So, what exactly is menadione? And why is it being used in some dog food recipes and not others?
Menadione is actually a vitamin. It’s the man-made version of an essential nutrient commonly known as vitamin K — or more precisely, vitamin K3.
However, K3 is just one of five known versions of vitamin K. The three most common ones found in dog food are:
- Vitamin K1 – naturally found in green leafy vegetables
- Vitamin K2 – produced by bacteria living inside a dog’s gut
- Vitamin K3 – menadione, the man-made synthetic version
Vitamins K1 and K2 are considered natural and fat soluble. So, they’re chemically ready to be used by the body just as they are.
However, vitamin K3 is synthetic. And all forms of the chemical must first undergo the cellular process of alkylation before they can be used by the body.1
So, What’s So Important
About Vitamin K?
Vitamin K is used by the liver to manufacture clotting factors, chemical compounds used by the body to help control bleeding.
So, how much vitamin K does a dog need?
Well, according to the National Academy of Science, not much. A dog needs very little vitamin K per serving to sustain life — only one part per million.2
And most of the vitamin needed by the animal is actually produced by bacteria living within the intestines.
What’s more, the vitamin is not even listed as a required dog food ingredient in the nutrient profiles established by the Association of American Feed Control Officials.3
Menadione — a Nutritional Necessity?
The controversy over menadione appears to be driven by two opposing views.
Supporters4 tend to see menadione as a necessary supplement that dog food manufacturers should include in their recipes.
Defenders favor menadione because…
- Natural vitamin K may lose its potency during processing
- Intestinal disease can prevent gut bacteria from making the vitamin
- Not all manufacturers include green leafy vegetables in their recipes
Advocates also claim menadione should be considered safe because toxic levels are a thousand times greater than the recommended daily dose.
Or a Potential Toxin?
Critics5 see menadione as only a precursor to the vitamin’s more natural versions. They cite (mostly human) studies that make a number of unsettling claims. They worry that menadione can…
- Promote allergic reactions6
- Weaken the immune system
- Cause toxic reactions in liver cells7
- Induce hemolytic anemia (red blood cell toxicity)8
One company selling menadione warns its human buyers that menadione is “toxic to kidneys, lungs, liver, mucous membranes. Repeated or prolonged exposure to the substance can produce target organ damage.”9
Banned from Human Supplements
“Although allergic reaction is possible, there is no known toxicity associated with high doses of the phylloquinone (vitamin K1) or menaquinone (vitamin K2) forms of vitamin K11. The same is not true for synthetic menadione (vitamin K3) and its derivatives. Menadione can interfere with the function of glutathione, one of the body’s natural antioxidants, resulting in oxidative damage to cell membranes. Menadione given by injection has induced liver toxicity, jaundice, and hemolytic anemia (due to the rupture of red blood cells) in infants12; therefore, menadione is no longer used for treatment of vitamin K deficiency13. No tolerable upper level of intake has been established for vitamin K.”
The FDA has banned the use of menadione from over-the-counter supplements because large doses have been shown to cause these dangerous biological effects.14
A Supplement with Many Names
Unfortunately, it can be difficult to spot menadione in a dog food recipe. That’s because manufacturers frequently list the vitamin on a dog food label by one of its more cryptic chemical names:
- Menadione sodium bisulfate
- Menadione sodium bisulfite
- Menadione dimethylprimidinol sulfate
- Menadione dimethylprimidinol sulfite
- Menadione dimethylprimidinol bisulfite
- Dimethylprimidinol sulfate
- Dimethylprimidinol sulfite
- Dimethylprimidinol bisulfate
- Vitamin K supplement
What’s more, you may even come across menadione disguised in seemingly innocent phrases like, “a source of vitamin K activity”.
The Bottom Line
When used in larger doses, menadione can be toxic. However, in trace amounts, like those used in a commercial dog food recipe, menadione is probably safe.
Yet unlike most humans who are inclined to vary their diets with each meal, dogs are typically fed the same food on a continuous basis — meal-after-meal, every day for a lifetime.
And it’s that cumulative exposure of any controversial substance like menadione that tends to keep us up at night.
Because there are currently no AAFCO requirements to include this supplement in any dog food, pet owners may wish to consider the potential long term consequences of including this or any other controversial additive in any food when making a purchase.
- Menadione Fact Sheet ↩
- National Research Council of the National Academy of Sciences ↩
- Official Publication (2008 Edition), Association of American Feed Control Officials, pp. 131-132 ↩
- Aldrich PhD, Greg, “Vitamin K3 – Is It Unnecessary and Toxic?”, www.petfoodindustry.com ↩
- Contreras, Sabine, http://www.DogFoodProject.com ↩
- Prabhu MM et al, Local eczematous allergic reaction to the menadione (vitamin K3) injection, Tm Med J (2005) 55:3 ↩
- M Z Badr et al, Hepatotoxicity of menadione predominates in oxygen-rich zones of the liver lobule, JPET March 1989 vol 248:3 1317-1322 ↩
- Chung SM et al, Adverse consequences of erythrocyte exposure to menadione: involvement of reactive oxygen species generation in plasma, J Toxicol Environ Health A. 2001 Aug 24;63(8):617-29 ↩
- Menadione sodium bisulfite, ScienceLab.com, Houston, TX ↩
- Jane Higdon, PhD, Linus Pauling Institute, Oregon State University (2004); updated Victoria Drake, Ph.D.,
Linus Pauling Institute, Oregon State University (2008), peer-reviewed by Sarah Booth, Ph.D., Director, Vitamin K Research Program, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Vitamin K and the Newborn Reviewed by Dennis T. Costakos, M.D. F.A.A.P., Franciscan Skemp Healthcare-Mayo Health System, Mayo Medical School ↩
- Food and Nutrition Board, Institute of Medicine. Vitamin K. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, D.C.: National Academy Press; 2001:162-196 ↩
- Ferland G. Vitamin K. In: Bowman BA, Russell RM, eds. Present Knowledge in Nutrition. 9th ed. Volume 1. Washington, D.C.: ILSI Press; 2006:220-230 ↩
- Olson RE. Vitamin K. In: Shils M, Olson JA, Shike M, Ross AC, eds. Modern Nutrition in Health and Disease. 9th ed. Baltimore: Lippincott Williams & Wilkins; 1999:363-380 ↩
- Vitamin K Toxicity, Wikipedia, 4/27/2011 ↩