Background: We studied the association of zinc deficiency and childhood-onset anorexia nervosa because the relationship is controversial.
Method: Anorexia nervosa was diagnosed on the basis of determined food avoidance, weight loss, preoccupation with body weight and energy intake, distorted body image, fear of fatness, self-induced vomiting, excessive exercising, and laxative abuse. Twenty-six such children, admitted to a specialized eating disorders program within a children's hospital, formed the basis of the study. Zinc status was determined by measuring fasting plasma zinc levels and 24-hour urinary zinc excretion using atomic absorption spectrophotometry. Nutritional status was determined by using weight-for-height ratios. A trial of zinc supplementation was attempted using a 12-week double-blind crossover design, with 6 weeks of placebo and 6 weeks of treatment with 50 mg daily of oral zinc sulphate.
Results: Zinc deficiency was found to be common, with a significant correlation between fasting plasma zinc levels and malnutrition (Pearson r = .586, p = .004). Introduction of a normal diet rapidly returned zinc levels and weight-for-height ratios to the normal range. Children entering the study with relatively normal zinc levels gained weight no faster than those with low plasma zinc levels. Of seven trials of zinc supplementation, only three were completed, as inadequate oral intake threatened the health of the remaining four.
Conclusion: Low zinc levels are common in childhood-onset anorexia nervosa, appear to be secondary to self-starvation, and are rapidly reversible without zinc supplementation.