Protein, iron, and meat consumption and risk for rheumatoid arthritis: a prospective cohort study

E Benito-Garcia,Lisa A Mandl,Frank B Hu,Diane Feskanich,Elizabeth W Karlson

doi:10.1186/ar2123

Abstract

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.

Highlights

Rheumatoid arthritis (RA) is associated with both genetic and environmental factors [1,2,3,4,5,6,7], but studies of dietary risk factors have been inconclusive [8]
A recent prospective study showed that higher consumption of red meat and total protein was associated with increased risk for inflammatory polyarthritis
We prospectively examined the relationship between diet and incident rheumatoid arthritis (RA) among 82,063 women in the Nurses' Health Study

Summary

Introduction

Rheumatoid arthritis (RA) is associated with both genetic and environmental factors [1,2,3,4,5,6,7], but studies of dietary risk factors have been inconclusive [8]. Studies of diet and risk for RA offer the potential to identify modifiable factors and so prevent RA in high-risk patients; they may provide insights into disease pathogenesis. The prevalence of RA is higher in countries with greater consumption of red meat [14]. Pattison and colleagues [15] reported the first prospective investigation of red meat and risk for inflammatory polyarthritis (IP) and concluded that higher intakes of both red meat and protein increased the risk for IP, whereas iron – another nutrient component of meat – exhibited no association. The authors acknowledged that it remained unclear whether the observed associations were causative or whether meat consumption was a marker for other lifestyle factors

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