Physiology & Bel~avior, Vol. 18, pp. 885-893. Pergamon Press and Brain Research Publ., 1977. Printed in the U.S.A. A Nutritional Basis for Lead Pica' CHARLES T. SNOWDON 2 University of Wisconsin, Madison, WI 53706 (Received 29 May 1976) SNOWDON, C. T. A nutritional basis for lead pica. PHYSIOL. BEHAV. 18(5) 885-893, 1977. Lead pica is a puzzling behavioral phenomenon involving the continued voluntary ingestion of a toxic substance. Calcium deficiency produced an elevated proportion of lead ingestion while magnesium and zinc deficiency produced proportional levels of lead ingestion intermediate to control and calcium deficient rats. Partrial restoration of calcium did not eliminate the increased proportion of lead ingestion while full calcium restoration did. Calcium deficient rats offered lead to drink gained more weight than deficient rats not offered lead. Control animals showed a reduction in their intake of novel solutions ingested ft~llowing intubation of lead acetate while calcium deficient animals did not. Rats deficient in calcium, iron and zinc also showed elevated proportional levels of quinine sulfate ingestion compared to controls suggesting that a pica may be a general response to nutritional deficiency. The increased proportion of lead ingestion by calcium, zinc and magnesium deficient rats and the failure of calcium deficient rats to form a learned aversion to lead acetate, suggests thal mineral deficiency may be a major factor in producing lead pica. Lead pica Calcium deficiency Iron deficiency Zinc deficiency Magnesium deficiency Taste aversion VOLUNFARY lead ingestion (lead pica [from the ingestive behavior of the magpie, Pica pica pica] ) has been estimated to occur in as many as 225,000 U.S. children each year [21]. The prolonged ingestion of lead leads to severe gastrointestinal distress, ataxia, brain damage and mental retardation [5, 6, 23, 26]. A variety of suggestions for why lead pica should occur have been proposed: Disrupted oral needs due lo lack of care by mother; excessive oral gratification resulting from an overly attentive mother; symbolic aggression directed toward the mother; and brain damage [ 141. None of these explanations are biologically satisfying, and none are sufficient to account for all aspects of lead pica behavior. It is commonly reported that children generally engage in mouthing of objects at the age when lead pica appears (15 30 months) [4,181, and it has been proposed that ingestion of lead may occur through chance encounters that the child has with objects containing lead. However, several investigators have noted that there is a strong persistence in lead ingestion even after the development of the painful, debilitating symptoms resulting from lead poisoning. Seven of 20 case studies presented by Byers and Lord [61 continued lead pica after treatment for lead poisoning. Smith, Baehner, Carney and Jacobs [27] reported that 19% of their lead intoxicated patients returned to lead pica. Woods and Waiters [35] report a single case history where the child continued to ingest lead. Lourie etal. [14] state that many of their patients continued lead pica, while Mellins and Jenkins [17] actually attempted to substitute nontoxic objects for lead containing objects with no success. This persistence of lead pica as a specific hunger that continues past the development of toxic symptoms raises a variety of interesting questions. One of the most common findings with other picas is that the seemingly abnormal ingestive behaviors often have a direct relationship to a nutritional deficiency. Thus, picas are often adaptive ingestive behaviors. For example, South African cattle which were ingesting bones were eventually shown to have a phosphorous deficiency [9]. Peruvian Indians of the Altiplano use powdered limestone to season their food which is otherwise deficient in calcium [3,12]. Since lead posioned children often suffer an iron deficiency anemia [32], it has been proposed that iron deficiency might be the motivating force behind lead ingestion. However, evaluation of the diets of children with lead pica, and attempts to eliminate lead pica by the injection of large amounts of iron have provided no support for the notion that iron deficiency produces lead pica [ 10, 11, 191. A nutritional agent which might be related to lead ingestion is calcium. Calcium is one of the nutrients most likely to be deficient in the diets of low income children- the population with the highest incidence of lead ingestion. In a Texas survey [30] it was found that low income white children ingested only 73~? of the recom- mended daily calcium levels, and low income blacks ingested only 47% of recommended levels. A survey of children in Mississippi [22] found a direct relationship between income and amount of calcium in the diet. Several physiological studies suggest a relationship between calcium and lead. There is an increased absorption 'Supported by U.S.P.H.S. C-ranl AM 17,171. 1 am grateful to Paula Machtinger Yvonne Pola, James Sanders and JeanSmithana for their assistance with these experiments. 2 Address reprint requests to: Charles T. Snowdon, Department of Psychology, Charter at Johnson Street, University of Wisconsin, Madison, Wl 53706. 885