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Original research
Relationship between dietary magnesium intake and rheumatoid arthritis in US women: a cross-sectional study
  1. Congqi Hu1,
  2. Fangfang Zhu1,
  3. Lijuan Liu2,
  4. Mingying Zhang2,
  5. Guangxing Chen2
  1. 1First Clinical Medical College, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, China
  2. 2Department of Rheumatology, the First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, China
  1. Correspondence to Dr Guangxing Chen; cgx02{at}


Objectives Diet has been shown to be associated with rheumatoid arthritis (RA), and magnesium has been shown to inhibit inflammatory responses, but research on the relationship between dietary magnesium and RA is limited and controversial. In this study, we aimed to explore the non-linear relationship between dietary magnesium intake and RA in US women.

Design Cross-sectional survey.

Setting National Health and Nutrition Examination Survey (NHANES).

Primary and secondary outcome measures Non-linear relationship between dietary magnesium intake and prevalence of RA.

Participants A total of 13 324 women aged 18–80 years (RA n=12 306, non-RA n=1018) were included in this study.

Results Overall, the absolute risk (AR) of RA was 7.24% in all participants. In the multivariable logistic regression analysis, we found a negative correlation between dietary magnesium intake and RA (OR=0.84, 95% CI 0.75 to 0.95, p=0.006). When we converted dietary magnesium intake into a categorical variable (tertiles), the ARs of the low group, the middle group and the high group were 9%, 7.1% and 4.9%, respectively. We noticed that the ORs between the three groups were not equidistant; then, we detected a U-shaped linking by smooth curve fitting and obtained inflection points at 181 and 446 mg/day. The prevalence of RA decreased when dietary magnesium intake was <181 mg/day (OR=0.7, 95% CI 0.5 to 0.8, p<0.001) and increased when it was >446 mg/day (OR=2.8, 95% CI 1.2 to 6.6, p=0.020), remaining at a minimum when it was between 181 and 446 mg/day (OR=1.0, 95% CI 0.7 to 1.2, p=0.700).

Conclusion There was a U-shaped relationship between dietary magnesium and RA in women, and our study highlights the importance of moderate dietary magnesium intake in possibly exerting a protective role in women with RA.

  • nutrition & dietetics
  • rheumatology
  • public health
  • rheumatology

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  • Contributors GC was responsible for designing the study, guiding the manuscript development and substantially revising the paper. CH and FZ were responsible for conducting the statistical analyses, writing the first version of the manuscript and interpreting results. LL was responsible for involving in data processing and editing the manuscript. MZ contributed to data extraction and provided feedback on the study.

  • Funding This work was supported by the Chinese National Natural Science Foundation Project (grant number 81573850); the Science and Technology Program of Guangzhou (grant number 201904010336); the Innovative and Strong Hospital Phase II Project of the First Affiliated Hospital of Guangzhou University of Chinese Medicine, which is a part of High-level Hospital Construction Project of Guangdong Provincial Government (grant number 211010010705). These funders had no role in the design, analysis or writing of this article.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting or dissemination plans of this research.

  • Patient consent for publication Obtained.

  • Ethics approval NHANES approved by the National Center for Health Statistics Research Ethics Review Board under Continuation of Protocol.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available in a public, open access repository. Open access data are available on the NHANES website.