Association between caffeine intake and constipation in a U.S. population aged 20 to 65 years - Results from NHANES 2007 to 2010

Q: How was constipation defined in the NHANES-based analysis?

Constipation was defined using stool form, bowel movement frequency, and self-reported symptoms.

Q: Did the association show a nonlinear or threshold pattern?

Yes. Restricted cubic spline analyses supported a nonlinear relationship, with the curve crossing the null at approximately 580 mg/day and no further benefit at higher intakes.

Sep 30, 2026

Uploaded by Ben

Caffeine’s relationship with constipation remains unclear, with studies suggesting both potential promotion of bowel movement and worsening symptoms when intake is excessive. This cross-sectional study assessed the association between caffeine intake and constipation among U.S. adults aged 20–65 using NHANES 2007–2010 data. Caffeine intake was grouped into quartiles, while constipation was defined by stool form, bowel movement frequency, and self-reported symptoms. Weighted multivariable logistic regression and restricted cubic splines showed lower constipation odds at moderate intake with evidence of a nonlinear threshold effect.

LanguageEnglish

CategoryHealthcare

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® Observational Study Association between caffeine intake and constipation in a U.S. population aged 20 to 65 years Results from NHANES 2007 to 2010 Haokang Li, MMeda , Huanhuan Wang, MDb ,* | Abstract
Caffeine’s relationship with constipation is unclear. Some studies suggest caffeine may promote bowel movement, while excessive intake could worsen symptoms. This cross-sectional study aimed to evaluate the association between caffeine intake and constipation among U.S. adults aged 20 to 65 years using data from the 2007 to 2010 National Health and Nutrition Examination Survey. Caffeine intake was categorized into quartiles based on 24-hour dietary recall data, and constipation was defined using stool form, bowel movement frequency, and self-reported symptoms. Weighted multivariable logistic regression, restricted cubic spline modeling, and subgroup and interaction analyses were conducted to assess associations and test the robustness of results. Compared with participants in the lowest quartile of caffeine intake (≤35 .5 mg/d), those in the third quartile (109 .1– 228.5 mg/d) had the lowest odds of constipation (odds ratio [OR]: 0.60; 95% confidence interval: 0.44–0.82; P = .004) . When modeled on a log2 scale, each doubling of caffeine intake was associated with a modest reduction in the odds of constipation (OR: 0 .95, 95% confidence interval: 0 .91–0.99; P = .019) . Restricted cubic spline analyses supported a nonlinear association (P for nonlinear < .01); the curve crossed the null (OR = 1) at approximately 580 mg/d, with no further benefit observed at higher intakes. No significant effect modification was detected across prespecified subgroups. Moderate caffeine consumption was associated with a lower likelihood of constipation, whereas higher caffeine intake did not confer additional benefits. These findings suggest a potential threshold effect of caffeine on bowel function, beyond which further intake may not provide added advantage. Further longitudinal and mechanistic studies are warranted to confirm these associations and clarify the biological pathways linking caffeine consumption to bowel motility. | | --- | | Abbreviations: BMI = body mass index, CI = confidence interval , OR = odds ratio, PIR = poverty income ratio, RCS = restricted cubic spline. | | Keywords: caffeine, constipation, cross-sectional study, NHANES | 1. Introduction Chronic constipation, one of the most common functional bowel disorders, affects approximately 8% of adults in the United States according to Rome IV criteria, with significantly higher prevalence among women, and is associated with marked reductions in quality of life and increased gastrointestinal healthcare utilization. [1] The etiology of constipation is multifactorial, with contributions from dietary habits, lifestyle choices, psychological health, and socioeconomic determinants. [2] Consequently, modifications to diet and lifestyle are considered foundational strategies for its prevention and management. [3] Caffeine, a methylxanthine alkaloid and the most widely consumed psychoactive substance globally, is known to exert various physiological effects, including on the gastrointestinal system. [4] However, the association between caffeine intake and constipation remains equivocal, with extant literature presenting conflicting findings. Some evidence suggests a protective association, potentially mediated by caffeine’s prokinetic effects on colonic motor activity and its capacity to favorably modulate the gut microbiota. [5] Conversely, other studies indicate that excessive caffeine consumption could potentially exacerbate constipation or contribute to symptoms of irritable bowel syndrome, possibly by inhibiting intestinal motility in certain contexts.[6]The divergent findings in the literature suggest the possibility of a nonlinear, dose-dependent relationship between caffeine intake and the odds of constipation.[7] Therefore, this study aims to investigate the

FAQs

How was constipation defined in the NHANES-based analysis?

Constipation was defined using stool form, bowel movement frequency, and self-reported symptoms.

What statistical methods were used to evaluate the caffeine–constipation association?

Weighted multivariable logistic regression, restricted cubic spline modeling, and subgroup and interaction analyses were applied to assess associations and robustness.

Did the association show a nonlinear or threshold pattern?

Yes. Restricted cubic spline analyses supported a nonlinear relationship, with the curve crossing the null at approximately 580 mg/day and no further benefit at higher intakes.

Sep 30, 2026

Uploaded by Ben