Nitrogen utilization, enzyme activity, glucose intolerance and leukocyte chemotaxis in human experimental zinc depletion.

We previously reported significant decreases in plasma, whole blood, urinary, seminal and fecal zinc in six young men consuming a semipurified formula diet providing 0.28 mg zinc and 0.8/kg protein per day for 4-9 weeks. During a one-week baseline period, 15.7 mg of zinc (as ZnSO4) were fed; three of the men were repleted with 6.0, 23.2 or 46.3 mg zinc for 2-5 weeks. Biochemical and functional measures of zinc status other than tissue zinc levels were also monitored. No one parameter appeared to parallel dietary zinc status in all subjects, although significant mean changes were seen in serum and leukocyte alkaline phosphatases. Inconsistent changes were noted in erythrocyte delta-amino levulinic acid dehydratase, plasma alkaline ribonuclease and the serum alkaline phosphatase isoenzymes. Nitrogen balance was unaffected by zinc nutritional status. However, alterations in hair root growth phase and morphology, decreases in lymphocyte counts and in transferrin levels during depletion suggest impairment in protein synthesis. Impaired leukocyte chemotaxis and clinical signs indicative of decreased resistance to infection were also noted.

Marginal malnutrition and reduced physical work capacity of migrant adolescent boys in Southern Brazil.

We measured the effect of marginal malnutrition on physical work capacity of adolescent children of agricultural migrant workers in Southern Brazil. Nutritional status was evaluated using 24-h dietary recall. Body size was evaluated anthropometrically. Biochemical assessments were also made. Physical work capacity (PWC170) was assessed by measuring heart rate, blood lactic acid levels, and oxygen consumption during submaximal bicycle ergometer work. The same tests were also carried out on a comparable group of local well-to-do boys of the same age in the same community who served as controls. The dietary results suggest that adolescent boys of migrant families were marginally malnourished. Their physical growth and development were retarded by at least 1 yr. They had significantly lower reserves of body fat and less muscle mass when compared with controls. Their Hb levels were normal. At the submaximal work loads measured (0, 25, 50, 75 W) the migrant children exhibited similar oxygen consumption and gross exercise efficiency as the control children, but achieved this work at a higher percentage of their maximum work capacity as shown by significantly higher heart rates for the same oxygen consumption. Higher blood lactic acid levels in the migrant children suggest that the available muscle mass was under greater stress to accomplish the same task. PWC170 was reduced one-third in the migrant children (migrant 643 +/- 162 kpm/min, control 905 +/- 345 kpm/min; p less than 0.005). These differences were largely associated with weight (migrant 20.6 +/- 5.9 kpm/min; control 18.8 +/- 4.3 kpm/kg/min; p greater than 0.1). These observations suggest that marginal as well as severe malnutrition affect physical work capacity at levels low enough to affect growth and development.

Energy expenditures and food intakes of lactating women in Guatemala.

Total energy expenditures and intakes were simultaneously assessed in 18 free-ranging lactating women (10 months postpartum) and compared to six similarly-sized, nonlactating, nonpregnant but multiparous women living in the same rural villages in the Guatemalan highlands. Energy intakes were estimated by the 24-hr recall method for each of 4 consecutive days. Energy expenditures were determined for 2 days by monitoring heart rate throughout the day and relating heart rate to oxygen consumption by individually-determined regression lines. The mean energy intake for the 4 consecutive days was estimated to be 1929 +/- 360 kcal/day (39.2 kcal/kg per day) for the lactating group; and 1876 +/- 404 kcal/day (38.3 kcal/kg per day) for the nonlactating group. The 2-day mean energy expenditures were estimated to be 2007 +/- 292 kcal/day for the lactating women (41.8 kcal/kg per day) and 1966 +/- 382 kcal/day for the lactating women (40.1 kcal/kg per day). The way of life of both groups was judged "moderately active" by 1973 FAO/WHO classifications. Most of the lactating women had been losing weight progressively during the past 6 months. Over the 10-week period prior to our measurnth) (P less than 0.01) than in the nonlactating group (-35 g/month) (ns). The high correlation (r = 0.87) between weight loss and the reduction in the sum of the three skinfolds suggested adipose tissue loss. There were no significant differences between the two groups in terms of daily energy intake, daily energy expenditure, the energy cost of specific activities throughout the day. The slope of the heart rate/oxygen consumption regressions suggest adequate cardiorespiratory fitness. This study suggests that the energy cost of lactation was met to a greater extent by fat loss than by either increased energy intake, reduced energy expenditure, or both.

PIP: Total energy expenditures and intakes were simultaneously assessed in 18 lactating women (10 months postpartum) and compared to 6 similarly-sized nonlactating, nonpregnant but multiparious women living in the same rural villag in the Guatemalan highlands. Energy intakes were estimated by the 24-hour recal method for each of 4 consecutive days. Energy expenditures were determined for 2 days by monitoring heart rate throughout the day and relating heart rate to oxygen consumption by individually-determined regression lines. The mean energy intake for the 4 consecutive days was estimated to be 1929 + or 360 kcal/day (39.2 kcal/kg/day) for the lactating group and 1876 + or - 404 kcal/day (38.3 kcal/kg/day) for the nonlactating group. The 2-day mean energy expenditures were estimated to be 2007 + or - 292 kcal/day for the lactating women (41.8 kcal/kg/day) and 1966 + or - 382 kcal/day for the nonlactating women (40.1 kcal/kg/day). The way of life of both groups was judged as moderately active by 1973 FAO/WHO classifications. Most of the lactating women had been losing weight progressively during the past 6 months. Over the 10-week period prior to our measurements, the mean weight loss was more than 10 times greater in the lactating group (-369 g/month) (P 0.01) than in the nonlactating group (-35 g/month) (ns). The high correlation (r=0.87) between weight loss and the reduction in the sum of 3 skinfolds suggested adipose tissue loss. There were n significant differences between the 2 groups in terms of daily energy intake; daily energy expenditure; energy cost of specific activities; or in the pattern of activites during the day. The slope of the heart rate/oxygen consumption regressions suggest adequate cardiorespiratory fitness. This study indicates that the energy cost of lactation was met to a greater extent by fat loss than by either increased energy intake, reduced expenditure, or both.

Sulphate, acid-base, and mineral balances of obese women during weight loss.

Four obese women, each at least 50% above their expected weight for height were maintained in the metabolic unit for 63 days on liquid formula diets of differing protein and calorie content. We made the following findings: 1) When 12 g protein nitrogen was consumed, 1 mEq of acid was excreted in the urine for every 2 mEq of urinary sulphate. 2) On a protein-free diet more acid was excreted in the urine than could be accounted for by oxidation of sulphur to the sulphate which was excreted in the urine. 3) Both increased consumption of protein and a restriction of dietary calories was associated with an increase of urinary acid. 4) Urinary sulphur excretion was closely correlated with nitrogen intake and urinary urea nitrogen excretion. However, on a protein-free diet the ratio of total nitrogen to sulphur in the urine was greater than when 12 g protein nitrogen was consumed. 5) There is some evidence that when total calorie intake was reduced at a level of 12 g protein nitrogen intake, the ratio of urinary urea nitrogen to urinary sulfur decreased. This suggests selective retention of some nonsulphur containing amino acids and/or selective oxidation of sulphur-containing amino acids. 6) In general, urinary calcium and magnesium excretions were depressed both with a decrease in protein consumption and a decrease in caloric intake. 7) The urinary excretions of calcium and magnesium showed a tendency to fall during the 63 days of the experiment. 8) The urinary and fecal phosphorus excretion remained constant during the various metabolic periods of the experiment.