Vitamin K3, also known as menadione, is a synthetic supplement that acts as a precursor for vitamin K2, the most useful form of vitamin K for the human body. Since menadione does contain some vitamin K activity, it is commonly placed in livestock feed and some pet food to increase nutrient content. The use of vitamin K3 supplements in most developed countries is banned due to its possible side effects, such as damage to internal organs like kidneys or liver. Research on vitamin K3 has shown that it has some effect in combating certain types of cancer, yet research in regards to human safety remains inconclusive.
Menadione is a form of synthetic vitamin K, often sold in supplemental form for its vitamin K-promoting activity. The synthetic version of vitamin K is often called vitamin K3, after its natural forms vitamin K1, found in leafy green vegetables, and vitamin K2, which is synthesized from bacteria. Although vitamin K is needed by the body in large amounts for adequate bone and blood health, the K3 version may not be a suitable alternative for humans. Safety concerns include damage to internal organs such as the kidneys and the liver.
Although menadione for human consumption is banned in most economically developed countries, it is still used in animal feed to help boost nutrient quantity. Some critics propose that K3-induced organ damage can occur in animals, as well, yet research remains inconclusive. K3 vitamins are sometimes found in dog food, as well as livestock feeds, as a cheaper alternative to the natural forms of vitamin K, like vitamin K1 and K2. Animal owners seeking to avoid the synthetic form of this vitamin often opt for natural or organic pet food, containing only naturally derived vitamins and minerals.
Continued research on vitamin K3 has shown that it may have some anti-cancer benefits, especially if combined with vitamin C. The internal effects on other aspects of health, such as the lungs, kidneys or liver, have yet to be determined, and many researchers do not know the full benefits it may have to human health. Some types of skin cancer may be treated or prevented with a topical form of vitamin K3, yet this has not been proven. Almost all research on cancer prevention with menadione shows inconclusive results, but does show promise in future prevention or treatment strategies for skin or prostate cancers.