Original Paper Ann Nutr Metab 2001;45:19–23 Protein Quality Evaluation in Rats of Typical Diets for 4- to 6-Year-Old Children from Different Socioeconomic Areas Living in Oaxaca, Mexico C. Jane Wyatt a M.A. Triana Tejas b R.O. Méndez a M.E. Valencia a a Department of Human Nutrition, Centro de Investigacio ´ n en Alimentacio ´ n y Desarrollo, Hermosillo, Sonora and b Instituto Tecnolo ´ gico de Oaxaca, Oaxaca, México Received: April 13, 2000 Accepted: October 2, 2000 C. Jane Wyatt CIAD, Apartado Postal 1735 Hermosillo, Sonora (Mexico) Fax +52 62 80 00 94 E-Mail jwyatt@cascabel.ciad.mx ABC Fax + 41 61 306 12 34 E-Mail karger@karger.ch www.karger.com © 2001 S. Karger AG, Basel 0250–6807/01/0451–0019$17.50/0 Accessible online at: www.karger.com/journals/anm Key Words Protein quality W Beans and corn tortillas W Rats W Protein digestibility Abstract Legumes and cereals are principal sources of energy and protein in developing countries. In Oaxaca, Mexico, corn is the primary agricultural crop, therefore corn tortillas and beans are the main energy and protein sources. The objective of this study was to evaluate the protein quality in rats of typical diets for 4- to 6-year-old children from different socioeconomic areas in Oaxaca, Mexico. Com- posite diets representing the typical diets were formu- lated and fed to male weanling rats for 10 days. A control diet using casein as the reference diet and one free of nitrogen were included in the study. The apparent pro- tein digestibility was determined in rats using the chromic oxide marker technique and the data was statis- tically analyzed for differences between control and ex- perimental diets. Rats fed the diet of low income children gained about 2 g/day compared to about 3.8 g/day for the rats fed the control (casein) diet and had the lowest weight gain/g of protein intake. The NPR was 3.52 com- pared to 4.31 for the control diet. This diet is 67% vegeta- ble protein and 33% animal protein. The diet for the medium income group contained a higher percentage of animal protein, 76% and thus higher digestibility, 78%. The results of this study indicate that the protein quality of children’s diets in Oaxaca, Mexico, need to be im- proved. Copyright © 2001 S. Karger AG, Basel Introduction In developing countries, legumes and cereals are the principal energy and protein sources in the diet. Lack of adequate food and in particular high-quality proteins, is the primary cause of malnutrition in children which causes retarded growth. In Oaxaca, Mexico, corn is the primary agricultural crop, therefore corn tortillas are the main energy source. Studies have shown that the combi- nation of legumes and cereals, if done properly, can pro- vide a diet of good protein quality [1, 2]. The diet for low income children, 4–6 years old, has been characterized according to income status [3]. Oaxaca is one of the poor- est regions in Mexico where income available for food is low [4]. A study by Triana et al. [5], using the Waterlow classification system, showed 28.8% of the pre-school