Higher vitamin K intake correlated with reduced osteoarthritis knee pain
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In a study spanning 24 months, higher levels of vitamin K intake appeared to correspond with decreased knee symptoms in patients with osteoarthritis, according to data published in Arthritis Care & Research.
“To date there is no study examining if vitamin K intake is associated with reduced knee OA symptoms,” Zetao Liao, MD, of the rheumatology and immunology division of the third affiliated hospital of Sun Yat-Sen University, in Guangzhou, China, and co-authors wrote. “Therefore, the evidence for the relationship between vitamin K and knee OA is still insufficient.”
To investigate the associations between vitamin K intake and symptom and MRI structural changes in patients with knee OA, Liao and colleagues analyzed participants aged 50 to 79 years from the VIDEO study for 2 years. To be eligible for inclusion, participants were required to have symptomatic OA for at least 6 months, have knee pain between 20 mm and 80 mm on a 100 mm visual analogue scale, and demonstrate serum 25-hydroxyvitamin D levels ranging from 12.5 nmol per liter to 60 nmol per liter.
Participants completed questionnaires detailing knee symptoms at baseline and at every visit for 24 months. Symptoms were measured by way of the Western Ontario and McMaster University Osteoarthritis Index (WOMAC). Visual analogue scores of knee pain were also assessed at each visit. Patients were also required to answer a survey measuring their dietary and physical activity habits at baseline. Cartlidge defects, bone marrow lesions and effusion-synovitis volumes were measured through MRI scans.
In all, 212 patients were followed and analyzed for 2 years. According to the researchers, higher vitamin K intake was “significantly associated” with a greater decrease in total WOMAC and dysfunction scores over that time. In addition, patients with severe visual analogue score-measured pain at baseline who consumed higher levels of vitamin K recorded better improvement in WOMAC scores, the authors wrote. There was no significant association between vitamin k intake and MRI feature changes.
In various subgroup analyses, vitamin K intake appeared to be negatively associated with changes in tibiofemoral, patellar and total cartilage defects in patients with severe baseline radiographic grade.
“The association of higher baseline vitamin K intake with decreased knee symptoms over 24 months in patients with knee OA in our study suggests that clinical trials examining the effect of vitamin K supplementation for knee OA symptoms are warranted,” Liao and colleagues wrote. “Whether there is an effect on knee structure is unclear and requires further investigation.”
Perspective
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David A. McLain, MD, MACR, FACP, FRCP
Why vitamin K? Vitamin K dependent proteins have been discovered in several extra-hepatic tissues and have important physiological functions, for example in soft-tissue calcification and bone metabolism. Vitamin K has been implicated in osteoarthritis because vitamin K dependent proteins are found in cartilage and bone.
MGP is among the most studied vitamin K dependent protein expressed in human cartilage. Uncarboxylated MGP (the nonfunctional form) is elevated in human arthritic cartilage, while carboxylated (functional) MGP is more abundant in healthy cartilage. Vitamin K has been implicated in age-related bone loss and studied extensively in that regard. Dietary intake of vitamin K was inversely associated with presence of knee OA and joint space narrowing.
Further studies have shown that low plasma vitamin K1 (phylloquinone) is associated with the increased prevalence of OA in the hand and knees. Longitudinally, adults with low plasma phylloquinone are more likely to have articular and meniscus cartilage damage. Cross sectionally, higher plasma desphospho-uncarboxylated MGP (the plasma level is an inverse biomarker of vitamin K status) was associated with increased odds of OA features, including osteophytes and lesions. There was no association found between circulating MGP and hand OA in another study.
Aging is characterized by a chronic low-grade, pro-inflammatory state. Age related increases in C-reactive protein, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) result in the low-grade inflammation that appears to contribute to the onset and progression of chronic aging diseases, including cardiovascular disease, osteoarthritis and other chronic diseases. In vitro and animal experiments have found vitamin K suppresses production of pro-inflammatory cytokines.
Studies have shown that individuals who increased dietary Vitamin K1 intake had reduced IL-6 and individuals with the highest plasma phylloquinone had lower IL-6 levels. Plasma phylloquinone inversely correlated with grouped inflammatory markers, and CD40 ligand, IAM-1, IL-6, OPG and TNF-α individually. A Mediterranean diet intervention being conducted in Spain found that participants who increased their dietary phylloquinone intake the most had the greatest reductions in IL-6 and TNF-α over 1 year. Vitamin K is an active area of aging research, as noted above. Who knew?
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