The Better Bones Blog

by Dr. Susan Brown, PhD.

High-dose vitamin K: New-found protection from bone fracture and cancer?

In September of 2008, I attended the large American Society for Bone Mineral Research Meeting held in Montreal, Canada. Generally these meetings are dominated by pharmacological approaches to bone health, but, looking at the big book schedule of lectures, I was delighted to find an entire session on vitamin K.

In this session, several of the top vitamin K researchers reported with disappointment their findings that vitamin K did not seem to improve bone density. I was not too upset by this finding, and really did not expect vitamin K to increase bone density much. Previously, French researchers and others had already noted that higher vitamin K status was inversely correlated with fracture incidence independent of bone density. What I did not expect, however, were the astonishing findings regarding dramatic reductions in both fracture and cancer in postmenopausal women given daily 5 mg of vitamin K1 over 2 to 4 years. The placebo-controlled study, known as the ECKO trial, was conducted by researchers from the University of Toronto, and involved 440 postmenopausal women with osteopenia.

The primary goal, or endpoint, of the study was to see if high dose vitamin K1 (5 mg/day) would increase bone density. The secondary endpoint included changes in bone turnover markers, height, fractures, adverse effects, and health related quality of life. While the study showed no significant changes in bone density over the 2-4 year period, fewer women in the vitamin K group had clinical fractures (9 as compared to 20, a 55% reduction in fractures) and fewer had cancers (3 as compared to 12, a 75% reduction in cancers). Although the study was not designed to test the ability of high dose vitamin K to reduce fractures and cancer, the findings certainly suggest this is a strong possibility.

Years ago at the Center for Better Bones, we identified vitamin D and vitamin K as the two most promising, yet most understudied, bone-building nutrients. The vitamin D story has exploded, as you probably know, and I am sure this remarkable vitamin K1 study and the growing documentation on vitamin K2 in the form of MK-7 are now fueling a vitamin K revolution.

 

Reference:

Cheung, Angela, et al. 2008. Vitamin K supplementation in postmenopausal women with osteopenia (ECKO Trial): A randomized controlled trial, PLoS Medicine, 5(10):1461-1472.

How to tell if you are losing bone without a bone density test

While most doctors tend to monitor bone density with the dual-energy x-ray absorptiomentry (DEXA) test, there is another, less expensive test helpful in determining if you are currently losing bone. This test, called the cross-linked N-teleopeptide (or NTx for short), is a simple urine or blood test known as a “marker of bone resorption.” When you lose bone, small fragments of bone protein show up in the urine and blood, and measuring these bone protein fragments gives an indication of rate of bone breakdown. In most cases a high rate of bone breakdown, also known as bone resorption, indicates that there is an ongoing loss of bone mass.

The bone resorption markers most commonly used are the urine NTx osteomark marker and the urine deoxypyridinium cross-links (Dpd). Your physician can order either of these tests. Generally, a score that’s near or even a bit below the premenopausal mean for women, and one near or even a bit below the young adult mean for men, is ideal. In both tests, the higher the number, the greater the likelihood of a more rapid rate of ongoing bone loss. For more details see my articles on bone density testing and bone resorption testing.

 

How accurate is a DEXA bone density test?

Nearly every day I see women and physicians themselves getting very worried when a woman’s bone density tests show even a small 1-2% decline. Women are often told their fracture risk has greatly increased and that they should immediately begin osteoporosis drug therapy. For many women, the growing “osteoporosis fear” is fueled by small reductions in bone density. But what do these small changes really mean, and just how accurate are the DEXA bone density tests anyway?

Thanks to the excellent work of the University of Washington osteoporosis specialist, Dr. Susan Ott, we now know that the common bone density test is rather imprecise and large changes in density are needed to assure that bone loss is indeed occurring, much less significant in nature. A thoughtful scientist, Dr. Ott had 300 patients get two bone density measurements: one when they came into the room, and the second after walking around the room for a while. With this simple experiment she showed that repeat measurements on the same day may show as much as 7% difference in bone mineral density. Breaking down the data she found that while a 4-6% change in bone mineral density indicates a “probably change” it takes more than a 6% change to fully guarantee a statistically significant change in bone density.

The Better Bones perspective on bone density testing: Bone density testing can be useful, especially when spaced over many years, but small changes are not significant and certainly not a basis for beginning bone drug therapy.

 

Reference:

Dr. Susan Ott’s website: http://courses.washington.edu/bonephys/opBMDp.html

 


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