Vitamin K is required by the body for posttranslational modification of certain proteins. These proteins are required for blood coagulation and involved in metabolism pathways in bone and other tissue. Also known as phylloquinone or phytomenadione, and also referred to medically as phytonadione, Vitamin K2 is produced by bacteria in the large intestine, and like other liposoluble vitamins, namely A, D, and E, is stored in the fat tissue of the human body.
Vitamin K: Functions in the Human Body
Vitamin K is needed in the carboxylation of particular glutamate residues in proteins. Caboxylation must take place so that gamma-carboxyglutamate can be formed. Gamma-carboxyglutamate residues, often referred to as Gla-residues, are involved in the binding of calcium. Presently 14 human proteins containing gamma-carboxyglutamate have been identified and they are vital in the regulation of three physiological processes.
- Bone metabolism
- Vascular biology
- Blood coagulation
Vitamin K: Recommended Daily Intake (RDI)
The U.S. Dietary Reference Intake (DRI) for an Adequate Intake (AI) of vitamin K is as follows:
- 25-year old male = 120 micrograms/day
- Adult women = 90 micrograms/day
- Infants = 10–20 micrograms/day
- Children and adolescents 15–100 micrograms/day
Vitamin K deficiency is rare unless the intestines are damaged and unable to absorb the vitamin, or, if there is decreased production by normal flora, which is often caused by broad spectrum antibiotic use.
Vitamin K: Risk of Overdose
There is no known toxicity associated with vitamin K, but allergic reaction from supplementation has been scientifically documented. In light of this no tolerable upper level (UL) has been officially set. However, a synthetic from of vitamin K (K3) called Menadione, has been banned from over the counter sale by the FDA because high doeses cause hemolytic anemia and cytotoxicity in liver cells.
Source: WL
