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.
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.1 Other significant dietary
sources of vitamin K include soybean oil, olive oil, cottonseed oil, and canola oil.2
Vitamin K has been used in
connection with the following conditions (refer to the individual
health concern for complete information):
Reliable
and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit. 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.3 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.4 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.56
Are there any side effects or interactions?
Allergic reactions to vitamin K injections have been reported on rare
occasions.7
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 (To view, roll mouse over the "References" heading; to hide, click on the heading)
1. 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.
2. Booth SL, Centurelli MA. Vitamin K: a practical guide to the dietary
management of patients on warfarin. Nutr Rev 1999;57:288–96 [review].
3. Pineo GF, Gallus AS, Hirsh J. Unexpected vitamin K deficiency in
hospitalized patients. Can Med Assoc J 1973;109:880–3.
4. Food and Nutrition Board, National Research Council. Recommended
Dietary Allowances, 10th ed. Washington, DC: National Academy Press, 1989.
5. Booth SL, Suttie JW. Dietary intake and adequacy of vitamin K. J
Nutr 2000;130(1S Suppl):785–8.
6. 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.
7. Wong DA, Freeman S. Cutaneous allergic reaction to intramuscular
vitamin K1. Australas J Dermatol 1999;40:147–52.
The information presented in Aisle7 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.
Reliable
and relatively consistent scientific data showing a substantial health benefit.
