Study uncovers significant association between cereal fiber intake and reduced rheumatoid arthritis prevalence

By Tarun Sai LomteReviewed by Danielle Ellis, B.Sc.Feb 1 2024

In a recent study published in Scientific Reports, researchers investigated the association between dietary fiber and the risk of rheumatoid arthritis (RA).

Background

RA is a prevalent inflammatory disorder that damages joints and causes functional impairment. The global prevalence of RA has been increasing at 8.2% annually since 1990, highlighting the need for improved diagnosis and prevention strategies. While the etiology of RA remains complex and less well-defined, studies have suggested that dietary factors may potentially contribute to RA development.

Reports suggest that dietary fiber may have therapeutic effects against inflammatory disorders. Various benefits of higher fiber consumption have been reported, including reduced systemic inflammation in RA subjects. Inflammation is a crucial factor in RA development, and the dietary inflammatory index (DII) is a pivotal tool to assess a diet’s overall inflammatory potential.

About the study

The present study investigated the associations of dietary fiber consumption with RA risk. The team used data from the National Health and Nutrition Examination Survey (NHANES) conducted in the United States (US) between 2011 and 2020. The survey, representative of the non-institutionalized US population, was conducted by the National Center for Health Statistics.

Participants with extreme energy intake, missing (covariate and dietary intake) data, and those without RA data were excluded. A nutritionist conducted two 24-hour dietary recall sessions: an in-person session and a telephone session within 3–10 days. The mean fiber intake was estimated, and sources of dietary fiber included fruits, vegetables, and grains.

A questionnaire was administered to investigate participants’ arthritis or RA status. Further, the team estimated the DII score by assessing dietary markers. Covariates were age, sex, body mass index (BMI), race, menopause status, energy intake, alcohol status, smoking status, education, waist circumference, family income-to-poverty ratio, and physical activity.

Demographic data were stratified by RA status and evaluated using t- and chi-squared tests. Logistic regression methods were applied to explore the association between fiber intake, inflammatory markers, and RA prevalence. The intermediary role of DII in the relationship between RA onset and fiber intake was examined.

Findings

Of the 32,451 NHANES respondents during 2011-20, 15,114 subjects were retained for analysis, following exclusion criteria. Participants’ average age at the time of evaluation was 46.37, and around 7% had RA. The mean total fiber intake was 15.37 g/day among RA subjects and 17.12 g/day among those without RA. Individuals with RA were predominantly female, older, and had higher BMI and lower education and income compared to non-RA subjects.

Participants with RA were also more likely to smoke, consume alcohol, and less likely to engage in physical activity. The team observed an inverse association between total fiber intake and RA emergence. Additionally, fiber intake was stratified into tertiles in a sensitivity analysis. This revealed that individuals in the top-most tertile (of fiber intake) had a one-fourth decrease in RA prevalence relative to those in the lowest tertile.

Furthermore, among dietary fiber sources, cereal fiber intake had a significant inverse correlation with RA, which was more pronounced in a sensitivity analysis. By contrast, the association of fruit and vegetable fiber with RA was inconclusive. The researchers noted that the total fiber intake was significantly inversely related to DII and high-sensitivity C-reactive protein.

There was a similar trend for vegetable or cereal fiber intake. A positive correlation was observed between DII and RA prevalence, indicating a 26% increase in RA prevalence with one-unit increments in DII. Data suggested a mediating role of DII in the association between fiber intake (36.12% for total fiber intake and 40.35% for cereal fiber intake) and RA incidence.

Conclusions

The findings revealed a correlation between sub-optimal fiber intake and higher RA prevalence. DII was identified as a critical intermediary in this association. Although DII provides a comprehensive assessment of a diet’s inflammatory potential, it is noteworthy that several dietary components may impact the DII. Moreover, the dietary recall approach has limitations, such as poor accuracy and over- or under-reporting.