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Background <p>The relationship between overall dietary antioxidant potential and risk of irritable bowel syndrome (IBS) is unclear and needs further epidemiologic evidence.</p> Methods <p>In this study, we included a total of 157,900 participants from the UK Biobank without irritable bowel syndrome at baseline between 2006 and 2010. Dietary intake was assessed using the online 24-hour dietary recall questionnaire, Oxford WebQ. IBS was identified using the ICD-10 code (K58). The composite dietary antioxidant index (CDAI) was the sum of Z scores for mean intake of individual vitamins A, C, E, manganese, selenium, and zinc from five 24-hour dietary recalls.</p> Results <p>During a mean follow-up time of 13.41 years, 2,007 incident cases of IBS were identified among the 157,900 participants. Restricted cubic spline (RCS) showed a nonlinear association (<i>p</i> for nonlinear &lt; 0.001) between CDAI and the risk of IBS, and two-piecewise linear regression identified an inflection point at -0.9. Segmented Cox regression demonstrated that increasing CDAI significantly reduced the risk of IBS when CDAI &lt; -0.9 (HR: 0.900, 95% CI: 0.820–0.988, <i>P</i> = 0.027); however, when CDAI ≥ -0.9, there was a 3% increased risk of IBS (HR: 1.030, 95% CI: 1.001–1.060, <i>P</i> = 0.046). Furthermore, compared to participants in Quintile 2 of CDAI, individuals in Quintile 1 had a 23% increased risk of IBS (HR: 1.228, 95% CI: 1.071–1.408, <i>P</i> = 0.003), while no significant differences were observed for participants in the other quintiles. Nonlinear analysis of independent dietary nutrients suggested a significant U-shaped association only between vitamin C and the risk of IBS, with an inflection point at Z score = -0.1. Sensitivity analyses with multiple imputation for missing covariates supported a negative association between antioxidant intake and IBS risk before the inflection point of CDAI. In contrast, after the inflection point, CDAI seemed to be unrelated to IBS risk.</p> Conclusion <p>Moderate supplementation of antioxidants, particularly vitamin C, is beneficial in reducing the risk of IBS. However, excessive intake of dietary antioxidants tends to have no protective effect on IBS risk.</p>

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Nonlinear association between composite dietary antioxidant index and irritable bowel syndrome: insights from UK Biobank

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月1日

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  • Laifu Li,
  • Yan Zhuang,
  • Yan Ran,
  • Lianli Wang,
  • Jiamiao Chen,
  • Lin Mei,
  • Fangchen Ye,
  • Yating Sun,
  • Zhuoya Sun,
  • Shiwei Lu,
  • Yu Ning,
  • Fei Dai

摘要

Background

The relationship between overall dietary antioxidant potential and risk of irritable bowel syndrome (IBS) is unclear and needs further epidemiologic evidence.

Methods

In this study, we included a total of 157,900 participants from the UK Biobank without irritable bowel syndrome at baseline between 2006 and 2010. Dietary intake was assessed using the online 24-hour dietary recall questionnaire, Oxford WebQ. IBS was identified using the ICD-10 code (K58). The composite dietary antioxidant index (CDAI) was the sum of Z scores for mean intake of individual vitamins A, C, E, manganese, selenium, and zinc from five 24-hour dietary recalls.

Results

During a mean follow-up time of 13.41 years, 2,007 incident cases of IBS were identified among the 157,900 participants. Restricted cubic spline (RCS) showed a nonlinear association (p for nonlinear < 0.001) between CDAI and the risk of IBS, and two-piecewise linear regression identified an inflection point at -0.9. Segmented Cox regression demonstrated that increasing CDAI significantly reduced the risk of IBS when CDAI < -0.9 (HR: 0.900, 95% CI: 0.820–0.988, P = 0.027); however, when CDAI ≥ -0.9, there was a 3% increased risk of IBS (HR: 1.030, 95% CI: 1.001–1.060, P = 0.046). Furthermore, compared to participants in Quintile 2 of CDAI, individuals in Quintile 1 had a 23% increased risk of IBS (HR: 1.228, 95% CI: 1.071–1.408, P = 0.003), while no significant differences were observed for participants in the other quintiles. Nonlinear analysis of independent dietary nutrients suggested a significant U-shaped association only between vitamin C and the risk of IBS, with an inflection point at Z score = -0.1. Sensitivity analyses with multiple imputation for missing covariates supported a negative association between antioxidant intake and IBS risk before the inflection point of CDAI. In contrast, after the inflection point, CDAI seemed to be unrelated to IBS risk.

Conclusion

Moderate supplementation of antioxidants, particularly vitamin C, is beneficial in reducing the risk of IBS. However, excessive intake of dietary antioxidants tends to have no protective effect on IBS risk.