Specific dietary micronutrients are causally associated with arthritis subtypes - Results from the NHANES 2015-2018 and Mendelian randomization study.

Background: micronutrients (MNs) in the diet are linked to arthritis, but the causal relationships and dose-dependent effects remain unclear. Methods: using the National Health and Nutrition Examination Survey (NHANES) and genome-wide association studies (GWAS) databases, multivariate logistic regression, restricted cubic splines (RCS), and Mendelian randomization (MR) were applied to analyze MNs' impact on arthritis. Results: multivariate logistic regression identified six MNs significantly associated with arthritis: calcium (OR = 0.74 [95 % CI, 0.60, 0.92] p = 0.013), magnesium (OR = 0.74 [95 % CI, 0.62, 0.89] p = 0.003), selenium (OR = 0.62 [95 % CI, 0.50, 0.76] p = 0.0001), folic acid (OR = 0.76 [95 % CI, 0.61, 0.94] p = 0.018), vitamin E (OR = 0.77 [95 % CI, 0.64, 0.92] p = 0.01), vitamin B6 (OR = 0.64 [95 % CI, 0.53, 0.78] p = 0.0001). RCS analysis revealed significant non-linear relationships for vitamin B6, vitamin E, folic acid, and selenium (p < 0.05). MR analysis only confirmed causal associations in specific MNs and subtypes of arthritis: calcium and rheumatoid arthritis (OR = 0.648 [95 % CI, 0.436, 0.962] p = 0.031), vitamin B12 and monoarthritis (OR = 2.876 [95 % CI, 1.240, 6.667] p = 0.014), potassium and pyogenic arthritis (OR = 2.124 [95 % CI, 1.003, 4.497] p = 0.049), vitamin B6 and pyogenic arthritis (OR = 1.744 [95 % CI, 1.034, 2.940] p = 0.037), vitamin B12 and other arthritis (OR = 1.414 [95 % CI, 1.035, 1.932] p = 0.03). Conclusions: this study reveals the causal relationship between specific MNs and certain arthritis subtypes, while also observing dose-dependent associations between other MNs and arthritis. These findings provide valuable insights for dietary interventions and preventive strategies targeting arthritis.