Vitamin K may be the answer to one of the most vexing problems of aging. The older a person gets, the more likely it is that their blood vessels will harden up at the same time their bones go soft. Does one have to do with the other? The answer is yes. They both share a common underlying mechanism that controls calcium. And that mechanism depends on the vitamin known as vitamin K. Vitamin K has special powers over calcium, a mineral that leaves bones and builds up in arteries with age.
Researchers have discovered over a hundred special proteins in the body that chaperone calcium. Vitamin K makes them all tick by enabling them to latch onto the mineral. Once they’ve gotten ahold of it, they either escort it out, or, in the case of bone, deposit it like mortar. Arteries want calcium out: bones want it in. Osteocalcin is the most famous vitamin K protein. It chaperones calcium into bone. But there are other less known proteins that take calcium out of soft tissue like arteries. The one thing they all have in common is vitamin K. They must be activated by K to work.
Studies are beginning to show just how important vitamin K is for maintaining these proteins. Researchers looking at data from 72,327 nurses have reported that people getting the most vitamin K have a 30% lower risk of hip fracture than those getting the least. Other studies back up this data for other parts of the skeleton. Despite the need for vitamin K, researchers at Tufts University say the RDA for vitamin K is not even in the ballpark. Currently set at 1 microgram per kilogram of body weight (about 65 micrograms for a 140 pound woman), the RDA falls way short of the 45 milligrams necessary to stop bone loss in adult women.
Even higher doses may be necessary to keep calcium out of arteries. Researchers in Japan had to use high doses of vitamins K and E to keep rats from getting heart disease. Their research follows years of scientific argument that hypertension, which often precedes heart attack and stroke, is essentially a calcium problem that can be treated with vitamin K.
Although vitamin K is fat-soluble, it is the only such vitamin the body doesn’t store. The body recycles it, but according to some research, drugs interfere, and gut flora doesn’t contribute as much as previously thought.
Feskanich D, et al. 1999. Vitamin K intake and hip fractures in women: a prospective study. Am J Clin Nutr 69:74-9. Booth SL, et al. 1998. Dietary intake and adequacy of vitamin K1. J Nutr 128:785-88