Circulating zinc concentrations were measured in 73 healthy adult males and females 19-52 years of age who were volunteers for eight different metabolic studies at the University of California, Berkeley. The interindividual variation in the eight studies varied from 5 to 20%; the global coefficient of variation for all studies was 12 +/- 7% (mean +/- SD). The analysis of a reference plasma sample on six different days showed a mean coefficient of variation of 3.8%. Thus, only a small portion of the intraindividual variation is due to day-to-day analytical differences. There was no relationship between circulating zinc concentrations and age, height, or body mass index. Nor were there any significant differences due to gender. Information regarding dietary zinc and protein intakes was available from three-day weighed food intake records from 44 of the subjects. Plasma zinc concentrations were unrelated to the intake of either zinc or protein in those subjects. The results of this study show that the impact of age, gender, body size and dietary zinc or protein on circulating zinc concentrations are too small to be detected in the presence of the analytical and endogenous factors that influence plasma/serum zinc concentrations. Also, within a population of healthy adults, circulating zinc concentrations may vary by as much as 15%.
The study was designed to determine if the activity pattern of pregnancy women on an intake of energy lower than that recommended will affect fetal growth. Subjects who volunteered were either attending public or private hospitals. Pregnant women in the "private" group were significantly older (p < 0.001) weighed somewhat less and significantly taller (p < 0.001) when compared to the "public" group. Differences in energy intake during the second and third trimesters between the "public" and "private" groups were small; 1608 +/- 334, 1726 +/- 271 kcal and 1627 +/- 367, 1778 +/- 260 kcal, respectively. However, daily activity patterns revealed that the "public" group was more active as reflected by the higher energy expenditure of 1412 +/- 74 kcal and 1578 +/- kcal during the second and third trimesters respectively. There was a significant difference (p < 0.01) in birth weight between the "public" and "private" groups; 2951 +/- 377 g and 3173 +/- 357 g respectively. This study indicates that energy intakes lower than recommended and sedentary lifestyles have no direct influence on birth weights of babies.
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