Reduced vitamin D intake has been linked to increased risk of developing RA and vitamin D deficiency has been found to be associated with disease activity and musculoskeletal pain in patients with RA. In a recent study, researchers evaluated vitamin D status in 44 patients with RA and looked for any relationship between vitamin D serum levels and disease activity. A control group of 44 persons was evaluated as well.
Vitamin D circulates in the body in two forms. The liver converts
vitamin D to 25-hydroxyvitamin D3 [25(OH)D3], also known as calcidiol.
The kidneys convert calcidiol to activated vitamin D, also known as
1,25-dihydroxyvitamin D [1,25(OH)2D] or calcitriol. When measuring
vitamin D levels in the blood, the recommended test measures serum
concentration of 25(OH)D3, reported as nanomoles per liter (nmol/L)
and/or nanograms per milliter (ng/mL).
Persons who have serum concentrations of 25(OH)D3 less than 12 ng/mL
are considered deficient in vitamin D. Levels between 12 and 20 ng/mL
are considered inadequate in healthy persons. Greater than 20 ng/mL is
considered adequate in healthy persons. According to NIH, levels
greater than 50 ng/mL may cause undesirable adverse effects. However,
some rheumatologists (including my own) recommend serum concentrations
between 50-80 ng/mL in patients diagnosed with autoimmune disease.
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Vitamin D Deficiency Associated with Disease Activity in RA