Vitamin K
Vitamin K is a fat-soluble vitamin, so it is stored in the body's fat tissue and liver. It is best known for its role in helping blood clot (coagulate) properly (the "K" comes from its German name, Koagulationsvitamin). Vitamin K also plays an important role in bone health. It is rare to have a vitamin K deficiency, because in addition to being found in leafy green foods, the bacteria that are found in the intestines can make vitamin K. Sometimes taking antibiotics can kill the bacteria and lead to a mild deficiency. Vitamin K deficiency can lead to excessive bleeding (hemorrhage), which may begin as oozing from the gums or nose. Other circumstances that may lead to vitamin K deficiency include:

arw Health problems that can prevent the absorption of vitamin K (such as gallbladder or biliary disease, which may alter the absorption of fat), cystic fibrosis, celiac disease, and Crohn's disease

arw Liver disease

arw Use of blood-thinning medications (such as warfarin)

arw Continuing hemodialysis

arw Serious burns
There are 3 forms of vitamin K:

arw Vitamin K1 (phylloquinone, the natural version of K1 and phytonadione, the synthetic type of K1)

arw Vitamin K2 (menaquinone)

arw Vitamin K3 (menaphthone or menadione)

K1 and K3 are both available as part of multivitamin complexes or alone, in 5 mg tablets. These fat-soluble forms are an excellent source of vitamin K. Water-soluble chlorophyll is the most common form of vitamin K found over the counter. It is available in tablet, capsule, and liquid forms.

What is Vitamin K ?
Vitamin K is a group of 2-methilo-naphthoquinone derivatives. There are three notable forms of vitamin K, K1 (phytonadione, phylloquinone, phytonactone , K2 (menaquinones), which can be formed by natural bacteria in the intestines, and K3 (menadione), the most active synthetic form of the preparations K3-K7. Plants synthesize phylloquinone, also known as vitamin K1. Vitamin K1 or phylloquinone is the principal dietary source of vitamin K and its predominant circulating form. Vitamin K2 is the collective term for a group of vitamin K compounds called menaquinones. The menaquinone homolgues are characterized by the number of isoprene residues comprising the side chain. Vitamin K2 is found in chicken egg yolk, butter, cow liver, certain cheeses and fermented soybean products such as natto. Very little vitamin K is stored by the body; small amounts of this vitamin are deposited in the liver and in the bones, but this amount is only enough to supply the body's needs for a few days.

Vitamin K is involved in the carboxylation of certain glutamate residues in proteins to form gamma-carboxyglutamate residues. These proteins have in common the requirement to be post-translationally modified by carboxylation of glutamic acid residues (forming gamma-carboxyglutamic acid) in order to become biologically active. These proteins include the vitamin K-dependent coagulation factors II (prothrombin), VII (proconvertin), IX (Christmas factor), X (Stuart factor), protein C, protein S, protein Zv and a growth-arrest-specific factor (Gas6). Menadione is a fat-soluble vitamin precursor that is converted into menaquinone in the liver. The primary known function of vitamin K is to assist in the normal clotting of blood, but it may also play a role in normal bone calcificaton. Without vitamin K, the carboxylation does not occur and the proteins that are synthesized are biologically inactive.

Where it is found
Rich sources of vitamin K include broccoli, Brussels sprouts, cabbage, cauliflower, kale, spinach and soybeans. Cooked dark green vegetables, such as spinach, kale and broccoli, can provide more than one RDA in a single serving. Cow milk is also a good source of the vitamin. Asian soy foods also are excellent vitamin K sources. Hydrogenation of vegetable oils may decrease the absorption and biological effect of dietary vitamin K. Phylloquinone (vitamin K1) is the major dietary form of vitamin K. Bacteria that normally colonize the large intestine synthesize menaquinones (vitamin K2), which are an active form of vitamin K.

See Vitamin K related videos:
video icon Vitamin K: (video module - 2.47 minutes)
Product related PDF file
Vitamin K Explained

Benefits / uses
Vitamin K plays an important role in blood clotting and bone metabolism (carboxylation of osteocalcin). High serum concentrations of undercarboxylated osteocalcin and low serum concentrations of vitamin K are associated with lower bone mineral density and increased risk of hip fracture. Vitamin K supplements may improve bone mass in postmenopausal women. Vitamin K prevents calcification of arteries and other soft tissue. Calcification of organs and other soft tissue is an adverse consequence of aging. Vitamin K may play a role in the regulation of blood sugar. The pancreas, which makes insulin, has the second highest amount of vitamin K in the body.

Vitamin K and blood clotting - Vitamin K's primary function is to regulate normal blood clotting. Blood clotting is a process that begins automatically when any injury produces a tear in a blood vessel. The process of blood clotting involves a collection of molecules, which circulate continuously through the bloodstream. Vitamin K regulates normal blood clotting by helping the body transport calcium. Protein Z appears to enhance the action of thrombin by promoting its association with phospholipids in cell membranes. Protein C and protein S are anticoagulant proteins that provide control and balance in the coagulation cascade. Vitamin K2, not vitamin K1 (phylloquinone; phytonadione), may improve a group of blood disorders known as myelodysplastic syndromes.
Vitamin K and bone health - Vitamin K supplements improve bone health and reduce risk of bone fractures, particularly in postmenopausal women who are at risk for osteoporosis. Three vitamin-K dependent proteins have been isolated in bone. Higher vitamin K levels correspond to greater bone density, while low levels of vitamin K have been found in those with osteoporosis. In bones, vitamin K mediates the gamma-carboxylation of glutamyl residues on several bone proteins, notably osteocalcin. Osteocalcin is a protein synthesized by osteoblasts (bone forming cells). The mineral-binding capacity of osteocalcin requires vitamin K-dependent gamma-carboxylation of three glutamic acid residues.

Vitamin K and liver diseases - Vitamin K is used to reduce risk of bleeding in liver disease, jaundice, malabsorption, or in association with long-term use of aspirin or antibiotics. Gastrointestinal problems that decrease the absorption of vitamin K, such as obstructions in the bile duct, cystic fibrosis, sprue, Crohn's disease, colitis and medications that reduce the absorption of this vitamin, such as antibiotics.

Vitamin K deficiency in those with cystic fibrosis is worsened by their recurrent need for antibiotics. Vitamin K has been used in the treatment of heavy menstrual bleeding, and with vitamin C to treat morning sickness. Newborns are at risk for bleeding in the brain because of the trauma of coming through the birth canal during delivery.

When to take/Types to take:
Vitamin K supplements are best taken with meal.
Various types of vitamin K include (aka, phytonadione and phylloquinone and), k2 (aka, menaquinone and menatetrenone) and k3 (aka, menadione and napthoquinone). Other forms of vitamin k are available by prescription.

Daily intake for dietary vitamin K (according to the U.S. RDA) is listed below:

arw Infants birth - 6 months: 2 mcg

arw Infants 7 - 12 months: 2.5 mcg

arw Children 1 - 3 years: 30 mcg

arw Children 4 - 8 years: 55 mcg

arw Children 9 - 13 years: 60 mcg

arw Adolescents 14 - 18 years: 75 mcg
A single injection of vitamin K is also given at birth.

arw Males 19 years and older: 120 mcg

arw Females 19 years and older: 90 mcg

arw Pregnant and breastfeeding females 14 - 18 years: 75 mcg

arw Pregnant and breastfeeding females 19 years and older: 90 mcg

Possible Side effects / Precautions / Possible Interactions:
There is no known toxicity associated with high doses of phylloquinone (vitamin K1), menaquinone (vitamin K2), or menadione (vitamin K3) and its derivatives. High intake of vitamin K is not recommended for individuals taking anticoagulant medications such as Warfarin (coumadin).

Possible Interaction:
If you are currently being treated with any of the following medications, you should not take vitamin K without first talking to your health care provider.
Antibiotics -- Antibiotics, particularly a class known as cephalosporins, reduce the absorption of vitamin K in the body. Long-term use (more than 10 days) of antibiotics may result in vitamin K deficiency because these drugs kill not only harmful bacteria but also beneficial, vitamin K-activating bacteria. This is not likely to occur in people who already have low levels of vitamin K or are at risk for deficiency (such as those who are malnourished, elderly, or taking warfarin). Cephalosporins include:

arw Cefamandole (Mandol)

arw Cefoperazone (Cefobid)

arw Cefmetazole (Zefazone)

arw Cefotetan (Cefotan)

Research studies / References
arw Bell RG, Sadowski JA, Matschiner JT. Mechanism of action of warfarin. Warfarin and metabolism of vitamin K1. Biochem. 1972;11:1959-1961.

arw Booth SL, Centurelli MA. Vitamin K: a practical guide to the dietary management of patients on warfarin. Nutr Rev. 1999;57(9 Pt 1):288-293.

arw .Booth SL, Al Rajabi A. Determinants of vitamin K status in humans. Vitam Horm. 2008;78:1-22.

arw Booth SL, Charnley JM, Sadowski JA, Saltzman E, Bovill EG, Cushman M. Dietary vitamin K1 and stability of oral anticoagulation: proposal of a diet with constant vitamin K1 content. Thromb Haemost. 1997;77(3):504-509.

arw Breen GA, St. Peter WL. Hypoprothrombinemia associated with cefmetazole. Ann Pharmacother. 1997;31(2):180-184.

arw Bugel S. Vitamin K and bone health in adult humans. Vitam Horm. 2008;78:393-416.

arw Crowther MA, Julian J, McCarty D, et al. Treatment of warfarin-associated coagulopathy with oral vitamin K: a randomized controlled trial. Lancet. 2000;356(9241):1551-1553.

arw Feskanich D, Weber P, Willett WC, Rockett H, Booth SL, Colditz GA. Vitamin K intake and hip fractures in women: a prospective study. Am J Clin Nutr. 1999;69:74-79.

arw Goldman L, Ausiello D. Cecil Medicine, 23rd ed. Philadelphia, PA: Saunders Elseveir. 2007;181.

arw .Harrell CC, Kline SS. Vitamin K -- supplemented snacks containing olestra: implication for patients taking warfarin [letter]. JAMA. 1999;282(12):1133-1134.

arw Hathcock, JN. Metabolic mechanisms of drug-nutrient interactions. Fed Proc. 1985;44(1):124-129.

arw Hey E. Effect of maternal anticonvulsant treatment on neonatal blood coagulation. Arch Dis Child Fetal Neonatal Ed. 1999;81(3):F208-210.

arw Huilgol VR, Markus SL, Vakil NB. Antibiotic-induced iatrogenic hemobilia. Am J Gastroenterol. 1997;92(4):706-707.

arw Iwamoto I, Kosha S, Noguchi S, Murakami M, Fujino T, Douchi T, et al. A longitudinal study of the effect of vitamin K2 on bone mineral density in postmenopausal women: a comparative study with vitamin D3 and estrogen-progestin therapy. Maturitas. 1999;31(2):161-164.

arw Keith DA, Gundberg CM, Japour A, et al. Vitamin-K dependent proteins and anticonvulsant medication. Clin Pharmacol Ther. 1983;34(4):529-532.

arw Kitchin B, Morgan SL. Not just calcium and vitamin D: other nutritional considerations in osteoporosis. Curr Rheumatol Rep. 2007 Apr;9(1):85-92. Review.

arw Knodel LC, Talbert RL. Adverse effects of hypolipidaemic drugs. Med Toxicol. 1987;2(1):10-32.

arw Kohlmeier M, Saupe J, Shearer MJ, Schaefer K, Asmus G. Bone health of adult hemodialysis patients is related to vitamin K status. Kidney Int. 1997;51:1218-1221.

arw Koonsvitsky BP, Berry DA, Jones MB, et al. Olestra affects serum concentrations of alpha-tocopherol and carotenoids but not vitamin D or vitamin K status in free-living subjects. J Nutr. 1997;127(8 Suppl):1636S-1645S.

arw Lubetsky A, Dekel-Stern E, Chetrit A, Lubin F, Halkin H. Vitamin K intake and sensitivity to warfarin in patients consuming regular diets. Thromb Haemost. 1999;8:396-399.

arw Matsui MS, Rozovski, SJ. Drug-nutrient interaction. Clin Ther. 1982;4(6):423-440.

arw McCormick RK. Osteoporosis: integrating biomarkers and other diagnostic correlates into the management of bone fragility. Altern Med Rev. 2007 Jun;12(2):113-45. Review.

arw National Academy of Science. Recommended Daily Allowances. Accessed August 1, 2007.

arw Nutrients and Nutritional Agents. In: Kastrup EK, Hines Burnham T, Short RM, et al, eds. Drug Facts and Comparisons. St. Louis, Mo: Facts and Comparisons; 2000.

arw Ong T, Whong WZ, Stewart J, and Brockman HE. Chlorophyllin: a potent antimutagen against environmental and dietary complex mixtures. Mutation Research. 1986;173:111-115.

arw Prince DM, Welshenbach MA. Olestra: a new food additive. J Am Diet Assoc. 1998;98(5):565-569.

arw Rashid M, Durie P, Andrew M, et al. Prevalence of vitamin K deficiency in cystic fibrosis. Am J Clin Nutr. 1999;70(3):378-382.

arw Schlagheck TG, Riccardi KA, Zorich NL, Torri SA, Dugan LD, Peters JC. Olestra dose response on fat-soluble and water-soluble nutrients in humans. J Nutr. 1997;127(8 Suppl):1646S-1665S.

arw Shils ME, Olson JA, Shike M, Ross CA, eds. Modern Nutrition in Health and Disease. 9th ed. New York, NY: Lippincott, Williams & Wilkins; 1999.

arw Shiraki M, Shiraki Y, Aoki C, Miura M. Vitamin K2 (menatetrenone) effectively prevents fractures and sustains lumbar bone mineral density in osteoporosis. J Bone Miner Res. 2000;15(3):515-523.

arw .Suzuki K, Fukushima T, Meguro K, et al. Intracranial hemorrhage in an infant owing to vitamin K deficiency despite prophylaxis. Childs Nerv Syst. 1999;15(6-7):292-294.

arw Tamatani M, Morimoto S, Nakajima M, et al. Decreased circulating levels of vitamin K and 25-hydroxyvitamin D in osteopenic elderly men. Metabolism. 1998;47:195-199.

arw Thornquist MD, Kristal AR, Patterson RE, et al. Olestra consumption does not predict serum concentrations of carotenoids and fat-soluble vitamins in free-living humans: early results from the sentinel site of the olestra post-marketing surveillance study. J Nutr. 2000;130(7):1711-1718.

arw Weber P. The role of vitamins in the prevention of osteoporosis--a brief status report. Int J Vitam Nutr Res. 1999;69(3):194-197.

arw Weibert RT, Le DT, Kayser SR, et al. Correction of excessive anticoagulation with low-dose oral vitamin K1. Ann Intern Med. 1997;126(12):959-962.

arw Whitlock RP, Crowther MA, Warkentin TE, Blackall MH, Farrokhyar F, Teoh KH. Warfarin cessation before cardiopulmonary bypass: lessons learned from a randomized controlled trial of oral vitamin K. Ann Thorac Surg. 2007 Jul;84(1):103-8.

arw .Wilson DC, Rashid M, Durie PR, et al. Treatment of vitamin K deficiency in cystic fibrosis: effectiveness of a daily fat-soluble vitamin combination. J Pediatr. 2001;138(6):851-855.