We Need to Shop More Often at the K Mart!
Vitamin K has long been known as essential to normal blood clotting--and it is on this basis that the recommended daily allowance (RDA) was established at the very low levels required: 65 micrograms for women and 80 micrograms for men. However, recent research has shown another very important function of vitamin K, for which much larger amounts are required.
Osteocalcin is a protein involved in bone growth, but to do its job properly, it must be saturated with something called carboxyl groups--a process called carboxylation, in which vitamin K is essential. With insufficient vitamin K in the diet, carboxylation is incomplete, and osteocalcin fails in its function of strengthening bone structure.
A French study found that older women whose osteocalcin was undercarboxylated were almost twice as likely to sustain hip fracture as women with adequate osteocalcin carboxylation. Other studies have corroborated these findings, while still other studies have implicated the role of vitamin K. Now a Tufts University study has found that as much as 420 micrograms of vitamin K may be required daily to achieve effective osteocalcin carboxylation.
Fortunately, it is not difficult to get that much vitamin K from the food we eat, particularly the leafy green vegetables. A mere half cup of cooked collard greens provides 440 micrograms, but if you're not into collard greens, the same amount of spinach offers 360 micrograms. Brussels sprouts have about half that much, and broccoli and cabbage offer 113 and 75 mcg respectively. (A half cup serving is four Brussels sprouts, five broccoli florets, and six forkfuls of spinach.)
If you're taking the anticoagulant Coumadin, however, increasing your intake of vitamin K (which is a coagulant) could offset some of the benefit of the Coumadin--in which case your doctor may have to adjust your dose of Coumadin. (It is for this reason that vitamin-mineral products for seniors--Centrum Silver, for example--contain as little as a mere 10 mcg of vitamin K. So don't count on getting your vitamin K from such a supplement.)
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|Date:||Jan 1, 1998|
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