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J Ren Nutr. 2001 Jan;11(1):32-6.

Clay pica has no hematologic or metabolic correlate in chronic hemodialysis patients.

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Department of Medicine, Morehouse School of Medicine, Atlanta, GA 30310, USA.



Clay pica is a form of compulsive ingestion of non-nutritive substances frequently practiced by dialysis patients. Its consequences are unknown. In this study, we evaluated the effect of regular consumption of clay on hematologic and metabolic profiles in hemodialysis patients.


A prospective, case-control study with use of structured questionnaire.


Free-standing hemodialysis units.


One hundred thirty-eight patients on hemodialysis for at least 12 months were interviewed. Thirteen of 138 (9.4%) confessed to clay pica. Ten randomly selected patients with no history of pica served as control.


Average of all laboratory profiles and interdialytic weight gain (IDWG) over a 3-month period were recorded. Assay of the aluminum (Al), silica (Si), and iron (Fe) content of commercially purchased clay was performed.


Comparison of laboratory profiles and IDWG between cases and control. Estimation of the daily consumption of Al, Fe, and Si from clay and their relationship to the laboratory profiles.


There was no statistically significant difference in the levels of Al, albumin, calcium, ferritin, hematocrit, iron saturation, phosphorus, and IDWG between pica cases and control. Iron was significantly higher in pica patients (13.0 +/- 7.9 micromol/L v 7.5 +/- 2.5 micromol/L, P =.04), but potassium was higher among control than pica cases (4.9 +/- 0.7 mmol/L v 4.4 +/- 0.6 mmol/L, P =.07). Estimated metal exposure from daily clay consumption per patient were: Al (1-2 mg), Fe (11-23.5 mg), and Si (2-4.5 g). Multivariate logistic regression analysis failed to show any association between clay consumption and nutrition, anemia, or mineral metabolism (R(2) = 0.0, P =.79).


Clay pica does not appear to be detrimental to the hematologic and metabolic milieu of hemodialysis patients. The practice should, however, be discouraged, because of potential for ingestion of unknown substances, and reported potential for gastrointestinal complications.

[Indexed for MEDLINE]

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