Can daily vitamin K keep osteoarthritis (OA) away or at least lessen its severity? That’s a question researchers eventually want to answer.  

So far, the role of vitamin K in joint health looks promising. In studies going back to 2006 researchers supported by the Arthritis Foundation found that adequate vitamin K was associated with less radiographic evidence of OA.

Now a study published in March 2013 in the American Journal of Medicine shows a vitamin K deficiency is associated with the development of knee OA.

What’s Special About K?

Vitamin K is a fat-soluble vitamin found in leafy green vegetables such as broccoli, kale, spinach and lettuces. It is helps the body make proteins that our blood needs to clot. A vitamin K deficiency could lead to abnormal bleeding. The roles of vitamin K in other body processes including bone density are being studied.

While reading about the effects of vitamin K deficiency on blood vessels of lab animals, Boston University researcher Tuhina Neogi, MD, was intrigued by the fact that animals deficient in vitamin K had calcifications in the blood vessels. She was more intrigued by the fact that some of those same animals had identical processes occurring in their joints.

“That got me thinking – could this in any way be related to arthritis?” she says. Some of the biologic processes causing joints abnormalities were similar to what occurs in OA, she said.  With a Career Development Award from the Arthritis Foundation, she sought some answers.

Low Vitamin K Associated With OA

In a 2006 study published in Arthritis & Rheumatism, Dr. Neogi and colleagues analyzed data from 672 participants in the Framingham Offspring Study, an examination of the adult children of the original Framingham Heart Study – a research project to investigate the causes of heart disease founded by Massachusetts’ Framingham Hospital in 1948. Study participants had already had blood tests to measure levels of phylloquinon (the biologic form of vitamin K in our bodies) between 1996 and 1997 as well as hand and knee x-rays between 2002 and 2004.

The researchers found that higher levels of plasma phylloquinon were associated with less hand osteoarthritis and less specific radiographic features of osteoarthritis (those that show up on X-ray), including osteophytes (bone spurs) and joint-space narrowing, an indication of cartilage destruction.

“It seemed that both for the hand and knee having low vitamin K in the blood was associated with higher likelihood of having OA manifestations in the X-rays,” she says.

Studying Vitamin K Supplementation

Spurred by those findings Dr. Neogi applied to the Arthritis Foundation for – and was awarded – an innovative research grant to add hand X-rays to an ongoing trial by another researcher, Sarah Booth, PhD, associate director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. Neogi’s goal was to investigate the association between vitamin K and bone mineral density and vascular calcification.

“The bulk of the work was already done – the people had been recruited, they had been randomized to vitamin K versus placebo, so all we had to do was obtain X-rays at the end of three years of this double-blind randomized trial,”  says Dr. Neogi.

The vitamin K group received 500 micrograms of vitamin K, as part of a multivitamin formulation. The control group received an identical formulation without vitamin K. “In this trial we only obtained hand X-rays because we felt it was the most likely body location to pick up a signal,” says Dr. Neogi. “We believe that knee OA is very mechanically driven so for systemic treatment we thought hand OA was the best place to look.”

At first scientists were discouraged to find that randomization to vitamin K had appeared to have no effect on hand OA. However, when they looked only at people who had insufficient levels of vitamin K at baseline, the effect was significant. “Those who attained sufficient concentrations at follow up actually had almost 50 percent joint space narrowing in their hand joints,” Neogi says.