Original Contribution

Functional GI Disorders

Characterizing Normal Bowel Frequency and Consistency in a Representative Sample of Adults in the United States (NHANES)

  • The American Journal of Gastroenterology volume 113, pages 115123 (2018)
  • doi:10.1038/ajg.2017.213
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Our current understanding of normal bowel patterns in the United States (US) is limited. Available studies have included individuals with both normal and abnormal bowel patterns, making it difficult to characterize normal bowel patterns in the US. The current study aims to (1) examine frequency and consistency in individuals with self-reported normal bowel habits and (2) determine demographic factors associated with self-reported normalcy.


This study used data from adult participants who completed bowel health questions as part of the National Health and Nutrition Examination Survey (NHANES) in 2009–2010 and who reported normal bowel patterns (N=4,775). Data regarding self-perceived bowel health; stool frequency; stool consistency (using the Bristol Stool Form Scale (BSFS)); and demographic factors were analyzed.


95.9% of the sample reported between 3 and 21 BMs per week. Among men, 90% reported a BSFS between 3 and 5, while for women it was 2–6. After controlling for age, the following demographic variables were associated with normalcy: male sex, higher education, higher income, <2 daily medications, and high daily fiber intake. Hispanic ethnicity was significantly associated with abnormal self-reported bowel habits.


This is the first study to evaluate normal bowel frequency and consistency in a representative sample of adults in the US. The current findings bolster the common “3 and 3” metric of normal frequency (3 BMs/day to 3 BMs/week) while also suggesting different criteria for normal consistency for men and women. Finally, this study provides novel information about demographic factors associated with normal frequency and consistency.

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Author information


  1. Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA

    • Shuji Mitsuhashi
    • , Sarah Ballou
    • , Zhenghui G Jiang
    • , William Hirsch
    • , Judy Nee
    • , Johanna Iturrino
    • , Vivian Cheng
    •  & Anthony Lembo


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Competing interests

Guarantor of the article: Anthony Lembo, MD.

Specific author contributions: The idea for the article was conceived by A.L and Z.G.J. The manuscript was drafted by S.B. and S.M. Statistical analysis was performed by S.M. and Z.G.J. The draft manuscript was critically reviewed by W.H., J.N., J.I, and V.C. All authors reviewed and approved the final version of the manuscript.

Financial support: This project was funded in part by T32DK007760.

Potential competing interests: None.

Corresponding author

Correspondence to Anthony Lembo.