Calcium Supplementation Does Not Contribute to Constipation in Healthy Women

Can J Diet Pract Res. 2016 Jun;77(2):103-5. doi: 10.3148/cjdpr-2015-043. Epub 2016 Jan 15.


Purpose: It is commonly suggested that calcium supplementation contributes to constipation; however, little research has explored the effects of calcium supplementation on gut motility.

Methods: In an 8-week, randomized, double-blind, crossover pilot study, healthy females (n = 27, aged 43.0 ± 10.6 years) received a split dose of 500 mg/d of elemental calcium from calcium carbonate or calcium phosphate each for 2 weeks, after a 2-week baseline and separated by a 2-week washout. Participants completed daily questionnaires of stool frequency, Bristol Stool Form Scale (BSFS), and supplement intake compliance.

Results: There were no differences among periods. Mean ± SE stool frequency averaged 1.3 ± 0.1 stools/d in each period. Participants reported 34%, 34%, 37%, and 29% of stools were indicative of slow transit or constipation (BSFS of 1 or 2) during baseline, calcium carbonate, calcium phosphate, and washout periods, respectively. Participants also reported from 6% to 10% of stools as fast transit or diarrhea (BSFS of 6 or 7) during the periods.

Conclusion: This study suggests that neither calcium carbonate nor calcium phosphate, providing 500 mg/d of calcium, affects stool frequency or form. Although stool frequency was normal, the healthy females participating in the study experienced stools indicating slow (constipation) and fast (diarrhea) transit.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Body Mass Index
  • Calcium Carbonate / administration & dosage
  • Calcium Carbonate / adverse effects
  • Calcium Phosphates / administration & dosage
  • Calcium Phosphates / adverse effects
  • Calcium, Dietary / administration & dosage*
  • Calcium, Dietary / adverse effects*
  • Constipation / diagnosis*
  • Constipation / etiology
  • Cross-Over Studies
  • Dietary Supplements*
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Feces / chemistry
  • Female
  • Healthy Volunteers
  • Humans
  • Middle Aged
  • Pilot Projects
  • Surveys and Questionnaires


  • Calcium Phosphates
  • Calcium, Dietary
  • calcium phosphate
  • Calcium Carbonate