|Home > Facts > Vitamin K|
More About:vitamin and k
...king water that is the contaminated with a v
...kor Kwashiorkor The term k
...vitamin B1, is a micronutrient essential for the m...known as vitamin B1, is a micronutrient esse
...vitamin. His daily diet, according to his book, Ja...ks Research and general acceptance Re
...ks Research and general acceptance Resources
...vitamin contents of various foods; and sample menu...ks Research and general acceptance Resources
...vitamin B6, so they must get it from foods in thei...ke vitamin B6, so they must get it from food
...vitamin A, so they must get it from foods in their...ke vitamin A, so they must get it from foods
...vitamins (vitamin D, riboflavin, vitamin...ks Research and general acceptance Resources
...vitamins and minerals. When Mead Johnson found tha...ks Research and general acceptance Resources
Highlight any text in the article to look up more information!
Vitamin K is a fat-soluble organic compound that the body needs to remain healthy. Although bacteria in the human intestine make some vitamin K, it is not nearly enough to meet the body's needs, so people must get most of their vitamin K from foods in their diet.
The liver needs vitamin K to make factors that regulate blood clotting. Vitamin K may also play a role in maintaining strong bones and preventing osteoporosis.
Vitamin K is not a single substance but a collection of chemically similar compounds called naphtho-quinones. Vitamin K1, called phylloquinone, is the natural form of vitamin K. It is found in plants and is the main source of vitamin K in the human diet. Vitamin K2 compounds, called menaquinones, are made by bacteria that live in the human intestine. Researchers originally thought that bacteria in the gut provided a substantial percentage of human vitamin K needs, but more recent research suggests that these bacteria provide only a small amount and that people should get most of their vitamin K from diet. Vitamin K1 is manufactured synthetically and sold many brand names as a dietary supplement. Vitamin
(Illustration by GGS Information Services/Thomson Gale.)
K is also included in many multivitamins. In addition, a synthetic water-soluble form of vitamin K called K3 or menadione is not allowed in dietary supplements in the United States because of its association with serious side effects.
Normal vitamin K requirements
The United States Institute of Medicine (IOM) of the National Academy of Sciences has developed values called Dietary Reference Intakes (DRIs) for vitamins and minerals. The DRIs consist of three sets of numbers. The Recommended Dietary Allowance (RDA) defines the average daily amount of the nutrient needed to meet the health needs of 97–98% of the population. The Adequate Intake (AI) is an estimate set when there is not enough information to determine an RDA. The Tolerable Upper Intake Level (UL) is the average maximum amount that can be taken daily without risking negative side effects. The DRIs are calculated for children, adult men, adult women, pregnant women, and breastfeeding women.
The IOM has not set RDA values for vitamin K because of incomplete scientific information. Instead, in 2000, it set AI levels for all age groups. AI and levels for vitamin K are measured in by weight (micrograms or
mcg). No UL levels have been set for vitamin K. Large amounts of vitamin K1 do not appear to cause blood clotting or other side effects. However, K3 is associated with health risks especially to children. It is banned by the United States Food and Drug Administration.
The following are the AIs for vitamin K for healthy individuals:
Sources of vitamin K
Vitamin K is found in the largest quantities in green, leafy vegetables. The following list gives the approximate vitamin K1 content or some common foods. Little vitamin K is lost during cooking, but more is lost when foods are frozen.
Vitamin K's role in health
Vitamin K is necessary for normal blood clotting (coagulation). In the liver, it is converted into more than half a dozen coenzymes that are essential to the complex cascade of events that result in the formation of a blood clot.
Vitamin K is routinely given to newborns in order to prevent bleeding known as hemorrhagic disease of the newborn (HDN) or vitamin K deficiency bleeding (VKDB) that can occur during the early weeks of life. Although this type of bleeding occurs only in 0.25-1.7% of untreated newborns, it can be fatal. Since 1961, the American Academy of Pediatrics has recommended that all newborns receive a single 0.5-1.0 mg injection of vitamin K1 immediately after birth. As of 2007, there was no equivalent oral (by mouth) supplement available in the United States. A few researchers have questioned whether this early injection of vitamin K increases the risk of developing childhood cancer. In the view of the American Academy of Pediatrics, well-designed research does not support this link.
There is some growing evidence that vitamin K plays a role in maintaining strong bones. Certain proteins that regulate the cells (osteoblasts) that deposit calcium and other minerals in bone appear to be dependent on vitamin K. If this is true, vitamin K may play a role in preventing osteoporosis. Clinical trials are currently underway to determine safety and effectiveness of vitamin K in a variety of situations. Individuals interested in participating in a clinical trial at no charge can find a list of open trials at <http://www.clinicaltrials.gov.>
Vitamin K deficiency
Vitamin K deficiency is extremely rare in healthy people. It can, however, occur in individuals who have disorders that interfere with the absorption of nutrients from the intestine. Signs of vitamin K deficiency include easy bruising, excessive bleeding, and slow clotting. People who are at higher risk for vitamin K deficiency include:
People who are taking blood-thinning drugs, especially warfarin (Coumadin), should discuss their vitamin K needs with their healthcare provider. They may need to restrict their intake of vitamin K. The purpose of blood-thinning drugs is to keep the blood from forming clots in the veins and arteries. Since vitamin K helps blood to clot, high levels of vitamin K in the diet may work against blood-thinning drugs and reduce their effect. Individuals taking these drugs are encouraged to keep their daily intake of vitamin K steady at or slightly below the IA level. In addition, they should have their international normalized ratio (INR) and prothrombin time (PT), both measures of blood clotting potential, checked regularly.
Injections of vitamin K3 (menadione) are banned in the United States because they can cause liver damage and rupture of red blood cells in infants and children.
In addition to interfering with blood-thinning drugs mentioned above, vitamin K may interact with the following:
No complications are expected from vitamin K, especially when most of the vitamin K comes from dietary sources. However, pregnant and breastfeeding women should avoid taking vitamin K supplements. In addition, people taking blood-thinning drugs should carefully monitor their intake of vitamin K so that they do not increase the chance of developing blood clots.
Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Cooper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2001, pp. 162-177. <http://books.nap.edu/books/0309072794/html>
Gaby, Alan R., ed. A-Z Guide to Drug-Herb-Vitamin Interactions Revised and Expanded 2nd Edition: Improve Your Health and Avoid Side Effects When Using Common Medications and Natural Supplements Together. New York: Three Rivers Press, 2006.
Lieberman, Shari and Nancy Bruning. The Real Vitamin and Mineral Book: The Definitive Guide to Designing Your Personal Supplement Program, 4th ed. New York: Avery, 2007.
Pressman, Alan H. and Sheila Buff. The Complete Idiot's Guide to Vitamins and Minerals, 3rd ed. Indianapolis, IN: Alpha Books, 2007.
Rucker, Robert B., ed. Handbook of Vitamins. Boca Raton, FL: Taylor & Francis, 2007.
American Cancer Society. 1599 Clifton Road NE, Atlanta GA 30329-4251. Telephone: 800 ACS-2345. Website: <http://www.cancer.org.>
Linus Pauling Institute. Oregon State University, 571 Weniger hall, Corvallis, OR 97331-6512. Telephone: (541) 717-5075. Fax: (541) 737-5077. Website: <http://lpi.oregonstate.edu/>
Office of Dietary Supplements, National Institutes of Health. 6100 Executive Blvd., Room 3B01, MSC 7517, Bethesda, MD 20892-7517 Telephone: (301) 435-2920. Fax: (301)480-1845. Website: <http://dietary-supplements.info.nih.gov/>
Agricultural Research Service, USDA.“Vitamin K: Another Reason to Eat Your Greens.” United States Department of Agriculture, February 23, 2007. <http://www.ars.usda.gov/is/AR/archive/jan00/green0100.htm>
American Cancer Society.“Vitamin K.” American Cancer Society, March 23, 2006. http://www.cancer.org/docroot/eto/content/ETO_5_3X_Vitamin_K.asp?sitearea=ETO
Higdon, Jane.“Vitamin K.”Linus Pauling Institute-Oregon State University, May 25, 2004. <http://lpi.oregonstate.edu/infocenter/vitamins/VitaminK>
Harvard School of Public Health.“Vitamins.” Harvard University, November 10, 2006. <http://www.hsph.harvard.edu/nutritionsource/vitamins.html>
Medline Plus.“Vitamin K.” U. S. National Library of Medicine, August 1, 2006. <http://www.nlm.nih/gov/medli-neplus/druginfo/natural/patient-vitamink.html>
Warren Grant Magnuson Clinical Center Drug-Nutrient Interaction Task Force.“Important Information to Know When You Are Taking Coumadin and Vitamin K.” National Institutes of Health, December 2003. <http://dietary-supplements.info.nih.gov/factsheets/cc/coumadin1.pdf>
Tish Davidson, A.M.