The effects of sweat nitrogen losses in evaluating protein utilization by preadolescent children

Abstract

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.

Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults

“…As shown in Figure 1, dermal losses differed significantly depending on the climate under which the study was conducted; therefore, we analyzed the data from the 2 climatic regions separately. A summary of the average dermal and miscellaneous nitrogen losses obtained in each study [excluding those individual data points reported by Calloway et al (86) Because it has often been reported that dermal nitrogen losses are directly related to nitrogen intake (45,86,88,91,92), we alternatively used analysis of covariance to estimate separate regression equations for the response of dermal (plus miscellaneous) nitrogen losses as a function of nitrogen intake within each of the 2 climatic regions. We found a significant (P = 0.006) response curve for the temperate studies only: On the basis of these analyses, we adjusted the nitrogen balance data for each study by 1) the measured dermal losses, if available (with the use of additional 1.77 mg N for miscellaneous…”

“…Millward and Roberts (8), in their review of the literature, concluded that a value of ≤ 5 mg N • kg Ϫ1 • d Ϫ1 would be more appropriate. Studies in infants (103) and preadolescent children (91,92) suggest that dermal or sweat nitrogen losses are Ϸ10 mg • kg Ϫ1 • d Ϫ1 , or more, and that they vary with the nitrogen intake (91,92,104). Because the rate of nitrogen loss via the skin varies significantly, as does body surface area, we chose to use only data from adults to estimate a suitable allowance for dermal and miscellaneous losses.…”

Dietary Reference Intakes for Japanese 2010: Protein

“…This was the mean value obtained by multiple nitrogen balance studies on growing subjects, including children and adolescents (34)(35)(36)(37)(38)(39)(40). Regarding miscellaneous nitrogen losses other than that in feces and urine, the value of 6.562.3 mgN/kg body weight/d (range, 5-9 mgN/kg body weight/d) obtained in current reports (34,(41)(42)(43)(44), was adopted. The same value adopted for the protein maintenance requirement was used in all age groups composed of growing subjects, since there was no evidence to suggest any differences among these age groups.…”