A meta-analysis of pica and micronutrient status

Abstract

Objectives: Pica is the craving for and consumption of nonfood items, including the ingestion of earth (geophagy), raw starch (amylophagy), and ice (pagophagy). Pica has long been associated with micronutrient deficiencies, but the strength of this relationship is unclear. We aimed to evaluate the association between pica behavior and the risk of being anemic or having low hemoglobin (Hb), hematocrit (Hct), or plasma zinc (Zn) concentrations.

Methods: We systematically reviewed studies in which micronutrient levels were reported by pica status. We calculated the pooled odds ratio for anemia or weighted mean difference in Hb, Hct, or Zn concentrations between groups practicing or not practicing pica behaviors.

Results: Forty-three studies including 6,407 individuals with pica behaviors and 10,277 controls were identified. Pica was associated with 2.35 times greater odds of anemia (95% CI: 1.94-2.85, P < 0.001), lower Hb concentration (-0.65 g/dl, 95% CI: -0.83 to -0.48 g/dl, P < 0.001), lower Hct concentration (-1.15%, 95% CI: -1.61 to -0.70%, P < 0.001), and lower Zn concentration (-34.3 μg/dl, 95% CI: -59.58 to -9.02 μg/dl, P = 0.008). Statistical significance persisted after excluding outliers and in subgroup analyses by pica type and life stage.

Conclusion: Pica is significantly associated with increased risk for anemia and low Hb, Hct, and plasma Zn. Although the direction of the causal relationship between pica and micronutrient deficiency is unknown, the magnitude of these relationships is comparable to other well-recognized causes of micronutrient deficiencies. Pica warrants greater public health attention; specifically the potential physiological mechanisms underpinning the relationship between pica and micronutrient deficiencies merit further study.

Fig. 1. Flowchart of study selection process

* Several articles measured more than one biomarker, so the number of studies used in each analysis do not sum to 43.

Fig. 2. Forest plots of effect of pica on anemia

Horizontal displacement of squares represents odds ratio (OR) with square size proportional to study weight in the meta-analysis. Horizontal lines represent 95% CI. Studies are organized by increasing weight. The hollow diamond indicates the pooled OR and 95% CI. (A) Pooled estimate of OR of pica behavior associated with anemia is shown for n=32 studies. (B) Pooled estimate of OR of geophagy behavior associated with anemia (n=12). (C) Pooled estimate of OR of pagophagy behavior associated with anemia (n=6) (D) Pooled estimate of OR of amylophagy behavior associated with anemia (n=4) (E) Pooled estimate of OR of pica behavior associated with anemia in children (n=5). (F) Pooled estimate of OR of pica behavior associated with anemia in pregnant women (n=23). ¹Data for amylophagy only. ²Data for geophagy only.

Fig. 3. Forest plots of effect of pica on hemoglobin

Horizontal displacement of squares represents weighted mean difference (WMD), with square size proportional to study weight in the meta-analysis. Horizontal lines represent 95% CI. Studies are organized by increasing weight. The hollow diamond indicates the pooled OR and 95% CI. (A) Pooled estimate of WMD of pica behavior associated with hemoglobin (Hb) concentration (g/dL) for n=23 studies (B) Pooled estimate of WMD of geophagy behavior associated with Hb concentration (n=11). (C) Pooled estimate of WMD of pica behavior associated with Hb concentration in children (n=10). (D) Pooled estimate of WMD of pica behavior associated with Hb concentration in pregnant women (n=9). ¹Children aged 6 months to 3 years with clay pica. ²Children aged 4 to 15 years with dirt and plaster pica. ³Children aged 6 months to 3 years with dirt and plaster pica. ⁴Children aged 4 to 15 years with clay pica. ⁵Males only. ⁶Females only.

Fig. 4. Forest plots of effect of pica on hematocrit

Horizontal displacement of squares represents weighted mean difference (WMD), with square size proportional to study weight in the meta-analysis. Horizontal lines represent 95% CI. Studies are organized by increasing weight. The hollow diamond indicates the pooled OR and 95% CI. (A) Pooled estimate of WMD of pica behavior associated with hematocrit (Hct) (%) for n=9 studies. (B) Pooled estimate of WMD of pica behavior associated with Hct (%) in pregnant women (n=6). ¹Males only. ²Females only.

Fig. 5. Forest plots of effect of pica on plasma zinc

Horizontal displacement of squares represents weighted mean difference (WMD), with square size proportional to study weight in the meta-analysis. Horizontal lines represent 95% CI. Studies are organized by increasing weight. The hollow diamond indicates the pooled OR and 95% CI. Pooled estimate of WMD of pica behavior associated with plasma zinc (Zn) (ug/dL) for n=5 studies.