Harvard Medical School Division of Nutrition

Nancy Krebs, M.D.
Professor of Pediatrics
Head, Section of Nutrition
Department of Pediatrics
University of Colorado Health Sciences Center

Zinc: Is It a Protective Nutrient?

Zinc is an essential nutrient and has physiologic functions that are directly related to normal functioning of the gastrointestinal tract and immune system. Because of its efficacy in the prevention and treatment of acute and persistent diarrhea, zinc has been proposed as a protective nutrient, which implies that there are beneficial functions “separate and distinct from its role as a nutrient.√ì The evidence for this will be reviewed in relation to normal zinc homeostasis and the effects of diarrhea on homeostasis. The results of large RCT examining zinc as a preventive and therapeutic agent for diarrhea will be reviewed. A recent meta-analysis concluded that, in areas where diarrhea is a prominent cause of child morbidity and mortality, [supplemental] zinc is clearly of benefit for young children over 6 months of age. Results of recent negative trials will also be discussed. Although doses of zinc used in supplementation trials have generally been well above dietary zinc requirements, underlying mechanisms for potential pharmacologic effects in the gastrointestinal tract and immune function are less well developed. It is concluded that the weight of available evidence suggests that the effect of Zn supplementation on diarrhea is correction of Zn deficiency, and thus not necessarily distinct from its role as a nutrient. Whether zinc is a “protective nutrient√ì is less clear. A compelling need exists for interdisciplinary research on mechanisms and interactions between host, diet, and environment to develop sound approaches to improve public health.