If you follow media coverage of bone health research, you’ve probably heard a lot lately about Vitamin K2. Let’s look at what we know about Vitamin K2 and its effects on bone health, what we don’t know yet, and what it all means for you, the consumer.
Vitamin K has long been known to be important for blood clotting. In fact, its name comes from the German word koagulation. Research has suggested that Vitamin K also plays a key role in controlling bone metabolism because it’s essential for synthesizing osteocalcin, an important protein for maintaining bone strength.
Vitamin K comes in two forms: Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinone). Vitamin K is found in green leafy and cruciferous vegetables such as spinach, kale, broccoli and Brussels sprouts. Vitamin K2 is primarily produced by bacteria in the gut but is found in small amounts in grass-fed meats and dairy products, and in greater amounts in some cheeses and a few fermented foods like natto, a Japanese soybean product.
Vitamin K1 is generally the preferred form of vitamin K because it is less toxic, works faster, is stronger, and works better for certain conditions.
Vitamin K2 appears to protect the bones more than Vitamin K1, but too little of either is bad for the bones. Studies have shown that poor Vitamin K intake is linked to low bone mass, osteoporosis and fracture risk. Women who consumed less than 109 mcg of Vitamin K per day were found to be more likely to break a hip. Low vitamin K intake has also been linked to increased risk of hip fractures in men and women and to low bone density in women.
Adequate daily intake is 120 mcg and 90 mcg for women. People in the West don’t eat as much Vitamin K as they used to, even 50 years ago, so scientists are studying whether higher amounts should be recommended. A study in 2013 found taking 180 mcg daily helped reduce bone loss in healthy women who had been through menopause.
This chart shows how Vitamin K2 directs bone metabolism.
Taking a specific form of vitamin K2 seems to improve bone strength and reduce the risk of fracture in most older women with weak bones. But it doesn’t seem to benefit older women who still have strong bones.
Studies so far have shown mixed results for supplements of Vitamin K1 and Vitamin K2. Some have found improved bone mineral density, a few showed decreased fracture risk, and others found no additional benefit to bone health.
A review of evidence that appeared in the August 2019 issue of Osteoporosis International cast doubt on the effects of Vitamin K supplements.
For post-menopausal or osteoporotic patients, there is no evidence that vitamin K affects bone mineral density or vertebral fractures; it may reduce clinical fractures; however, the evidence is insufficient to confirm this. There are too few trials to draw conclusions for other patient groups.
The U.S. Food and Drug Administration so far has not authorized health claims on labels for products containing Vitamin K2. Until there is more evidence to support taking supplements, focus on getting a balanced diet in order to get the Vitamin K1 and K2 that your bones need.
Because Vitamin K helps the body with blood clotting, it might decrease the effectiveness of anti-coagulant medicines like warfarin (Coumadin®). Furthermore, long-term use of these anti-coagulant medicines is associated with accelerated bone loss and low bone mass.
Read more about bone-healthy nutrients at americanbonehealth.org. Here are two articles to get you started:
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