Vitamin K

What You Need to Know About Vitamin K

Farm worker inspecting organic kale leaves
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Vitamin K is a nutrient that is necessary for blood clotting. Found in a number of vegetables, vitamin K is also available in supplement form or as a cream. Additionally, vitamin K is produced by the bacteria lining your gastrointestinal tract.

Uses for Vitamin K

Vitamin K is typically used to treat blood clotting problems and vitamin K deficiency. In alternative medicine, vitamin K supplements are also purported to promote bone formation and protect against bone diseases like osteoporosis.

In addition, some people take vitamin K to alleviate itching caused by biliary cirrhosis (a liver disease).

Benefits of Vitamin K

There is not yet enough scientific evidence to support the use of vitamin K for any condition apart from vitamin K deficiency and certain bleeding or blood clotting problems, according to the National Institutes of Health (NIH).

However, some studies suggest that vitamin K shows promise for the prevention or treatment of other health problems. Here's a look at some key findings:

1) Bone Health

Vitamin K may improve bone health, according to a 2001 research review published in Nutrition. Sizing up the available data on vitamin K and bone health, the review's authors found that vitamin K can increase bone mineral density and reduce fracture rates in people with osteoporosis. The authors note that vitamin K may be particularly effective when combined with vitamin D, a nutrient known to play a critical role in bone metabolism.

2) Heart Disease

Preliminary findings from animal-based studies indicate that vitamin K may protect against atherosclerosis (hardening of the arteries). However, in a 2008 report from Current Opinion in Lipidology, scientists caution that human-based research on vitamin K1 and heart disease has yielded mixed results.

Foods Rich in Vitamin K

Leafy green vegetables are a top source of vitamin K. In fact, eating just one serving (i.e., a half-cup) of any of the following foods provides more than double your daily requirement for vitamin K:

  • kale
  • spinach
  • turnip greens
  • collard greens
  • Swiss chard
  • parsley
  • mustard greens

Brussel sprouts, broccoli, and romaine lettuce are also rich in vitamin K.

Forms of Vitamin K

Vitamin K1 (also known as phylloquinone) is the natural form of vitamin K found in plants. However, phytonadione (the synthetic version of phylloquinone) is commonly referred to as "vitamin K1" on supplement labels. Vitamin K is also available in other forms, including vitamin K2 (menaquinone) and vitamin K3 (menaphthone or menadione).

According to the NIH, vitamin K1 is less toxic, faster-acting, stronger, and more effective for certain conditions than other forms of vitamin K. Still, some research suggests that intake of vitamin K2 may offer certain health benefits, such as increased protection against heart disease.

Currently, the U.S. Food and Drug Administration prohibits the sale of vitamin K3 in dietary supplements. Injectable vitamin K3 is sometimes used in medical treatments, but there's evidence that these injectable formulas may cause allergic reactions and toxic effects.

Vitamin K is widely available in creams said to treat various skin conditions. Proponents claim that applying vitamin K cream to the skin can remove varicose veins, dark circles under the eyes, bruises, scars, and stretch marks, as well as treat rosacea and speed up the healing of wounds and burns. In most cases, vitamin K creams also contain other natural substances (such as herbal extracts and plant oils).


A very rare condition, vitamin K deficiency occurs when the body can't properly absorb vitamin K from the intestinal tract. This problem may be caused by certain diseases (including cystic fibrosis, celiac disease, and Crohn's disease), long-term use of antibiotics or blood-thinning medications, or treatment with hemodialysis. Signs and symptoms of vitamin K deficiency include excessive bleeding and bruising.


Taking high amounts of vitamin K may be harmful to pregnant and breastfeeding women, patients receiving dialysis treatments due to kidney disease, and people with clotting problems caused by severe liver disease. In addition, vitamin K may interact with certain supplements (including coenzyme Q10, vitamin E). You can get additional tips on using supplements here.

Using Vitamin K for Health

While vitamin K may help with certain health problems, self-treating a condition with vitamin K and avoiding standard care may have serious health consequences. Before you begin using vitamin K, talk to your doctor to determine a safe and effective dosage. Self-treating a condition and avoiding or delaying standard care may have serious consequences.


American Cancer Society. "Vitamin K". October 2010.

Erkkilä AT, Booth SL. "Vitamin K intake and atherosclerosis." Curr Opin Lipidol. 2008 Feb;19(1):39-42.

Gast GC, de Roos NM, Sluijs I, Bots ML, Beulens JW, Geleijnse JM, Witteman JC, Grobbee DE, Peeters PH, van der Schouw YT. "A high menaquinone intake reduces the incidence of coronary heart disease." Nutr Metab Cardiovasc Dis. 2009 Sep;19(7):504-10.

Geleijnse JM, Vermeer C, Grobbee DE, Schurgers LJ, Knapen MH, van der Meer IM, Hofman A, Witteman JC. "Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study." J Nutr. 2004 Nov;134(11):3100-5.

National Institutes of Health. "Vitamin K: MedlinePlus Medical Encyclopedia". May 2011.

National Institutes of Health. "Vitamin K: MedlinePlus Supplements". April 2011.

National Institutes of Health: Office of Dietary Supplements. "Important Information to Know When You Are Taking Coumadin and Vitamin K". Last accessed May 2011.

Weber P. "Vitamin K and bone health." Nutrition. 2001 Oct;17(10):880-7.

Disclaimer: The information contained on this site is intended for educational purposes only and is not a substitute for advice, diagnosis or treatment by a licensed physician. It is not meant to cover all possible precautions, drug interactions, circumstances or adverse effects. You should seek prompt medical care for any health issues and consult your doctor before using alternative medicine or making a change to your regimen.

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