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Vitamin K

Vitamin K

Description

Vitamin K originates from the German term koajulation. It is also known as antihemorrhagic factor, and is one of the four fat-soluble vitamins necessary for good health. The others are vitamins A, D, and E. The primary and best-known purpose of vitamin K is support of the process of blood clotting. Prothrombin and other clotting factors are dependent on vitamin K for production. It also plays a role in bone health, and may help to prevent osteoporosis . Appropriate growth and development are supported by adequate vitamin K.

There are several forms of the vitamin:

  • K1 or phylloquinone; also known as phytonadione
  • K2, a family of substances called menaquinones
  • K3 or menadione, a synthetic form of this vitamin

General use

The Required Daily Amount (RDA) of vitamin K is 5 micrograms (mcg) for infants less than six months old, 10 mcg for babies six months to one year old, 15 mcg for children aged one to three years, 20 mcg for those aged four to six years, and 30 mcg for those seven to ten years old. Males require 45 mcg from 1114 years, 65 mcg from 1518 years, 70 mcg from 1924 years, and 80 mcg after the age of 24 years. Females need 45 mcg from 1114 years, 55 mcg from 1518 years, 60 mcg from 1924 years, and 65 mcg after the age of 24, and for pregnant or lactating women. These values are based on an estimate of 1 mcg of vitamin K per kilogram of body weight.

The most common use of vitamin K is to supplement babies at birth, thus preventing hemorrhagic disease of the newborn. Routine administration of vitamin K to newborns is, however, being questioned by practitioners of evidence-based nursing. In 2003 the American Academy of Pediatrics (AAP) restated that prevention of bleeding from early vitamin K deficiency by administration of the vitamin is accepted practice. The AAP also noted that a possible link between supplemental vitamin K and early childhood cancer has not been proven as of 2003.

Others who may benefit from supplemental vitamin K include those taking medications that interact with it or deplete the supply. It also appears to have some effectiveness in preventing osteoporosis, but some studies done involved patients using a high dietary intake of the vitamin rather than supplements. In 2003, however, a group of Japanese researchers reported that supplemental doses of vitamin K2 given together with vitamin D3 appeared to reduce bone turnover and sustain bone density in postmenopausal women with mild osteoporosis.

People taking warfarin, a vitamin K antagonist, are able to use the vitamin as an antidote if the serum level of warfarin is too high, increasing the risk of hemorrhage. Vitamin K taken by mouth appears to be more effective than intramuscular injections of the vitamin when it is used to counteract the effects of warfarin.

Vitamin K is also used to treat bleeding from the esophagus and other complications of cirrhosis , a disease of the liver.

Some women find that supplemental vitamin K relieves the symptoms of morning sickness during pregnancy . This treatment is even more effective if vitamin K is taken together with vitamin C .

Topical formulations of vitamin K are sometimes touted as being able to reduce spider veins on the face and legs. The creams are quite expensive and the efficacy is questionable at best. However, recent clinical studies have shown that topical applications of vitamin K given to patients following laser treatments on the face are effective in minimizing bruising from the procedure.

More recently, researchers have been studying vitamin K intensively for its potential anticancer effects. Vitamin K3 in particular may be useful as an adjuvant treatment for ovarian cancer .

Preparations

Natural sources

Dark green leafy vegetables are among the best food sources of vitamin K in the form of K1. Seaweed is packed with it, and beef liver, cauliflower, eggs, and strawberries are rich sources as well. Vitamin K is fairly heat-stable, but gentle cooking preserves the content of other nutrients that are prone to breaking down when heated. Some of the supply for the body is synthesized as vitamin K2 by the good bacteria in the intestines.

Supplemental sources

Vitamin K is not normally included in daily multivitamins, as deficiency is rare. Oral, topical, and injectable forms are available, but should not be used except under the supervision of a health care provider. Injectable forms are by prescription only. Supplements are generally given in the form of phytonadione since it is the most effective form and has a lower risk of toxicity than other types. Synthetic forms of vitamin K are also available for supplemental use.

Deficiency

Deficiency of vitamin K is uncommon in the general population but is of particular concern in neonates, who are born with low levels of vitamin K. Hemorrhagic disease of the newborn can affect infants who do not receive some form of vitamin K at birth. Affected babies tend to have prolonged and excessive bleeding following circumcision or blood draws. In the most serious cases, bleeding into the brain may occur. Most commonly an injection of vitamin K is given in the nursery following birth, but a series of oral doses is also occasionally used. The primary sign of a deficiency at any age is bleeding, and poor growth may also be observed in children.

Chronically low levels of vitamin K are correlated with higher risk of hip fracture in older men and women. A study done in 2003 reported that the current recommended dietary intake for vitamin K in adults may not be adequate for older women.

Risk factors for deficiency

Vitamin K deficiency is unusual, but may occur in certain populations, including those on the medications mentioned in interactions, alcoholics, and people with diseases of the gastrointestinal tract that impair absorption. Conditions that may be problematic include Crohn's disease , chronic diarrhea , sprue, and ulcerative colitis. Anything that impairs fat absorption also risks decreasing the absorption of the fat-soluble vitamins. Long term use of broad spectrum antibiotics destroys the bacteria in the intestinal tract that are necessary for the body's production of vitamin K.

Precautions

Allergic reactions to vitamin K supplements can occur, although they are rare. Symptoms may include flushed skin, nausea , rash, and itching . Medical attention should be sought if any of these symptoms occur. Infants receiving vitamin K injections occasionally suffer hemolytic anemia or high bilirubin levels, noticeable from the yellow cast of the skin. Emergency medical treatment is needed for these babies. Liver and brain impairment are possible in severe cases.

Certain types of liver problems necessitate very cautious use of some forms of vitamin K. Menadiol sodium diphosphate, a synthetic form also known as vitamin K4, may cause problems in people with biliary fistula or obstructive jaundice . A particular metabolic disease called G6-PD deficiency also calls for careful use of vitamin K4. The expertise of a health care professional is called for under these circumstances. Sheldon Saul Hendler, MD, PhD, advises there is no reason to supplement with more than 100 mcg daily except in cases of frank vitamin K deficiency.

Side effects

Oral forms of vitamin K4 may occasionally irritate the gastrointestinal tract. High doses greater than 500 mcg daily have been reported to cause some allergictype reactions, such as skin rashes , itching, and flushing.

Interactions

There are numerous medications that can interfere with the proper absorption or function of vitamin K. The long-term use of antacids may decrease the efficacy of the vitamin, as can certain anticoagulants. Warfarin is an anticoagulant that antagonizes vitamin K. Efficacy of the vitamin is also decreased by dactinomycin and sucralfate. Absorption is decreased by cholestyramine and colestipol, which are drugs used to lower blood cholesterol levels. Other drugs that may cause a deficiency include long-term use of mineral oil, quinidine, and sulfa drugs. Primaquine increases the risk of side effects from taking supplements.

Other types of prescription medications that may cause vitamin K depletion include anticonvulsants (drugs to prevent seizures), including valproic acid; macrolide, aminoglycoside, cephalosporin, and fluoroquinolone antibiotics; phenobarbital; and dapsone (used to treat leprosy and skin infections ).

Resources

BOOKS

Bratman, Steven, and David Kroll. Natural Health Bible. Rocklin, CA: Prima Publishing, 1999.

Griffith, H. Winter. Vitamins, Herbs, Minerals & Supplements: The Complete Guide. AZ: Fisher Books, 1998.

Jellin, Jeff, Forrest Batz, and Kathy Hitchens. Pharmacist's letter/Prescriber's Letter Natural Medicines Comprehensive Database. CA: Therapeutic Research Faculty, 1999.

Pelletier, Kenneth R., MD. The Best Alternative Medicine, Part I: Food for Thought. New York: Simon & Schuster, 2002.

Pressman, Alan H., and Sheila Buff. The Complete Idiot's Guide to Vitamins and Minerals. New York: Alpha Books, 1997.

PERIODICALS

American Academy of Pediatrics Committee on Fetus and Newborn. "Controversies Concerning Vitamin K and the Newborn. American Academy of Pediatrics Committee on Fetus and Newborn." Pediatrics 112 (July 2003) (1 Pt 1): 191192.

Booth, S. L., L. Martini, J. W. Peterson, et al. "Dietary Phylloquinone Depletion and Repletion in Older Women." Journal of Nutrition 133 (August 2003): 25652569.

Crowther, M. A., J. D. Douketis, T. Schnurr, et al. "Oral Vitamin K Lowers the International Normalized Ratio More Rapidly Than Subcutaneous Vitamin K in the Treatment of Warfarin-Associated Coagulopathy. A Randomized, Controlled Trial." Annals of Internal Medicine 137 (August 20, 2002): 251-254.

Iwamoto, J., T. Takeda, and S. Ichimura. "Treatment with Vitamin D3 and/or Vitamin K2 for Postmenopausal Osteoporosis." Keio Journal of Medicine 52 (September 2003): 147150.

Lamson, D. W., and S. M. Plaza. "The Anticancer Effects of Vitamin K." Alternative Medicine Review 8 (August 2003): 303318.

Libby, E. N., and D. A. Garcia. "A Survey of Oral Vitamin Use by Anticoagulation Clinics." Archives of Internal Medicine 162 (September 9, 2002): 1893-1896.

Lucena, M. I., R. J. Andrade, G. Tognoni, et al. "Multicenter Hospital Study on Prescribing Patterns for Prophylaxis and Treatment of Complications of Cirrhosis." European Journal of Clinical Pharmacology 58 (September 2002): 435-440.

Medves, J. M. "Three Infant Care Interventions: Reconsidering the Evidence." Journal of Obstetric, Gynecologic, and Neonatal Nursing 31 (September-October 2002): 563-569.

Shah, N. S., M. C. Lazarus, R. Bugdodel, et al. "The Effects of Topical Vitamin K on Bruising After Laser Treatment." Journal of the American Academy of Dermatology 47 (August 2002): 241-244.

von Gruenigen, V. E., J. M. Jamison, J. Gilloteaux, et al. "The in vitro Antitumor Activity of Vitamins C and K3 Against Ovarian Carcinoma." Anticancer Research 23 (July-August 2003): 32793287.

ORGANIZATIONS

American Academy of Pediatrics (AAP). 141 Northwest Point Boulevard, Elk Grove Village, IL 60007. (847) 434-4000. <http://www.aap.org>.

American Society for Clinical Nutrition. 9650 Rockville Pike, Bethesda, MD 20814. (301) 530-7110. <http://www.faseb.org/ascn>.

American Society of Hematology (ASH). 1900 M Street, NW, Suite 200, Washington, DC 20036. (202) 776-0544. <http://www.hematology.org>.

Judith Turner

Rebecca J. Frey, PhD

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Vitamin K Deficiency

Vitamin K Deficiency

Definition

Vitamin K deficiency exists when chronic failure to eat sufficient amounts of vitamin K results in a tendency for spontaneous bleeding or in prolonged and excessive bleeding with trauma or injury. Vitamin K deficiency occurs also in newborn infants, as well as in people treated with certain antibiotics. The protein in the body most affected by vitamin K deficiency is a blood-clotting protein called prothrombin.

Description

Vitamin K is a fat-soluble vitamin. The recommended dietary allowance (RDA) for vitamin K is 80 mg/day for the adult man, 65 mg/day for the adult woman, and 5 mg/day for the newborn infant. The vitamin K present in plant foods is called phylloquinone; while the form of the vitamin present in animal foods is called menaquinone. Both of these vitamins are absorbed from the diet and converted to an active form called dihydrovitamin K.

Spinach, lettuce, broccoli, brussels sprouts, and cabbage are good sources of vitamin K, containing about 8 mg vitamin K/kg food. Cow milk is also a good source of the vitamin.

A portion of the body's vitamin K is supplied by bacteria living in the intestine rather than by dietary sources.

Vitamin K plays an important role in blood clotting. Without the vitamin, even a small cut would cause continuous bleeding in the body, and death. 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 blood-stream. When an injury occurs, these molecules rapidly assemble and form the blood clot. The clotting factors are proteins, and include proteins called Factor II, Factor VII, Factor IX, and Factor X. Factor II is also called prothrombin. These proteins require vitamin K for their synthesis in the body. The blood-clotting process also requires a dozen other proteins that do not need vitamin K for their synthesis.

Causes and symptoms

Newborns are especially prone to vitamin K deficiency. A nursing-mother's milk is low in the vitamin; breast milk can supply only about 20% of the infant's requirement. Infants are born with low levels of vitamin K in their body; they do not have any vitamin K-producing bacteria in their intestines. Their digestive tracts are sterile. As a result, a form of vitamin K deficiency, called hemorrhagic disease of the newborn, may develop. This disease involves spontaneous bleeding beneath the skin or elsewhere in the infant's body, and occurs in about 1% of all infants. In rare cases, it causes death due to spontaneous bleeding in the brain.

Vitamin K deficiency in adults is rare. When it occurs, it is found in people with diseases that prevent the absorption of fat. These diseases include cystic fibrosis, celiac disease, and cholestasis. Vitamin K deficiency can exist in adults treated with antibiotics that kill the bacteria that normally live in the digestive tract. As mentioned, the intestine-bacteria supply part of our daily requirement of vitamin K. Vitamin K deficiency can result in bleeding gums, and in skin that is easily bruised.

Others who may benefit from supplemental vitamin K include those taking medications that interact with it or deplete the supply. It also appears to have some effectiveness in preventing osteoporosis, but some studies done involved patients using a high dietary intake of the vitamin rather than supplements. In 2003, however, a group of Japanese researchers reported that supplemental doses of vitamin K2 given together with vitamin D3 appeared to reduce bone turnover and sustain bone density in postmenopausal women with mild osteoporosis.

Chronically low levels of vitamin K are correlated with higher risk of hip fracture in older men and women. A study done in 2003 reported that the current recommended dietary intake for vitamin K in adults may not be adequate for older women.

Diagnosis

Vitamin K status is measured by the prothrombin time test. The normal prothrombin time is about 13 seconds. With vitamin K deficiency, the prothrombin time can be several minutes. The test involves taking a sample of blood, placing it in a machine called a fibrometer, and measuring the time it takes for blood-clot formation. Blood-clotting problems can also be caused by a rare genetic disease called hemophilia. Hemophilia is not related to vitamin K deficiency. Once vitamin K deficiency is suspected, further tests must be used to distinguish it from possible hemophilia. Where a bleeding disorder can be corrected by vitamin K treatment, the diagnosis of vitamin K deficiency is proven to be correct.

Treatment

Vitamin K deficiency in newborn infants is treated and prevented with a single injection of phylloquinone (5 mg). Adults with vitamin K deficiency are treated with daily oral doses of 10 mg phylloquinone for one week.

Prognosis

The prognosis for correcting vitamin K deficiency, and associated blood-clotting problems, is excellent.

KEY TERMS

Fat-soluble vitamin Fat-soluble vitamins can be dissolved in oil or in melted fat.

Hemorrhage Bleeding that continues for an abnormally long period of time.

Phylloquinone An alternate name for vitamin K1.

Prothrombin Prothrombin is a blood-clotting protein. Injury to a blood vessel produces a signal which triggers the conversion of prothrombin to thrombin. Thrombin is a protein which plays a central role in provoking the assembly of other proteins to form the blood clot.

Recommended Dietary Allowance (RDA) The Recommended Dietary Allowances (RDAs) are quantities of nutrients in the diet that are required to maintain good health in people. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences, and may be revised every few years. A separate RDA value exists for each nutrient. The RDA values refer to the amount of nutrient expected to maintain good health in people. The actual amounts of each nutrient required to maintain good health in specific individuals differ from person to person.

Water-soluble vitamins Water-soluble vitamins can be dissolved in water or juice.

Prevention

Aside from newborns and young infants, vitamin K deficiency is not a concern for the general population. Vitamin K deficiency can be prevented by assuring that the diet contains such foods as spinach, cabbage, brussels sprouts, and eggs. Soybean oil, canola oil, and olive oil are good sources of the vitamin, while corn oil and peanut oil are very poor sources. Elderly people, especially those living alone, should be checked for adequate intake of the vitamin.

Resources

BOOKS

Pelletier, Kenneth R., MD. The Best Alternative Medicine, Part I: Food for Thought. New York: Simon & Schuster, 2002.

PERIODICALS

American Academy of Pediatrics Committee on Fetus and Newborn. "Controversies Concerning Vitamin K and the Newborn. American Academy of Pediatrics Committee on Fetus and Newborn." Pediatrics 112, no. 1, Part 1 (July 2003): 191-192.

Booth, S. L., L. Martini, J. W. Peterson, et al. "Dietary Phylloquinone Depletion and Repletion in Older Women." Journal of Nutrition 133 (August 2003): 2565-2569.

Iwamoto, J., T. Takeda, and S. Ichimura. "Treatment with Vitamin D3 and/or Vitamin K2 for Postmenopausal Osteoporosis." Keio Journal of Medicine 52 (September 2003): 147-150.

ORGANIZATIONS

American Academy of Pediatrics (AAP). 141 Northwest Point Boulevard, Elk Grove Village, IL 60007. (847) 434-4000. http://www.aap.org.

American Society for Clinical Nutrition. 9650 Rockville Pike, Bethesda, MD 20814. (301) 530-7110. http://www.faseb.org/ascn.

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Vitamin K

Vitamin K

Vitamin K promotes the formation of prothrombin and other blood-clotting proteins in the liver. A deficiency in the vitamin leads both to a slow-down in the clotting process and the strong possibility of a hemorrhage (excessive bleeding).

Dam's Hens

Research into vitamins began in 1929. Danish biochemist Carl Dam (1895-1976) noticed that his laboratory hens developed small hemorrhages (areas of blood vessel breakage) under the skin and within the muscles. Because the hemorrhages resembled those seen in scurvy, Dam first treated the hens for that disease. He added vitamin C in the form of lemon juice to his hens' diet. When that failed to stop their bleeding, he tried other additives. He ended up trying all the food additives that other investigators had found useful in correcting vitamin deficiencies. None of them worked.

Dam concluded that an unknown vitamin must be involved. Since the mysterious vitamin appeared to be essential for normal coagulation (clotting) of the blood, Dam named it vitamin K, for "Koagulation" (the German spelling of "coagulation").

The Search Begins

Intrigued by the thought of a new and potentially useful vitamin, others took up the challenge of the search. Within a few years, several biochemists were able to isolate the vitamin from an extract of alfalfa. An American group led by Edward Doisy (1893-1986) discovered that the alfalfa extract consisted of two chemically similar yellowish oils. The oils became known as KI and K2. Doisy's group went on to work out the chemical constitution of both varieties. Because of this work, Doisy shared the 1943 Nobel Prize for medicine with Dam.

Vitamin K Deficiencies

Vitamin K deficiencies are relatively rare. The vitamin is widespread in plants and it is also synthesized by the bacteria in the human intestinal tract. Because antibiotics often destroy all types of bacteria in the body, patients on long-term drug therapy may need vitamin K supplements to prevent bleeding problems.

Newborn infants are particularly susceptible to vitamin K deficiency. This is because the vitamin does not pass easily from the mother to the fetus through the placenta (birth sac). In addition, all babies are born with a sterile digestive tract.

Because of this, newborns often receive an intramuscular injection of vitamin K at birth. The vitamin is also routinely added to infant formula. This helps prevent hemorrhages. Infants can only begin to synthesize their own vitamin K several days after birth. This is when the digestive tract has acquired the necessary bacteria.

[See also Antibiotic ]

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vitamin K

vitamin K Fat‐soluble vitamin essential for the synthesis of γ‐carboxyglutamate in prothrombin and other proteins involved in the blood clotting system, and bone proteins. Deficiency causes impaired blood coagulation and haemorrhage. Two groups of compounds have vitamin K activity: phylloquinones, found in green plants, and a variety of menaquinones synthesized by intestinal bacteria. Dietary deficiency is unknown, except when associated with general malabsorption diseases. However, some new‐born infants are at risk of haemorrhage as a result of low vitamin K status, and it is general practice to give a single, relatively large dose of the vitamin shortly after birth.

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vitamin K

vitamin K A fat-soluble vitamin consisting of several related compounds that act as coenzymes in the synthesis of several proteins (including prothrombin) necessary for blood clotting. Deficiency of vitamin K, which leads to extensive bleeding, is rare because a form of the vitamin is manufactured by intestinal bacteria. Green vegetables and egg yolk are good sources.

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vitamin K

vitamin K n. a fat-soluble vitamin occurring in two main forms – phytomenadione and menaquinone – essential for the normal clotting of blood. A dietary deficiency does not often occur as the vitamin is synthesized by bacteria in the large intestine and is widely distributed in green leafy vegetables and meat.

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vitamin K

vitamin K A generic term for 2-methyl-1, 4-naphthoquinone and its derivatives; these are fat-soluble vitamins required for the synthesis of prothrombin and also for other clotting factors necessary for its activation. A deficiency of this vitamin causes delayed clotting, and haemorrhaging.

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vitamin K

vi·ta·min K • n. any of a group of vitamins found mainly in green leaves and essential for the blood-clotting process. They include phylloquinone (vitamin K1) and menaquinone (vitamin K2).

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