Vitamin K

Most people don't think too much about what is happening when they cut their finger making dinner.  They grab a tissue and hold it against the cut until it stops bleeding.  The cut is washed off and a small bandage is put on it.

But what made the bleeding stop?  The vitamin K in the bloodstream.

Why People Need Vitamin K

This vitamin is essential for making the blood clots that stop the bleeding whenever a person cuts themselves.  Vitamin K is fat-soluble and actually comes in three forms:

  • Vitamin K1 - Also called phylloquinone.  This is the form of vitamin K found in plant foods.

  • Vitamin K2 - Known as menaquinone.  Vitamin K2 is made by the friendly bacteria in the intestines.

  • Vitamin K3 - Also called menadione.  An artificial form of vitamin K, it ends up in a person's liver, where it is then used to make some of the substances that help the blood clot.

While vitamin K is mainly necessary to help one stop bleeding, it does perform some other tasks as well.  Among these, the most important is the crucial role that vitamin K plays in helping build bones.  This vitamin is needed to help the body hold onto the calcium in the bones and ensure it is getting to the right places.

Recent research regarding vitamin K and cancer is also interesting although further studies are needed.

Vitamin K Requirements

There has only been a daily recommended requirement for vitamin K since 1989.  Until that point, medical researchers thought the body produced all the vitamin K it needed from the bacteria in the intestines.  However, the bacteria produce only half of what a person needs.  The rest of a person's natural vitamin K comes from green, leafy vegetables. 

When the Body is Deficient

Generally speaking, a vitamin K deficiency is fairly rare as almost everyone gets more than enough from their own bacteria and the food they consume.  Sometimes babies have a vitamin K deficiency because their intestines don't have any bacteria to produce it.  To avoid the possibility of a serious bleeding problem called hemorrhagic disease of the newborn, most infants are given a tiny amount of vitamin K by injection soon after birth.

Adults with a vitamin K deficiency usually do not eat enough leafy, green vegetables or they have been taking oral antibiotics for a long period of time.  Antibiotics are known to kill off the intestinal bacteria that produce vitamin K. 

Sometimes vitamin K deficiency is caused by a liver disease or a problem with digesting fat.  A person might be deficient if they have the following:

  • They have a serious liver disease.  Such people cannot use vitamin K properly and their physician will probably recommend vitamin K shots.

  • They suffer from ulcerative colitis, Crohn's disease or some other serious intestinal problem.  These people cannot absorb fats properly and do not absorb enough vitamin K from their food.  A doctor should be consulted about possible supplementation.

  • They have been taking antibiotic pills for several weeks or longer.  Cephalosporin, neomycin and tetracycline all kill the bad bacteria in a person's body.  However, they also kill the good or "friendly" bacteria in the intestines.  Eating more foods containing vitamin K will help, but a doctor should also be consulted.

  • They are taking cholesterol-lowering drugs such as cholestyramine (Questran) or colestipol (Colestid).  Such drugs block the absorption of vitamin K and other fat-soluble vitamins.  Again, a physician should be consulted about possibly taking supplements.

Symptoms of Vitamin K Deficiencies

The major symptom of vitamin K deficiency is that the blood clots too slowly, so a person will bleed for a long time from even very minor injuries.  A deficiency in this vitamin can cause big black-and-blue marks from even slight bruises, or for no reason at all, as well as intestinal bleeding, blood in the urine and nosebleeds.

The anti-clotting drugs heparin and warfarin (Coumadin) are frequently prescribed for elderly people with heart trouble or who are at risk for stroke or other health threats caused by blood clots.  However, these drugs work by blocking the use of vitamin K in the body.

Anyone who suspects they have a vitamin K deficiency should see a physician at once.  Blood tests will need to be conducted to check clotting time and a prothrombin level.  If the test results show a vitamin K deficiency, more tests may be needed to understand why a deficiency exists.

While the physician will probably immediately start vitamin K shots, it may be necessary to take vitamin K supplements until the shots take effect.

Foods Containing Vitamin K

Many foods have not been analyzed for their vitamin K content.  In general, all the leafy vegetables that are dark green in color have a good amount of vitamin K, such as broccoli, kale, lettuce and cabbage.  Strawberries are also a good source for this vitamin.  A few animal foods, such as liver and egg yolks, have smaller amounts of vitamin K.

In a 2006 meta-analysis that examined 13 different trials, researchers discovered that taking vitamin K supplements reduced bone loss and cut the risk of fractures.

Individuals who ensure they get enough vitamin K (especially women) can have a big payoff.  A recent study conducted among 120,000 female nurses showed that among middle-aged and older women, the ones who had the most vitamin K in their diets also had the lowest risk of a hip fracture.



  1. Alan H. Pressman and Sheila Buff.(2007). The Complete Idiot's guide to vitamins and minerals. New York : Alpha Books
  2. Brewer, S. (2010). The essential guide to vitamins, minerals and herbal supplements. London : Right Way
  3. Elson M. Haas, Md & Buck Levin, Phd, Rd.(2006). Staying Healthy with Nutrition: The Complete Guide to diet and nutritional medicine. Berkeley, Calif. : Celestial Art
  4. Holford, P. (2004). The optimum nutrition bible. London : Piatkus
  5. Holford, P & Lawson, S.(2008). Optimum Nutrition Made Easy How to achieve optimum health. London : Piatkus
  6. Lieberman, S. & Bruning, N. (2003). The Real Vitamin & Mineral Book. New York : Avery
  7. Rodale Health Books.(2009). Healing with vitamins : the best nutrients to slow, stop, and reverse disease. Emmaus, Pa. : Rodale
  8. Royston, A.(2003). Vitamins and minerals for a healthy body. Oxford : Heinemann Library
  9. The National Research Council.(1989). Recommended Dietary Allowances, 10th ed, National Academy of Sciences
  10. Werbach, M. (1993). Nutritional Influences on Illness. 2nd ed. Los Angeles: Third Line Press

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