Roy et al (J. Health, Population and Nutrition 24:1, 2006) recently found reduced intestinal absorption of electrolytes and an enhanced secretory response to cholera toxin in young rats deprived of dietary zinc. These interesting findings warrant further study but they also emphasize some of the difficulties in interpreting nutrititional studies.

Two questions that arise from this paper are:

1. Were the study rats truly zinc deficient?

Apparently their zinc status was not measured. Judging from body weight data which leveled off in the Zn-deprived group, these rats had global deficiencies of most macro- and micro nutrients. Dietary intake data are not provided. In general, rats are not good models for studying human nutritional problems for various reasons including their dependence on coprophagy and because their food intake is very difficult to measure reliably.

2. Were the abnormalities observed in transport a response to zinc deficiency, to protein-calorie malnutrition, to folic acid depletion, etc. or all of the above?

Exploration of the relationships between enteric infections and nutritional deficiencies continues to be an important research priority. The complexities of these relationships have many possible pitfalls which means that study designs and data interpretation must be rigorous.

Do you have comments on the study cited above or on the nutritional research issues it raises?