Pagophagia (compulsive ice chewing) has long been associated with iron deficiency anemia, but prior attempts to account for this craving have been unsatisfactory. We hypothesize that chewing ice triggers vascular changes that lead to preferential or increased perfusion of the brain. This would result in increased alertness and processing speed in anemic patients, but not in healthy controls who are already at ceiling, and would explain why anemic individuals crave ice. Preliminary support for this hypothesis was found in two studies. In Study 1, non-anemic subjects reported very low rates of pagophagia (only 4%) while anemic subjects reported significantly higher rates (56%). In Study 2, chewing ice dramatically improved response time on a neuropsychological test, but only for anemic individuals. In a small randomized controlled trial, iron deficient anemic subjects and healthy controls were assigned to chew ice or drink tepid water and then took a continuous performance test that measures response time, response time variability, errors of impulsivity and errors of inattention. In the water condition, anemic subjects performed significantly worse than healthy controls. Chewing ice had no effect on the performance of healthy controls, but significantly improved the performance of anemic patients. Potential explanations include activation of the dive reflex, which would lead to peripheral vasoconstriction and preferential perfusion of the brain or, alternatively, sympathetic nervous system activation, which would also increase blood-flow to the brain.
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