Protein, iron, and meat consumption and risk for rheumatoid arthritis: a prospective cohort study
1 Section of Clinical Sciences, Division of Rheumatology, Immunology and Allergy, Department of Medicine, Brigham & Women's Hospital, Francis Street, Boston, Massachusetts 02115, USA
2 BioEPI Clinical and Translational Research Center, Taguspark, Núcleo Central,232 2740-122 Oeiras, Portugal
3 Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Longwood Avenue, Boston, Massachusetts 02115, USA
4 Department of Nutrition, Harvard School of Public Health, Huntington Avenue, Boston, Massachusetts 02215, USA
5 Rheumatology Clinical Research Center, Hospital for Special Surgery, East 70th Street, New York, New York 10021, USA
Arthritis Research & Therapy 2007, 9:R16 doi:10.1186/ar2123Published: 8 February 2007
A recent prospective study showed that higher consumption of red meat and total protein was associated with increased risk for inflammatory polyarthritis. We therefore prospectively examined the relationship between diet (in particular, protein, iron, and corresponding food sources) and incident rheumatoid arthritis (RA) among 82,063 women in the Nurses' Health Study. From 1980 to 2002, 546 incident cases of RA were confirmed by a connective tissue disease screening questionnaire and medical record review for American College of Rheumatology criteria for RA. Diet was assessed at baseline in 1980 and five additional times during follow up. We conducted Cox proportional hazards analyses to calculate the rate ratio of RA associated with intakes of protein (total, animal, and vegetable) and iron (total, dietary, from supplements, and heme iron) and their primary food sources, adjusting for age, smoking, body mass index, and reproductive factors. The multivariate models revealed no association between RA and any measure of protein or iron intake. In comparisons of highest with lowest quintiles of intake, the rate ratio for total protein was 1.17 (95% confidence interval 0.89–1.54; P for trend = 0.11) and for total iron it was 1.04 (95% confidence interval 0.77–1.41; P for trend = 0.82). Red meat, poultry, and fish were also not associated with RA risk. We were unable to confirm that there is an association between protein or meat and risk for RA in this large female cohort. Iron was also not associated with RA in this cohort.