It's often called the forgotten vitamin. It was I discovered in 1934 by a Danish scientist and the letter "K" stands for the Danish spelling of "Koagulation."
Vitamin K is typically the first nutritional supplement that most American children receive as newborn; It helps the liver produce several proteins that control blood clotting. In more recent years, additional benefits have been identified as well. Among those new benefits:
The Heart. In a study of 4,800 people over age 55, researchers in the Netherlands compared those with the lowest and highest intake of vitamin K. Those in the highest intake group were 52 percent less likely to have severe calcification of the aorta, the major artery leading to the heart. The research was published in the international journal of "Nutrition, Metabolism & Cardiovascular Disease" and is summarized on www.healthyfellow.com/138/vitamin-K-and-heart-disease
The Liver. The "Journal of the American Medical Association" reported a Japanese study that found vitamin K may help control the progression of liver cancer and may lower the risk of liver cancer significantly. See www.docguide.com. Search for vitamin K and liver disease research.
Arthritis. Research published in the April 2006 journal "Arthritis & Rheumatism" found that higher blood levels of dietary vitamin K were associated with a lower risk for osteoarthritis of the hand and knee. For more information: use any search engine and enter the keywords "vitamin K deficiency linked to osteoarthritis."
Osteoporosis. Studies at the Harvard Medical School and also in England have found that women with the highest dietary intake of vitamin K had a 30 percent decreased risk for hip fracture. A British researcher analyzing data from 13 Japanese clinical trials found the rate of spinal fractures reduced by 40 percent and hip fractures by 13 percent. Search online for "Harvard and Tufts vitamin K research."
How much is enough? There's no specific RDA for vitamin K for healthy adults. The suggestion is 90 micrograms (mcg) for adult women and 120 for adult men to prevent deficiency. But that's "minimum wage nutrition". Some of the best formulas for bone health contain a lot more than that. OsteoPrime Forte for example, contains 300 mcg.
To maximize your intake, do as you were told as a child: Eat your vegetables-especially the green, leafy variety. The best food sources are collard greens (440 mcg per 100 gram serving) and spinach (380 mcg per 100 gram serving); salad greens are a close third (315 mcg per 100 gram serving).
I think it's interesting that the standard advice from the conventional medical establishment is to avoid vitamin K if you're on blood clotting meds like Coumadin (also affectionately known as "rat poison"). To me, this is another example of the prevailing "wisdom": nothing must interfere with the drugs.
But vitamin K is enormously important for bone health, and the foods containing vitamin K have multiple benefits. Wouldn't it be wiser to simply adjust the medication, rather than eliminating the vitamin and the foods that contain it? Just a thought.
That said, anyone on blood thinning medication should still talk to their doctor. Supplemental vitamin K- or even a diet high in vitamin K containing foods (like salads) - can affect the required dose of blood thinners.