Vitamin K

What does it do?

Vitamin K is needed for proper bone formation and blood clotting. In both cases, vitamin K does this by helping the body transport calcium. Vitamin K is used by doctors when treating an overdose of the drug warfarin. Also, doctors prescribe vitamin K to prevent excessive bleeding in people taking warfarin but requiring surgery.

There is preliminary evidence that vitamin K2 (menadione), not vitamin K1 (phylloquinone; phytonadione), may improve a group of blood disorders known as myelodysplastic syndromes (MDS).¹ These syndromes carry a significantly increased risk of progression to acute myeloid leukemia. Large-scale trials of vitamin K2 for MDS are needed to confirm these promising early results.

Where is it found?

Leafy green vegetables, such as spinach, kale, collards, and broccoli, are the best sources of vitamin K. The greener the plant, the higher the vitamin K content.² Other significant dietary sources of vitamin K include soybean oil, olive oil, cottonseed oil, and canola oil.³

Vitamin K has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating

Health Concerns

Celiac disease (for deficiency only)

Cystic fibrosis

Osteoporosis

Acute myeloid leukemia (vitamin K2 only)

Morning sickness

Myelodysplastic syndromes (vitamin K2 only)

Phenylketonuria (if deficient)

Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars

Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star

For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Who is likely to be deficient?

A vitamin K deficiency, which causes uncontrolled bleeding, is rare, except in people with certain malabsorption diseases. However, there are reports of severe vitamin K deficiency developing in hospitalized patients who had poor food intake and were receiving antibiotics.⁴ All newborn infants receive vitamin K to prevent deficiencies that sometimes develop in breast-fed infants.

How much is usually taken?

The recommended dietary allowance for vitamin K is about 1 mcg per 2.2 pounds of body weight per day or about 65 to 80 mcg per day for most adults.⁵ This level of intake may be achieved by consuming adequate amounts of leafy green vegetables. However, studies have shown that many men and women aged 18 to 44 years ingest less than the recommended amount of vitamin K.⁶ ⁷

Are there any side effects or interactions?

Allergic reactions to vitamin K injections have been reported on rare occasions.⁸

Vitamin K facilitates the effects of calcium in building bone and proper blood clotting.

Are there any drug interactions?
Certain medicines may interact with vitamin K. Refer to drug interactions for a list of those medicines.

References

1. Miyazawa K, Nishimaki J, Ohyashiki K, et al. Vitamin K2 therapy for myelodysplastic syndromes (MDS) and post-MDS acute myeloid leukemia: information through a questionnaire survey of multi-center pilot studies in Japan. Leukemia 2000;14:1156–7 [letter].

2. Kodaka K, Ujiie T, Ueno T, Saito M. Contents of vitamin K1 and chlorophyll in green vegetables. J Jpn Soc Nutr Food Sci 1986;39:124–6.

3. Booth SL, Centurelli MA. Vitamin K: a practical guide to the dietary management of patients on warfarin. Nutr Rev 1999;57:288–96 [review].

4. Pineo GF, Gallus AS, Hirsh J. Unexpected vitamin K deficiency in hospitalized patients. Can Med Assoc J 1973;109:880–3.

5. Food and Nutrition Board, National Research Council. Recommended Dietary Allowances, 10th ed. Washington, DC: National Academy Press, 1989.

6. Booth SL, Suttie JW. Dietary intake and adequacy of vitamin K. J Nutr 2000;130(1S Suppl):785–8.

7. Booth SL, Webb DR, Peters JC. Assessment of phylloquinone and dihydrophylloquinone dietary intakes among a nationally representative sample of US consumers using 14-day food diaries. J Am Diet Assoc 1999;99:1072–6.

8. Wong DA, Freeman S. Cutaneous allergic reaction to intramuscular vitamin K1. Australas J Dermatol 1999;40:147–52.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2005.