Table I. Mineral Element Content of Ten Kinds of Raw, Mature, Dry Legumes' mg/100 g edible portion Kind of legume Calcium Copper Iron Magnesium Manganese Phosphorus Potassium Sodium Zinc Phaseolus vulgaris Navy beans 135.5 ± 2.0 0.80 ± 0.02 5.34 ± 0.02 162.8 ± 2.3 1.02 ± 0.01 453 ± 6 820.8 i 15.0 1.66 ± 0.03 2.17 i 0.04 Great northern beans 181.2 ± 2.9 0.82 ± 0.02 6.87 ± 0.08 178.3 ± 4.7 1.52 ± 0.02 458 ± 3 1087.3 ± 21.1 3.60 ± 0.04 2.12 i 0.04 Pinto beans 111.7 ± 3.6 0.67 ± 0.06 7.04 i 0.15 170.8 ± 7.9 1.52 ± 0.13 510 ± 69 1156.2 ± 43.4 2.51 ± 0.10 2.21 t 0.05 Red kidney beans 59.5 t 2.6 0.69 * 0.01 7.47 ± 0.23 123.0 ± 5.1 1.43 ± 0.10 374 ± 13 1300.7 ± 11.7 2.45 ± 0.03 2.52 ± 0.04 Signif. of diff.b

Three lots each of ten kinds of mature dry legumes were purchased in the Virginia market. Subsamples of each lot were analyzed for proximate components before and after cooking by standard household procedures. Data on yields of cooked legumes were obtained for both weight and volume measures. Lentils had the highest ratio of cooked weight to dry weight, 2.94, and chickpeas had the lowest ratio, 2.07. Protein, fat, and ash values were generally in good agreement with data tabulated in Agriculture Handbook 8, but moisture data were higher, and crude fiber values were much higher than data in Handbook 8. Analyses of variance showed significant differences among four kinds of Phaseolus vulgaris beans for all proximate components except crude fiber in cooked beans. Significant differences between baby and large lima beans were found for most proximate components, although for cooked lima beans these differences were nutritionally unimportant.

A nitrogen balance study was conducted to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess further the impact of sweat nitrogen on protein needs of preadolescent children. Values were determined through the collection of 24-hr, total body sweat samples from twelve healthy boys having a mean age of 8 years, 8 months. Mean height and weight of the subjects were 131.4 cm and 31.0 kg, respectively. Environmental conditions were relatively constant during the study. Mean sweat nitrogen losses were 208, 287, and 368 mg/day on daily protein intakes of 29, 54, and 84 g, respectively. Mean nitrogen balances per day were 0.39, 0.09, and 1.95 g when sweat nitrogen losses were included in the calculations. At the lower and moderate levels of protein intake, nine and six subjects were in negative nitrogen balance when sweat losses were considered. Sweat nitrogen losses in the boys were similar to a previous study with preadolescent girls. Based upon published basal metabolic rates and mean sweat nitrogen losses of 261 and 288 mg/day for girls and boys, the nitrogen lost through sweat was 0.25 mg/basal kcal for both sexes. An estimation of 0.5 mg/basal kcal for integumental nitrogen loss appears realistic for this age group.

The effects of zinc intake on nitrogen utilization was investigated during a 20-day balance study with 23 preadolescent girls. The children were fed a diet which provided 4.17 g of nitrogen and 5.5 mg of zinc daily; the diet was supplemented with a combination of 5 mg of zinc and/or nitrogen supplied from either amino acids or nonspecific nitrogen. Complete collections of excreta were made throughout the study. Neither the supplementation of amino acids nor zinc improved the retention of nitrogen. Urinary excretion of urea nitrogen, uric acid, and creatinine were not different as a result of zinc supplementation. Subjects consuming the lower level of zinc were in negative zinc balance, but the subjects consuming 10.5 mg of zinc were in positive balance. The supplementation of this low protein diet with amino acids did not improve nitrogen retention.

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