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

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.

Antioxidant micronutrients and risk of rheumatoid arthritis in a cohort of older women.

The association of antioxidant vitamins and trace elements from foods and supplements with risk of rheumatoid arthritis was evaluated in a prospective cohort study of 29,368 women who were aged 55-69 years at baseline in 1986. Through 1997, 152 cases of rheumatoid arthritis were identified. After controlling for other risk factors, greater intakes (highest tertile vs. lowest) of supplemental vitamin C (relative risk (RR) = 0.70, 95% confidence interval (CI): 0.48, 1.09; p-trend = 0.08) and supplemental vitamin E (RR = 0.72, 95% CI: 0.47, 1.12; p-trend = 0.06) were inversely associated with rheumatoid arthritis. There was no association with total carotenoids, alpha- or beta-carotene, lycopene, or lutein/zeaxanthin, while there was an inverse association with beta-cryptoxanthin (RR = 0.59, 95% CI: 0.39, 0.90; p-trend = 0.01). Greater use of supplemental zinc (RR = 0.39, 95% CI: 0.17, 0.88; p-trend = 0.03) was inversely associated with rheumatoid arthritis, while any use of supplemental copper (RR = 0.54, 95% CI: 0.28, 1.03) and manganese (RR = 0.50, 95% CI: 0.23, 1.07) showed suggestive inverse associations with rheumatoid arthritis. Greater intakes of fruit (RR = 0.72, 95% CI: 0.46, 1.12; p-trend = 0.13) and cruciferous vegetables (RR = 0.65, 95% CI: 0.42, 1.01; p-trend = 0.07) also exhibited trends toward inverse associations with risk. When the antioxidants were modeled together, only beta-cryptoxanthin and supplemental zinc were statistically significant predictors. Intake of certain antioxidant micronutrients, particularly beta-cryptoxanthin and supplemental zinc, and possibly diets high in fruits and cruciferous vegetables, may be protective against the development of rheumatoid arthritis.

Coffee, tea, and caffeine consumption and risk of rheumatoid arthritis: results from the Iowa Women's Health Study.

OBJECTIVE: To evaluate whether coffee, tea, and caffeine consumption are risk factors for rheumatoid arthritis (RA) onset among older women. METHODS: These factors were evaluated in a prospective cohort study that was initiated in 1986 and that included 31,336 women ages 55-69 years without a history of RA. Risk factor data were self-reported using a mailed questionnaire. Through 1997, 158 cases of RA were identified and validated against medical records. The relative risk (RR) and 95% confidence interval (95% CI) were used as the measures of association and were adjusted for age, alcohol use, smoking history, age at menopause, marital status, and the use of hormone replacement therapy. RESULTS: Compared with those reporting no use, subjects drinking > or =4 cups/day of decaffeinated coffee were at increased risk of RA (RR 2.58, 95% CI 1.63-4.06). In contrast, women consuming >3 cups/day of tea displayed a decreased risk of RA (RR 0.39, 95% CI 0.16-0.97) compared with women who never drank tea. Caffeinated coffee and daily caffeine intake were not associated with the development of RA. Multivariable adjustment for a number of potential confounders did not alter these results. The associations of RA onset with the highest categories of decaffeinated coffee consumption (RR 3.10, 95% CI 1.75-5.48) and tea consumption (RR 0.24, 95% CI 0.06-0.98) were stronger in women with seropositive disease compared with those with seronegative disease (RR 1.54, 95% CI 0.62-3.84 and RR 0.93, 95% CI 0.27-3.20, respectively). CONCLUSION: Decaffeinated coffee intake is independently and positively associated with RA onset, while tea consumption shows an inverse association with disease onset. Further investigations of decaffeinated coffee and tea intake as arthritis risk factors are needed to verify these findings and explore their biologic basis.