Vitamin K Helps Prevent Bone Fractures

There’s More to Vitamin K than Was Thought

Vitamin K Helps
Prevent Bone Fractures

Blood-clotting vitamin protects postmenopausal
women from the most feared consequence of osteoporosis
By Hyla Cass, M.D.

n a speech he gave in the British House of Commons one day in 1933, Winston Churchill was venting his considerable spleen at his political nemesis, former Prime Minister Ramsay MacDonald, who was notoriously soft on the Nazi threat. Churchill said, “I remember, when I was a child, being taken to the celebrated Barnum’s Circus, which contained an exhibition of freaks and monstrosities. But the exhibit on the program which I most desired to see was the one described as ‘The Boneless Wonder.’ My parents judged that that spectacle would be too revolting and demoralizing for my youthful eyes, and I have waited fifty years to see The Boneless Wonder sitting on the Treasury Bench.”

No one ever got the better of Churchill in a battle of wits, nor did anyone ever show more backbone in defying a monstrous evil. (What the world needs now, more than ever, is his indomitable spirit and courage. The wit wouldn’t hurt either.)

Churchills we are not, but fortunately for us, neither are we MacDonalds—we do have bones. They keep us from collapsing into a puddle of flesh and blood, they protect our vital organs, and they allow us to run and jump and dance for joy. Unfortunately, however, they sometimes break, especially as we get older and they become less dense and more brittle. In its early stages, this condition is called osteopenia (“diminished bone,” from the Greek osteon, bone, and penia, poverty); its more severe form is called osteoporosis (“porous bone”).

Osteoporosis—A Setup for Bone Fractures

Women (white women most of all) are more susceptible to osteoporosis than men, owing to estrogen loss after menopause. The gender gap for this disease, however, isn’t as great as many people—especially men—seem to think. Men can and do get osteoporosis, a serious disease that typically remains asymptomatic and undetected until a bone breaks, usually from a fall. Nearly all nonvertebral fractures in the elderly are caused by falls, but vertebral fractures often occur without a fall. With hip and spine fractures, the results can be catastrophic in terms of health, and even of life itself.

The main risk factors for osteoporosis are advanced age, family history, unhealthy lifestyle choices (such as smoking, excessive drinking, inadequate exercise, and a low intake of calcium and vitamin D), being overly thin, and, for women, being postmenopausal.* For bone fractures in particular, the main risk factors are advanced age, low bone mineral density, and previous fracture as an adult. Peak bone mass, which is determined mainly by heredity, is achieved during the third decade of life, when the process of bone loss begins. The process accelerates at menopause, and by age 80, many women have lost, on average, about 30% of their peak bone mass.

*Osteoporosis can also be caused or exacerbated by various medications (especially glucocorticoids, such as cortisone), disease states, and genetic disorders.

© Dominick
In the USA, white women are at the greatest risk of osteoporotic fracture: 13–18% of white American women aged 50 or older have osteoporosis of the hip, and another 37–50% have osteopenia of the hip.1 The prevalence increases from 4% in women aged 50–59 to 52% in women aged 80 or older. For a woman of 50, the lifetime risk for an osteoporotic fracture is 40%, and osteoporosis contributes to about 90% of all hip and spine fractures in older women.

Calcium, Vitamin D, & Vitamin K—Good to the Bone

Thus, where bone health is concerned, my advice to older people is: (1) do your best to prevent osteoporosis, and (2) if you have it, try to prevent it from getting worse; also, take extra precautions to avoid falls, because the primary objective of osteoporosis therapy is to prevent fractures. To hold the disease at bay, or to keep it in check if you have it, good diet and regular exercise (and, of course, not smoking and not drinking to excess) are very important, as they are for virtually all the ills that afflict us.

But you knew that. Now let’s talk about supplements that could help. Much has been written about the benefits of taking ample amounts of calcium and vitamin D in order to maintain bone density and, therefore, bone strength. As so often occurs in medicine, however, confusion has recently arisen over results that seem to be in conflict with each other. For more on that, see the sidebar on this subject.

Calcium and Vitamin D—The Rest of the Story

The abstract of a paper published recently in the New England Journal of Medicine stated that in healthy postmenopausal women, supplementation with calcium (1000 mg/day as calcium carbonate) and vitamin D (400 IU/day) provides a small but significant improvement in hip-bone density but does not provide significant protection against hip fracture.1 The latter got the media’s attention, and it was widely reported.

But what is “the rest of the story,” as Paul Harvey likes to say? First of all, the incidence of hip fracture in this massive study (36,282 women, aged 50–79, who were followed for 7 years) was reduced by 12%. This was found not to be a statistically significant decrease, however, per the criteria used for evaluating the data.

But there was a significant catch: the data analysis included even those women who had not adhered to the required supplementation regimen, and the authors admitted that “It is also plausible that there was a benefit only among the women who adhered to the study treatment.” Indeed, when they adjusted the analysis to exclude the data for the noncompliers, they found that there was

. . . a significant, 29% relative decrease—a finding consistent with the results of other trials that showed that efficacy in fracture reduction is enhanced among women adherent to calcium with vitamin D supplementation or is present only in this group.

Even when the noncompliers were left in, an age-adjusted analysis showed that the older, more vulnerable women (70–79) showed an 18% reduction in the risk for hip fracture. Somehow, these aspects of the story were not reported by the media—nor were various other factors (discussed candidly by the authors) that may have skewed the overall analysis toward the somewhat misleading results that were reported. As I constantly remind my patients and readers, don’t take media reports on supplements at face value. Check out reliable sources (such as this magazine) for a broader perspective and more accurate interpretation.

Meanwhile, the North American Menopause Society (NAMS) has recently published its “2006 Position Statement” on the management of osteoporosis in postmenopausal women. It contains the following statements:2

Low vitamin D intake has been linked to impaired muscle strength, increased fall risk, and increased fracture risk along with increased rates of bone loss. Furthermore, treatment with vitamin D has been found to reduce fracture risk in elderly postmenopausal women, although not in all studies. Elderly postmenopausal women have an increased risk of hip fracture associated with low dietary calcium intake. …

In general, postmenopausal women in the United States and Canada have dietary calcium intakes that are low, with median intakes of approximately 600 mg/day. … most women need an additional 600 to 900 mg/day (two to three dairy portions) over their usual daily intake to reach recommended levels. . . . The nutrient vitamin D is essential for the intestinal absorption of calcium. … NAMS recommends intake of 700 to 800 IU/day for women at risk of deficiency because of inadequate sunlight exposure, such as older, frail, chronically ill, housebound, or institutionalized women or those who live in northern latitudes.


  1. Jackson RD, LaCroix AZ, Gass M, et al., for the Women’s Health Initiative Investigators. New Engl J Med 2006 Feb16;354:669-83.
  2. Anon. Management of osteoporosis in postmenopausal women: 2006 position statement of the North American Menopause Society. Menopause 2006;13:340-67.

Here we will focus on a more obscure nutrient that can also be beneficial for bone health: vitamin K (for which the other sidebar offers a primer). It has been known for several years that there are at least three vitamin K-dependent proteins (osteocalcin, MGP, and protein S) present in bone and cartilage, and interest in vitamin K’s effects on these proteins and on bone metabolism has been growing.

A Vitamin K Primer

We hear a lot about the benefits of taking vitamins A, C, D, E, and the B-complex, which consists of eight different vitamins. That’s 12 altogether. But what about the 13th vitamin, the last of the lot, called K? How come we never hear about that one? The answer is that vitamin K deficiencies are rare in healthy adults, because it’s so abundant in our food. (Although it’s fat-soluble, our bodies store very little of it, so it would be rapidly depleted without our daily food intake.)

So we don’t worry about vitamin K. Nonetheless, we should take a greater interest in this forlorn vitamin, because recent discoveries suggest that it may play a more important role in our health—especially that of our bones—than was previously thought. That aspect of vitamin K is covered in the article. Here we’ll review the basics.

Vitamin K (from the German Koagulation) is essential for blood coagulation (clotting), i.e., it prevents hemorrhaging. If our blood didn’t clot at appropriate times and places, we would bleed to death. One might think that vitamin K would be helpful in treating hemophilia, but unfortunately it’s not. It is, however, widely used to minimize bleeding during and after surgical operations.

Vitamin K exists in two main forms, called K1 and K2, neither of which has any known toxicity associated with it. Vitamin K1 is a yellow, viscous oil found in plants—mainly leafy green vegetables—and vegetable oils. For commercial use, it’s extracted from alfalfa or made synthetically. Its scientific name is phylloquinone, but it’s also called phytonadione or phytomenadione.

Vitamin K2 is a class of five related crystalline compounds that are collectively called menaquinone, with variations on that name for the individual compounds. Vitamin K2 is found in various intestinal bacteria, and it’s isolated mainly from hog livers and putrefied fish meal.* In our own bodies, it’s found in high concentrations in our large intestines, a place not generally thought of as harboring anything very useful or healthful. It’s also found abundantly in the liver, and it circulates in the blood.

*You read that right—but don’t be dismayed. Extracting beneficial compounds from disgusting sources is commonplace, because unwanted substances can be removed through modern chemical purification techniques. Astronauts drink water—purer than any tap water—recycled from their own bodily wastes.

Our bodies use vitamin K in the synthesis of certain proteins that are critical to the blood-clotting process. This is a complex cascade of calcium-ion-dependent biochemical reactions whose end result is the formation of a fibrous web consisting of an elastic, insoluble protein called fibrin. As blood cells and platelets become enmeshed in the fibrin web, a gelatinous mass called a thrombus, or blood clot, is formed. The reaction cascade has built-in control mechanisms that normally prevent excessive clotting, which can be as life-threatening as excessive bleeding, especially if clots form in the coronary arteries or the brain.

Sometimes, however, those mechanisms are inadequate, and patients who are at risk for clotting are given an oral anticoagulant, such as warfarin (Coumadin®), which inhibits the action of vitamin K. Such patients should be careful not to take too much vitamin K, lest in override that inhibitory action and defeat the purpose of the therapy.

Researchers Look at Vitamin K . . .

A team of researchers in England recently undertook a meta-analysis of the scientific literature on vitamin K as it pertains to bone fracture.2 In a meta-analysis, experts in a given subject pool the data from carefully selected, published studies of a similar nature, correct them mathematically for potentially confounding factors, and subject them to rigorous statistical analyses so as to reach conclusions of greater significance than would be possible from any individual study.

In the present case, the researchers combed the international literature, identified 352 potentially relevant articles, and narrowed them down to a final seven that met their criteria: they had to be randomized clinical trials involving adults who were given supplemental vitamin K (any dose) for at least 6 months, and the measured outcome had to be bone fractures of any type. [The only synthetic forms of vitamin K that are available for use as supplements are K1 (phylloquinone) and one member of the K2 family, namely, menaquinone-4, aka menatetrenone.]

The researchers also evaluated (but not by meta-analysis) six other trials that measured changes in bone mineral density (BMD) but that did not involve fractures. Altogether, the 13 trials involved nearly 1400 patients, the great majority of whom were postmenopausal women. The researchers stated that the quality of many of the 13 trials they accepted was “not high” (a common problem in clinical trials). They cited a variety of other potential weaknesses that could have skewed the results—including the fact that all seven of the trials in the fracture meta-analysis had been done in Japan, whose population may not be broadly representative in this regard.

. . . And Find Striking Evidence of Bone Benefits

The idea of a meta-analysis, however, is to do the best one can with what’s available, and the results here were positive: supplementation with vitamin K—especially the K2 form menaquinone-4, which was used in 11 of the 13 trials—was associated with increased BMD and reduced fracture incidence.* The latter data were particularly striking: with menaquinone-4 (used in all seven fracture trials), the risks for vertebral fractures, hip fractures, and all nonvertebral fractures were reduced by 60%, 77%, and 81%, respectively. In the trials that measured BMD, all but one showed improvement with the use of vitamin K. (The dosage in 10 of the 11 trials using menaquinone-4 was 45 mg/day.)

*Menaquinone-4 is not found in significant amounts in food, but it can be bacterially synthesized in small amounts from vitamin K1 in our colon (a process that can be impaired by the long-term use of broad-spectrum antibiotics, which kill the bacteria). Whether it’s more effective than vitamin K1 against osteoporosis is not known.

Look at Your Bones, and Wonder

The results of the British study suggest that vitamin K plays a hitherto greatly underappreciated role in bone metabolism. It may also have some more surprises up its sleeve, in terms of physiological functions that we don’t yet know much about. There is, e.g., a vitamin K-dependent protein, Gas6, that has been found throughout the nervous system as well as in the heart, lungs, stomach, kidneys, and cartilage.3 It appears to be a growth factor, which implies that vitamin K is involved in a growth mechanism.

As we grow older, it behooves us all to “look inside” ourselves and make sure we’re taking good care of everything we’re made of so that it doesn’t break—starting with our bodies’ most basic structural elements, our bones.


  1. Anon. Management of osteoporosis in postmenopausal women: 2006 position statement of the North American Menopause Society. Menopause 2006;13:340-67.
  2. Cockayne S, Adamson J, Lanham-New S, Shearer MJ, Gilbody S, Torgerson DJ. Vitamin K and the prevention of fractures. Arch Intern Med 2006;166:1256-61.
  3. Higdon J. Vitamin K. Linus Pauling Institute, Corvallis, OR, 2004.

Dr. Hyla Cass is a nationally recognized expert in integrative medicine, an assistant clinical professor of psychiatry at the UCLA School of Medicine, and the author or coauthor of several popular books, including Natural Highs: Supplements, Nutrition, and Mind-Body Techniques to Help You Feel Good All the Time and 8 Weeks to Vibrant Health: A Woman’s Take-Charge Program to Correct Imbalances, Reclaim Energy, and Restore Well-Being.

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