Understanding How Vitamin K Helps

In another study designed to understand the OA-Vitamin K connection, researchers didn’t looked not at levels of vitamin K itself. Instead, they focused on Matrix Gla Protein (MGP), a vitamin K-dependent protein found in bone and cartilage, says Devyani Misra, MD, who led the study, which was published in the September 2011 Journal of Rheumatology.

“Our hypothesis was that vitamin K is having its effects on osteoarthritis not necessarily because of vitamin K itself, but because of the effect vitamin K has on particular bone and cartilage proteins,” Misra says.

“There are bone and cartilage proteins that rely on vitamin K to be become a functional form,” Neogi adds. “If vitamin K is inadequate these proteins don’t get activated.

The researchers found that overall protein levels don’t seem to be related to having hand OA or not. However, a genetic variation of the protein does appear to be related to osteoarthritis.

“The story is getting more complicated. Maybe it is not just the vitamin K but some genetic susceptibility as well,” says Dr. Neogi

Furthermore, research by a fellow in Dr. Booth’s lab suggests that higher levels of Vitamin K are associated with less inflammation. “So vitamin K may have more effect than just through these vitamin K dependent proteins, maybe it is also working to reduce inflammation.”

Vitamin K and MRI Findings

In that 2013 study in the American Journal of Medicine, researchers used X-ray and magnetic resonance imaging (MRI) to examine the relationship between vitamin K and early osteoarthritic changes in the knee OA. These tools provide more accurate information about specific joint tissues affected,

The study’s 1,180 participants had knee X-rays and MRI scans at baseline and 30 months later. Their plasma phylloquinone was measured at baseline.

“These were people who had pristine X-rays and MRIs at baseline,” says Dr. Neogi “What we were doing was trying to pick up any new radiographic osteoarthritis, any new cartilage abnormalities and any new osteophytes on the MRI that were not there in the beginning.”

And that’s exactly what they found in the participants with subclinical vitamin K deficiency – meaning the levels were low, but not low enough to cause abnormal bleeding. People who with subclinical vitamin D deficiency were at higher risk of developing new osteoarthritis on X-ray 30 months later. They were also at higher risk of developing new cartilage lesions on MRI.

“At this time it is fascinating to be finding the association of vitamin K low levels with new incident osteoarthritis,” says Dr. Misra, who also received Arthritis Foundation funding for her work. “This is sort of confirming prior reports showing an association with osteoarthritis and vitamin intake nutritionally.”

Are K Supplements OK?

Both researchers stop short of recommending vitamin K supplements to stop or lessen the severity of OA. “I think it is very exciting and is going to the basis of future trials, but I don’t think we are ready to start prescribing,” says Dr. Misra. She and Dr. Neogi express a few concerns.

For one, the optimal dose for joint health is not known, says Dr. Neogi. “What we know about vitamin K levels that are needed in the body are  based upon what is needed for these blood coagulation proteins. What is needed for the bone and cartilage proteins might be different.”

Another concern has to do with the effect of vitamin K supplements on blood thinners. For people taking the blood thinner Coumadin, taking a vitamin K supplement could make adjusting their Coumadin dosage difficult, they say.

Finally, says Dr. Neogi, vitamin K may be less effective for people with OA or who are approaching the age where they are likely to develop it – it may be that people will need to start taking vitamin K when they are young to have the greatest effects.

Still, says Dr. Misra, it wouldn’t hurt to speak to your doctor about having blood levels of vitamin K checked and discussing any measures you should take if you are deficient.  “But I think there is no harm in people eating more healthy green vegetables.”