Vitamin K is probably best known for its role in blood clotting. However, it has many other functions.
Studies have demonstrated vitamin K's role in bone health, the health of arteries, as well as its contribution to the strength of the immune system.
Since vitamin K is available from a variety of foods, and the body has a recycling method of conserving vitamin K, and the intestinal bacteria synthesize vitamin K2 (menaquinones), it is widely thought in the medical community that humans hardly need to think about their vitamin K consumption.
Consumption of lower amounts of vitamin K has been associated with a higher incidence of hip fracture and osteoporosis.
Other studies have demonstrated low levels of vitamin K consumption are associated with arterial calcification.
Additional studies have demonstrated that patients with certain forms of cancer have benefited from consumption of larger than usual doses of vitamin K.
Our most abundant source of vitamin K (vitamin K1, also known as phylloquinone) comes from plants. Leafy green vegetables, such as kale, Swiss chard, and collard greens, have an abundance of vitamin K1. It is also found in high quantities in foods such as broccoli, Brussels sprouts, spinach, and cabbage.
If the above food sources are eaten in sufficient quantity, supplementation with vitamin K should usually not be needed.
Since vitamin K is a fat-soluble vitamin, it is helpful to have fat in a meal when eating food high in vitamin K content.
Anticoagulants, such as warfarin, interfere with vitamin K metabolism. If a patient is taking anticoagulants, a physician's advice should be sought before consuming large quantities of foods rich in vitamin K. Otherwise, it is wise to remember what we were told as children: "Eat those greens!"
References:
Ten Important Facts About Vitamin K That You Need to Know by Dr. Joseph Mercola with Rachael Droege, http://www.mercola.com/2004/mar/24/vitamin_k.htm
Vitamin K by the Linus Pauling Institute, http://lpi.oregonstate.edu/infocenter/vitamins/vitaminK/
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