Vitamin K is a group of fat-soluble vitamins your body needs for normal blood clotting. They're also important for maintaining bone health. There are two natural types of vitamin K: phylloquinone and menaquinone.
Phylloquinone, also known as vitamin K1, is made by plants, so it makes up most of the vitamin K you get from your diet. Phylloquinone is found in green, leafy vegetables, okra, asparagus (find out why asparagus makes your urine smell funny), prunes, avocado, canola, olive and soybean oils.
Menaquinone (vitamin K2) is made by probiotic bacteria in the digestive tracts of animals, and is found in small amounts in meat, fish and fermented foods. A third type of vitamin K, menadione, is a synthetic form of vitamin K and is not used in humans.
The Food and Nutrition Board of the Institute of Medicine has determined the adequate intake of vitamin K for all age groups:
- 7 to 12 months: 2.5 mcg (micrograms) per day
- 1 to 3 years: 30 mcg per day
- 4 to 8 years: 55 mcg per day
- 9 to 13 years: 60 mcg per day
- 14 to 18 years: 75 mcg per day
- Males 19 and older: 120 mcg per day
- Females 19 and older: 90 mcg per day
Vitamin K is also available as a dietary supplement. It may interact with certain anticoagulant medications, so don't take vitamin K supplements before talking to your healthcare provider.
American Cancer Society. "Vitamin K." Accessed June 15, 2011. http://www.cancer.org/Treatment/TreatmentsandSideEffects/ComplementaryandAlternativeMedicine/HerbsVitaminsandMinerals/vitamin-k.
Food and Nutrition Board of the Institute of Medicine. "Dietary Reference Intakes - Vitamins." Accessed June 15, 2011. http://iom.edu/~/media/Files/Activity%20Files/Nutrition/DRIs/DRI_Vitamins.pdf
U.S. National Library of Medicine - MedlinePlus. "Vitamin K." Accessed June 15, 2011. http://www.nlm.nih.gov/medlineplus/druginfo/natural/983.html.