Prediction of human dietary δ\u3csup\u3e15\u3c/sup\u3eN intake from standardized food records: Validity and precision of single meal and 24-h diet data

Natural stable isotope ratios (δ15N) of humans can be used for nutritional analyses and dietary reconstruction of modern and historic individuals and populations. Information about an individual’s metabolic state can be obtained by comparison of tissue and dietary δ15N. Different methods have been used to estimate dietary δ15N in the past; however, the validity of such predictions has not been compared to experimental values. For a total of 56 meals and 21 samples of 24-h diets, predicted and experimental δ15N values were compared. The δ15N values were predicted from self-recorded food intake and compared with experimental δ15N values. Predicted and experimental δ15N values were in good agreement for meals and preparations (r = 0.89, p \u3c .001) as well as for the 24-h diets (r = 0.76, p \u3c .001). Dietary δ15N was mainly determined by the amount of fish, whereas the contribution of meat to dietary δ15N values was less pronounced. Prediction of human dietary δ15N values using standardized food records and representative δ15N data sets yields reliable data for dietary δ15N intake. A differentiated analysis of the primary protein sources is necessary when relating the proportion of animal- derived protein in the diet by δ15N analysis

Total hemoglobin mass, iron status, and endurance capacity in elite field hockey players

The aims of this study were as follows: To evaluate total hemoglobin mass (tHbmass) in international field hockey players; to examine the correlation between tHbmass and maximum oxygen uptake (VO2max); and to assess influences of iron status on tHbmass and on VO2max. The players of the German women's (N = 17, aged 24.8 +/- 3.0 [21-31] years) and men's (N = 17, aged 24.2 +/- 2.9 [19-32] years) national field hockey team were investigated. tHbmass was measured by an optimized carbon monoxide rebreathing method. The following parameters were measured in venous blood: Hemoglobin concentration (Hbconc), hematocrit (Hct), number and percentage of reticulocytes, reticulocyte hemoglobin content, serum iron, serum ferritin, serum transferrin, unsaturated iron-binding capacity, and serum soluble transferrin receptor concentration. VO2max was determined in a treadmill test. tHbmass (women: 10.6 +/- 1.1 g/kg; men: 12.5 +/- 0.9 g/kg) correlated to VO2max (women: 46.6 +/- 2.9 mL/min/kg; men: 55.8 +/- 4.0 mL/min/kg) in women (r = 0.56, p < 0.05) and in men (r = 0.57, p < 0.05), whereas Hbconc and Hct did not. The investigated parameters of iron status showed no association to tHbmass or to VO2max. In conclusion, tHbmass can be used as an indicator for endurance capacity in elite field hockey players, whereas Hbconc may not. tHbmass or VO2max were not influenced by the actual iron status of the investigated athletes