Vitamin D intake is inversely associated with rheumatoid arthritis: results from the Iowa Women's Health Study

Arthritis Rheum. 2004 Jan;50(1):72-7. doi: 10.1002/art.11434.

Abstract

Objective: Vitamin D is a potent regulator of calcium homeostasis and may have immunomodulatory effects. The influence of vitamin D on human autoimmune disease has not been well defined. The purpose of this study was to evaluate the association of dietary and supplemental vitamin D intake with rheumatoid arthritis (RA) incidence.

Methods: We analyzed data from a prospective cohort study of 29,368 women of ages 55-69 years without a history of RA at study baseline in 1986. Diet was ascertained using a self-administered, 127-item validated food frequency questionnaire that included supplemental vitamin D use. Risk ratios (RRs) and 95% confidence intervals (95% CIs) were estimated using Cox proportional hazards regression, adjusting for potential confounders.

Results: Through 11 years of followup, 152 cases of RA were validated against medical records. Greater intake (highest versus lowest tertile) of vitamin D was inversely associated with risk of RA (RR 0.67, 95% CI 0.44-1.00, P for trend = 0.05). Inverse associations were apparent for both dietary (RR 0.72, 95% CI 0.46-1.14, P for trend = 0.16) and supplemental (RR 0.66, 95% CI 0.43-1.00, P for trend = 0.03) vitamin D. No individual food item high in vitamin D content and/or calcium was strongly associated with RA risk, but a composite measure of milk products was suggestive of an inverse association with risk of RA (RR 0.66, 95% CI 0.42-1.01, P for trend = 0.06).

Conclusion: Greater intake of vitamin D may be associated with a lower risk of RA in older women, although this finding is hypothesis generating.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Arthritis, Rheumatoid / epidemiology*
  • Arthritis, Rheumatoid / prevention & control
  • Calcium, Dietary / administration & dosage
  • Female
  • Follow-Up Studies
  • Humans
  • Incidence
  • Middle Aged
  • Prospective Studies
  • Risk Factors
  • Surveys and Questionnaires
  • Vitamin D / administration & dosage*

Substances

  • Calcium, Dietary
  • Vitamin D