. F. (1990): Der Sauerstoff. ISBN: 3411140011
Friedrich, W. (1987): Handbuch der Vitamine. ISBN: 3541120118
Hoehne, Dr. med. vet. Eberhard (1985): Vitamine. ISBN: 3873470284

Things to consider

Menadione (e.g. menadione sodium bisulfate, menadione sodium bisulfite or menadione dimethylpyrimidinol bisulfite)

  • has never been researched or specifically approved for long term use, such as in pet food
  • has been banned from use in food and supplements for human use in many European countries due to serious side effects, including permanent damage and deaths
  • FDA has banned synthetic vitamin K from over-the-counter supplements because of its high toxicity
  • vitamins K1 and K2 are metabolized through the lymphatic system, utilizing pancreatic enzymes and bile acids and regulated by the liver. Vitamin K3 is absorbed directly and bypasses the natural pathways and regulators.

Comments from various sources

(German sources thanks to Christian Schulz)

Deutsche Gesellschaft für Ernährung (translates to German Organization for Nutrition), "Referenzwerte für die Nährstoffzufuhr 2000
The term vitamin K3 for menadione and also its use should be avoided due to considerable side effects, which distinguish the compound from actual vitamin K compounds

Prof. Dr. Wolfram, Technische Universität Munich 12/14/2000
Menadione (vitamin K3) is cheaper because it does not occur naturally. It is also burdened with considerable side effects. It is unsuitable for use in humans.

Hoffmann-La Roche Corporate Health Protection 10/03/2000
The better is always the enemy of the good. Or here: Vitamin K1 is undisputedly better than Vitamin K3.

Hoffmann-La Roche Professional Services 07/30/1999
The background, why Synkavit [a synthetic vitamin K product] was in 1969 removed from the market, was presumably in the realization that vitamin K [here: K1] is practically non toxic in comparison to the K3/K4 versions, and develops a stronger coagulant effect.

Hoffmann-La Roche Professional Services 06/28/1999
SynkavitRoche had hemolytic side effects, as we know today, so that it is assumed that at the time many newborns suffered permanent damage [ed.: there were also deaths]. This prompted the recall of the product in 1967 and instead the harmless Konakion was introduced.

Mark Rosenbloom, MD, MBA, FACEP, Adjunct Associate Professor of Medicine, Emergency Medicine, Feinberg School of Medicine at Northwestern University
This particular toxicity is typically associated with formula-fed infants or those receiving synthetic vitamin K-3 (menadione) injections. Because of its toxicity, menadione is no longer used for treatment of vitamin K deficiency.

Common claims made by employees of the pet food industry

Pet Food Industry Claim:
"Menadione compounds are the only viable source of Vitamin K in commercial pet foods"

My take on it:
A large number of food manufacturers have already proven that this statement is patently false. Many companies have eliminated this questionable ingredient from their formulas, relying on ingredients that are naturally high in vitamin K, or adding the same, completely harmless natural supplement that is for example used to fortify commercial baby food.

Pet Food Industry Claim:
"Menadione is AAFCO approved/self-affirmed GRAS for poultry and swine at nutritionally recommended doses. K3 is in essential all poultry and swine diets. Cost is the only reason AAFCO approval was not also sought for petfood.

My take on it:
Poultry and swine are not cats and dogs - we are looking at a lifetime exposure of several weeks (poultry) to several months (swine) vs. years in cats and dogs. Further, many commercially farmed animals require constant vitamin K supplementation since their intestinal flora is completely wiped out by long-term administration of antibiotics (preventing the beneficial bacteria from producing vitamin K), which does not apply to pets in the same format. Cost is no excuse, especially not considering the profit margins made by manufacturers on pet food. As outlined here on this site itself, menadione is being removed from more and more products - what does that tell us?

Pet Food Industry Claim:
"Menadione has not be shown to create any detrimental effects at levels within 10x of recommended levels. (toxicity reports being utilized by this latest group of "activist" are not only disputed but at mega dose levels with no relevance to actual practice)"

My take on it:
I don't know which "activists" make such claims, but I'd like to point out that I do not support the use of any amount of menadione. It has never been researched or specifically approved for long term use, such as in pet food, and the detrimental effects are not just simply related to high levels, but also to long-term exposure to low levels. Again I have to point out we aren't looking at livestock or lab animals just being exposed for a relatively short period of time, but what this substance can do to pets, especially their immune systems, over a period of 10-15 years or longer.

Pet Food Industry Claim:
"Menadione is utilized to prevent nutrient deficiencies and not acute situation such as Rat poisoning."

My take on it:
This is correct, because menadione has been proven to be entirely ineffective for blood clotting, yet some manufacturers still using menadione compounds (often disguised as "vitamin K supplement") give "aids blood clotting" as a selling point. I call that consumer deception.

Pet Food Industry Claim:
"If products were to be ranked in regards to bioactivity, of course K1 is better than K3, but if we look at application efficacy K3 is better than K1. It is a question of practicality of application.""

My take on it:
Cost vs. efficacy might be a selling point to livestock farmers, but manufacturers selling products for the pet market should realize that pet owners want to do right by their pets and keep them healthy as long as possible. In my personal opinion there is no room for the "least cost principle" in the pet food niche, especially not when many manufacturers claim to have our pets' best interests in mind.

Pet Food Industry Claim:
"The credibility of the anti-menadione arguments are very weak.

My take on it:
Just because someone with a commercial interest in using a less costly product says my arguments are weak doesn't make them so. I think I have listed enough accredited, scientific sources in my article that outline why it is not a bad idea to avoid menadione in a food, under the best of circumstances it is an unnecessary ingredient and under the worst it may be harmful. The fact that my sources are not written in English has nothing to do with the argument - the pet food companies make enough profit to be able to hire certified staff for translating these sources if they were really interested in learning about the other side of the argument. As it is they don't care about anything but protecting their own interests though, and European research seems to be either touted or bashed, depending on which is more convenient in a particular argument.

Pet Food Industry Claim:
"It seems the same folks advocating no Menadione are also in favor of non-processed diets for their pets.""

My take on it:
Not necessarily. Many people simply want good quality commercial diets without unnecessary or harmful ingredients for their pets, and they have a right to be informed.

Pet Food Industry Claim:
"Dr John Suttie retired Research Prof, Univ of Wisconsin to the people in Germany who started this whole issue with Vitamin K in pet foods many years ago. He has published in excess of 225 paper on menadione, Vitamin K1, 2 and 3. In short he knows more about Vitamin K than any of us will ever want to know. When we had this problem in the early 2000's I sent all the files and publications from Germany and he did this rebuttal to their pseudo science. We were never able to understand what the problem was with these people, but after this letter we did not hear from them again until this latest discover from this nutritional guru in California."

My take on it:
On the day Dr. Suttie, or any person in favor of utilizing menadione in commercial pet food, is able to provide the favorable results of a properly conducted, independently funded, long-term study on the effect of menadione on domestic pets, I will stand down on the issue. Until then, unfortunately, I will have to continue to look at it from a "worst case scenario" point of view, just like I do in regards to synthetic preservatives, various rendered and non-rendered animal materials and other poor quality ingredients deemed appropriate for use in pet food by AAFCO.

In the case of human food additives and supplements, it has to be proven that they are not harmful before they are allowed to be included, why should we be satisfied with the reverse scenario for ingredients in the food our pets eat, often for many years, and listen to someone with a vested interest telling us that there's nothing wrong?

Wouldn't you rather buy from a company that respects your wishes than one that touts bits and pieces of regulation while conveniently leaving out others?


In my opinion, Michael von Lüttwitz and Herbert Schulz worded it best in their article "Vitamin K3: eine Geissel im Gesundheitssektor?" [Vitamin K3: a scourge in the health sector?], published in the May 2003 issue of "Der Deutsche Schäferhund" (the professional journal of the Swiss German Shepherd Club):

"When food contains menadione, every owner and breeder has to make the decision for himself whether he can take responsibility for giving his dog a substance that is not permitted in the [human] food sector and led to permanent damage and deaths in humans."

I agree 100% and after presenting the information, as always, I leave the decision up to you.

News Updates on this topic:

November 9th, 2005
February 16th, 2006
May 19th, 2006
May 22nd, 2006
August 29th, 2006
September 14th, 2006
March 30th, 2007

Looks like slowly but surely we are seeing this unnecessary ingredient disappear at least from the higher quality foods! Thanks to everyone who has helped, and is continuing to help bringing this concern to the manufacturers.

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