Vitamin K is a fat-soluble nutrient that appears to have a role in OA (Shea 2014). In normal healthy adults, adequate daily intake is only 120 micrograms for men and 90 micrograms for women. Yet vitamin K insufficiency or deficiency is quite common in western populations:

• 8-31% of normal healthy adults have vitamin K deficiency/insufficiency
• ~50% in people suffering hypertension, type 2 diabetes and cardiovascular or chronic Kidney disease
• 97% of older subjects in a mixed population taking warfarin were also found deficient

A recent publication investigated progression of knee osteoarthritis using MRI. They found significant associations between the level of vitamin K a person has in their system and markers of knee osteoarthritis. For example, the study found that people:

1. with very low blood vitamin K were nearly
   1. twice as likely to have articular cartilage damage &
   2. just under 3 times as likely to have meniscus damage progression after 3 years

compared to people with sufficient vitamin K

1. with higher blood levels of “(dp)ucMGP”, a protein whose concentration reflects lower vitamin K status, had higher odds of:
   1. meniscus damage,
   2. osteophytes,
   3. bone marrow lesions,
   4. subarticular cysts

1. with very low blood vitamin K levels were more likely to have worsening of articular cartilage and meniscus damage

Science has shown that osteoarthritis is a disease not just of cartilage but also of the underlying bone, and that several different vitamin K-dependant proteins are present in both cartilage and in bone. These proteins have weird and wonderful names such as:

1. MGP (matrix Gla protein)
2. GAS-6 (growth-arrest specific gene 6),
3. TGFBI (transforming growth factor β-induced protein ig-h3)
4. PN or OSF-2 (Periostin, or osteoblast specific factor 2)
5. GRP (Gla-rich protein)
6. BGP or OC (bone gamma-carboxyglutamic acid-containing protein or osteocalcin)

All are made by the cells in bone & cartilage. Each protein has various functions in keeping bone and cartilage strong & healthy. The last step in the production processes of all these proteins requires vitamin K. If Vitamin K is low, each of the proteins are still made (except for the last step), so most don’t function. Thus bone & cartilage maintenance suffers, resulting in increased risk of OA over time.

For example, fully functional MGP’s job in cartilage is to inhibit deposition of calcium. In osteoarthritic joints most of the MGP is non-functional (the last production step has been missed). In healthy cartilage MGP is fully functional. So, in healthy cartilage we generally don’t find the bony outgrowths called osteophytes that are typical in osteoarthritic joints!

So, why is vitamin K deficiency so common?

• western diets typically contain foods that are poor sources of vitamin K,
• the vitamin is difficult to absorb from our typical vitamin K rich foods such as spinach,
• We eat few truly fermented foods such as Natto where vitamin K is high and absorbable
• chronic diseases of the gastrointestinal tract are common & decrease absorption
• medicaments such as warfarin significantly lower vitamin K levels

 

Article Written + Submitted by:

Andreas Klein Nutritionist + Remedial Therapist from Beautiful Health + Wellness
P: 0418 166 269