Vitamin K1 is also known as phylloquinone or phytomenadione (also called phytonadione). Vitamin K2 (menaquinone, menatetrenone) is normally produced by bacteria in the Large Intestine, and dietary deficiency is extremely rare unless the intestines are heavily damaged, are unable to absorb the molecule, or due to decreased production by normal flora, as seen in broad spectrum antibiotic use.
There are three synthetic forms of vitamin K, vitamins K3, K4, and K5, which are used in many areas including the pet food industry (vitamin K3) and to inhibit fungal growth (vitamin K5).
Toxicity
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 K and therefore no Tolerable Upper Intake Level (UL) has been set. However, vitamin K3 (menadione) has been shown to be toxic. In fact, the FDA has banned this synthetic form of the vitamin from over-the-counter supplements as large doses have been shown to cause allergic reactions, hemolytic anemia, and cytotoxicity in liver cells.Deficiency
Average diets are usually not lacking in vitamin K and primary vitamin K deficiency is rare in healthy adults. As previously mentioned, newborn infants are at an increased risk of deficiency. Other populations with an increased prevalence of vitamin K deficiency include individuals who suffer from liver damage or disease (e.g. alcoholics), people with cystic fibrosis, inflammatory bowel diseases or those who have recently had abdominal surgeries. Groups which may suffer from secondary vitamin K deficiency include bulimics, those on stringent diets, and those taking anticoagulants. Other drugs which have been associated with vitamin K deficiency include salicylates, barbiturates, and cefamandole, although the mechanism is still unknown. There is no difference between the sexes as both males and females are affected equally. Symptoms of deficiency include heavy menstrual bleeding in women, anemia, bruising, and bleeding of the gums or nose.Osteoporosis and coronary heart disease are strongly associated with lower levels of K2 (menaquinone). Menaquinone is not inhibited by salicylates as happens with K1, so menaquinone supplementation can alleviate the chronic vitamin K deficiency caused by long term aspirin use.
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