[Comparison of 3 methods of evaluating the energy and nutrient content of diets]

A total of 83 diets served over a period of 20 days to hospitalized diabetic patients were studied. The diets were modified in both calories and carbohydrates and were prepared in a centralized cooking facility. The diets studied were randomly selected, without replacement, using a random number table. Quantities of food served were determined using the direct weighing method. The nutritional value of the diets was determined by three indirect methods. The first, the detailed method, using energy and nutrient values of individual foods, and two abbreviated methods, I and II, based on the reference food values and food group mean values. Calories, proteins, carbohydrate, calcium, phosphorus, iron, retinol, and thiamine, riboflavin, niacin, and ascorbic acid contents were calculated for each diet. Furthermore, for each of the energy and nutrient calculations, the mean, standard deviation and variance were determined for all diets. A correlation and linear regression study was performed, to establish differences between the detailed and the abbreviated methods. Also, Student's "t" test of equality of means was used to identify differences in the calculation of the nutrient content of the diets. Significant differences among the values obtained by the three methods were found. In relation to the values obtained by the abbreviated methods, significant differences were found only for calcium and thiamine. In general, however, the diet calculation using the abbreviated methods gave similar results as those obtained by using the detailed method. Therefore, the use of the abbreviated methods at hospital level is considered convenient because they considerably reduce work, time and costs of diet planning and evaluation, making them easier. Nevertheless, their limitations should be taken into account. The preceding results document substantial problems in the use of the two abbreviated methods studied. The differences observed between the detailed and abbreviated methods in mean levels of most nutrients are unacceptably large, suggesting that the abbreviated methods suffer biases in estimating the nutrient content in the hospital diets studied. These problems are particularly important for the diabetic patients who composed the sample, in that dietary energy, fat, and carbohydrates were over-estimated in a consistent manner by both abbreviated methods used. Nonetheless, abbreviated methods, such as those used in the present study, have advantages which cannot be ignored: they are easy to use, reducing time requirement, and conceptual simplicity.(ABSTRACT TRUNCATED AT 400 WORDS)