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Reply to RJ Walden

Instituto de Investigacion Nutricional
Av. La Universidad 685 –La Molina
Apartado 18-0191
Lima 12
Peru
E-mail: mpenny{at}iin.sld.pe
Department of International Health
Johns Hopkins Bloomberg School of Public Health
Baltimore, MD
Program in International Nutrition and Department of Nutrition
University of California, Davis
Davis, CA
Department of Nutrition
University of California, Davis
Davis, CA

Dear Sir:

We thank Dr Walden for his interest in our study (1).

We administered zinc along with the other minerals to children in one group in our study to facilitate distribution of the supplements and adherence to the treatment regimen. We found lower concentrations of plasma zinc in the group receiving zinc plus minerals than in the groups receiving placebo or zinc only; our suggestion that the most likely explanation was an interaction between zinc and iron, which also has been described in other studies (2), is in keeping with Walden's expectation. Nevertheless, the reduction in plasma zinc was relative, and the mean concentration in the group receiving zinc plus micronutrients remained significantly higher than that in the control group, so the multiple micronutrients given with the zinc has a positive effect on this indicator of zinc status. There is a tradeoff between the lower absorption that is due to mineral interactions and a simplified dosing regimen with the probable result of higher compliance. We agree that further work is needed to explore the best way of delivering multinutrients in practical ways that diminish the interaction between nutrients while facilitating compliance.

Walden comments that we did not include calcium, chromium, manganese, and iodine. Calcium was not included because of the technical problems caused by its bulk. Iodine was not included because, in Lima, all salt is fortified with iodine. Chromium is an essential mineral that is important in glucose tolerance. Although one study found improved growth when severely malnourished children were supplemented with chromium (3), we are not aware of any positive effect of chromium on the growth on children who are not severely malnourished. There are no studies of dietary intakes of chromium in Lima children, and such studies would have to take into account the possible contribution of chromium from canned foods and from river water that is contaminated by industrial waste. Although it is possible that there is dietary deficiency, none of the 3 groups of children received supplements of chromium, so that mineral cannot explain the differences between the groups; however, we cannot exclude the possibility that chromium deficiency masked an effect on growth. Although manganese is considered an essential trace element for animals, there is little information on a clinically important deficiency in humans and, as far as we know, there are no studies that show an effect of manganese supplementation on growth or morbidity. All plant-based foods as well as milk are good sources of manganese, and it is highly probable that the children received adequate quantities from their diet. We think it unlikely that the absence of manganese affected the outcome of our study.

The amounts of vitamin B-12 and folate included were determined by the content of the multivitamin-mineral mix that we were able to obtain from a commercial company for this study. Although the amounts were higher than the current dietary recommended intakes for these water-soluble vitamins, we know of no adverse effects attributed to these doses. Tartrazine was added locally to mask the yellow color due to retinal palmitate in the zinc plus micronutrients supplements and to ensure that the supplements were indistinguishable. It was the only generally accepted as safe yellow food coloring available in Lima.

REFERENCES

1. Penny ME, Marin RM, Duran A, et al. Randomized controlled trial of the effect of daily supplementation with zinc or multiple micronutrients on the morbidity, growth, and micronutrient status of young Peruvian children. Am J Clin Nutr 2004;79:457–65.[Abstract/Free Full Text]
2. Lind T, Lönnerdal B, Stenlund H, et al. A community-based randomized controlled trial of iron and zinc supplementation in Indonesian infants: interactions between iron and zinc. Am J Clin Nutr 2003;77:883–90.[Abstract/Free Full Text]
3. Gurson CT, Saner G. Effects of chromium supplementation on growth in marasmic protein-calorie malnutrition. Am J Clin Nutr 1973;26:988–91.[Abstract]

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