By Nilesh Patel, NOW Research and Development Dept.
Vitamins are, by definition, essential for human growth and health. They are usually found in the foods we eat. Vitamin K is necessary for normal clotting of the blood. Although Vitamin K deficiencies are rare, they can lead to problems with blood clotting and excessive bleeding.
Fat-soluble vitamins [for example: Vitamin A (trans-Retinol), Vitamin D (Calciol), Vitamin E (á-tocopherol), and Vitamin K (Phylloquinone)] are all polyprenyl compounds (similar to steroids) synthesized from a five-carbon molecule (isoprene). Phylloquinone (C31H46O2), the most common form of Vitamin K, is found in plants as a photosynthetic electron carrier (mostly isolated from alfalfa, commercially), and is the preparation of choice marketed under the generic name of phytonadione. In other words, Phylloquinone is also called phytonadione; both terms refer to the fat-soluble natural Vitamin K (Vitamin K1) used for nutritional supplementation.
(Technical note: The term Vitamin K refers to a group of 2-methyl-1,4-napthoquinone derivatives which can fulfill an essential co-factor function in humans, aiding in the biosynthesis of a number of calcium-binding proteins, some of which are essential for homeostasis (normal biological equilibrium). The natural forms are substituted in position 3 with an alkyl side chain. Vitamin K1 (phylloquinone) has a phytyl side chain in position 3, where as Vitamin K2 has an isoprenyl side chain at position 3.)
Vitamin K is essential since the 1,4-napthoquinone compound cannot be synthesized in the body. In nature, Vitamin K occurs as phylloquinone in plants and as menaquinones produced by bacteria, another significant source. There are three notable forms of Vitamin K:
K1 (phytonadione/ phylloquinone/ phytonactone);
K2 (menaquinones), which can be formed naturally by the bacteria in the intestines (note: K1 is converted to K2 in the body); and
K3 (menadione), which is the most active of the synthetic forms of Vitamin K and is a water-soluble vitamin not used as a prophylaxis (preventative vitamin) because of its potential to cause hemolytic anemia with jaundice.
Absorption of K1 is from the gut (duodenum and jejunum) via the lymphatic system. Thus, conditions that impair the fat absorption will also affect the absorption of Vitamin K. Antibiotics destroy the beneficial bacteria in the intestine needed for Vitamin K synthesis. All forms of Vitamin K have a common basic structure that acts as a cofactor for the enzymes essential for normal blood clotting, namely, in forming the blood clotting chemical prothrombin (Factor II).
In the liver, Vitamin K plays an important role in the actions of coagulation (blood clotting) factors [Proconvertin (Factor VII), Stuart-Power factor (Factor X), & Christmas factor (Factor IX)]. The following are also dependent on Vitamin K: protein C, protein S, and protein Z, along with anti-coagulants proteins C, S, and Z. Phytonadione (K1) is an analogue of Vitamin K, but it has the quickest onset of action, the most prolonged duration, and is the most potent of all the Vitamin K forms. K1 is safer than menadione (K3) to use on newborns. Vitamin K3 is the only form that could cause toxicity, causing hemolytic anemia (due to dying red blood cells), causing jaundice, liver damage and severe neurological damage.
Natural Vitamin K is required for two bone matrix proteins: osteocalcin and matrix-Gla (gamma carboxyglutamic acid). Gla is an amino acid that is part of certain proteins that control calcium. Vitamin K is shown to be beneficial in bone health because it helps to produce the natural protein osteocalcin. Vitamin K adds carboxyl groups to osteocalcin and other proteins that build and maintain bones by binding to (“chelating”) calcium. This is a self-limiting process (similar to hydroxylation of collagen by Vitamin C). Calcium needs these proteins to crystallize and strengthen bone tissue. Vitamin K has been approved for the treatment of osteoporosis in Japan. Thus, Vitamin K is required for proper bone formation and blood clotting. In both cases, Vitamin K accomplishes the job by assisting the body in transporting calcium*.
Green leafy vegetables (spinach, kale, parsley, cilantro, and broccoli) and certain vegetable oils (soybean oil, olive oil, cottonseed oil and canola oil) are good food sources of Vitamin K1. Hydrogenation of oils produces a biologically non-active form of Vitamin K called dihydrophylloquinone. The RDA for Vitamin K ranges from about 65mcg for adult females to 80mcg for adult males, per day.
Deficiency symptoms of Vitamin K manifest as decreased clotting, nosebleeds, increased blood pressure, hemorrhages, and diarrhea.
Precautions: Vitamin K should not be taken without prior medical consultation if pregnancy is suspected or if one is breast-feeding. Antibiotics and certain steroidal preparations may deplete or interfere with Vitamin K. Blood-thinning medications like warfarin and dicumarol will adversely interact with Vitamin K. Vitamin K inhibitors include: x-rays, radiation, aspirin, mineral oil, and laxatives. High amounts of Vitamins A and E can actually block Vitamin K, necessitating supplementation to compensate.
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*These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure or prevent any disease. All information is given for educational purposes ONLY and should not replace the advice of a physician.