Higher intake of vitamin K, found naturally in cabbage, spinach, cauliflower, and other green leafy vegetables, could reduce the risk of osteoarthritic knee problems by 40 percent, says new research.
Other epidemiological studies have shown a correlation between high vitamin K intake and a lower incidence of osteoporosis. One European study also showed that a combination of vitamins K and D, along with calcium, could have a significant effect on improving bone strength. The new study, published in the journal Arthritis and Rheumatism, is another observational study of the benefits of the fat-soluble vitamin on bone health.
Tuhina Neogi from the Boston University School of Medicine led the population-based prospective cohort. Poor intake of vitamin K is common, as would be suspected based the standard American diet (SAD) and the vegetables that contain the highest vitamin K concentrations. Insufficient vitamin K can result in abnormal cartilage and bone mineralization. The researchers found a correlation between the highest and lowest vitamin K intakes, and the respective risks of hand and knee osteoarthritis among 672 participants, with an average age of 66.
The researchers measured blood levels of phylloquinone, the main form of vitamin K, and correlated this with the occurrence of hand and knee osteoarthritis, recorded by radiographs. “As plasma phylloquinone levels rose, the prevalence ration (PR) for hand osteoarthritis decreased from 1.0 to 0.7,” reported Neogi.
“For the knee, only the PR for osteophytes [outgrowths on the bone associated with arthritis] and the adjusted mean number of knee joints with osteophytes decreased significantly with increasing plasma phylloquinone levels,” she said.
The researchers concluded that their data support the link between vitamin K status and the risk of osteoarthritis, a disease that effects about seven million people in the UK alone are reported to have long-term health problems associated with arthritis. Around 206m working days were lost in the UK in 1999-2000, equal to £18bn (€26bn) of lost productivity.
Further study is clearly need to establish if the relationship is causal, particularly clinical trials - and indeed, some are already underway.
According to Controlled Clinical Trials, there are 12 registered clinical trials at various stages of completion being conducted worldwide using vitamin K. Six are concerned with bone health, while a further four are associated with the role of the vitamin in blood clotting.
OBJECTIVE: Poor intake of vitamin K is common. Insufficient vitamin K can result in abnormal cartilage and bone mineralization. Furthermore, osteophyte growth, seen in osteoarthritis (OA), may be a vitamin K-dependent process. We undertook this study to determine whether vitamin K deficiency is associated with radiographic features of OA. METHODS: We conducted an analysis among 672 participants (mean age 65.6 years, 358 women) in the Framingham Offspring Study, a population-based prospective observational cohort. Levels of plasma phylloquinone (the primary form of vitamin K) had previously been measured in these participants, for whom we also had bilateral hand and knee radiographs. The main outcomes were 1) prevalence ratios (PRs) of OA, osteophytes, and joint space narrowing (JSN) per quartile of plasma phylloquinone level for each joint, adjusting for correlated joints using generalized estimating equations, and 2) adjusted mean number of joints with each feature per quartile of plasma phylloquinone level. Analyses were conducted in hands and knees separately and adjusted for age, sex, body mass index, total energy intake, plasma vitamin D, and femoral neck bone mineral density. RESULTS: The PRs for OA, osteophytes, and JSN and adjusted mean number of joints with all 3 features in the hand decreased significantly with increasing plasma phylloquinone levels (P </= 0.03 for all). For example, as plasma phylloquinone levels rose, the PR for hand OA decreased from 1.0 to 0.7 (P = 0.005). For the knee, only the PR for osteophytes and the adjusted mean number of knee joints with osteophytes decreased significantly with increasing plasma phylloquinone levels (PR decreased from 1.0 to 0.6, P = 0.01). CONCLUSION: These observational data support the hypothesis of an association between low plasma levels of vitamin K and increased prevalence of OA manifestations in the hand and knee.
Neogi T, Booth SL, Zhang YQ, Jacques PF, Terkeltaub R, Aliabadi P, Felson DT. Low vitamin K status is associated with osteoarthritis in the hand and knee. Arthritis Rheum. 2006 Mar 29;54(4):1255-1261 [Epub ahead of print].