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Title: SHORT-TERM KINETICS OF ZINC METABOLISM IN WOMEN FOLLOWING A BREAKFAST MEAL

Author
item LOWE, NICOLA - UNIV OF CALIF BERKELEY
item WOODHOUSE, LESLIE - UNIV OF CALIF BERKELEY
item King, Janet

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Previous research done in our laboratory showed that plasma zinc concentrations drop 15-20% when meals are consumed. The purpose of this study was to determine if that decline in plasma zinc is due to an expansion of the plasma volume or to a redistribution of zinc from the plasma to the tissue. Nine women participated in two trials, a fasting and a breakfast meal trial; five of those women also participated in a third trial when the energy content of the breakfast meal was doubled. At each trial, a stable isotope of zinc was infused intravenously. The disappearance of the isotope from the plasma fit a two-compartment, or a two-pool, kinetic model. The postprandial decline in plasma zinc concentrations correlated with a decrease in the size of the first pool suggesting that plasma zinc was the primary constuient of that pool. The size of the second pool, thought to be located primarily in the liver, increased significantly after the doubled breakfast. In conclusion, this study demonstrates that the decline in plasma zinc concentrations following a meal is due to tissue zinc uptake, possibly to facilitate the assimilation and metabolism of food.

Technical Abstract: A stable isotope of zinc, **70Zn, was used to study the effect of a breakfast meal on plasma zinc kinetics. Nine women participated in two trials, a fasting and a breakfast meal trial; 5 of the women participated in a third trial in which the energy content of the breakfast meal was doubled. At each trial, **70Zn was infused intravenously, and the plasma disappearance of the isotope was analyzed using a two-compartment model of zinc kinetics. Plasma zinc concentration fell significantly following the two trials in which the subjects were fed meals, reaching a nadir of 13% and 19%, respectively, below the concentrations at comparable times during the fasting trial. The postprandial fall in plasma zinc concentrations correlated positively (r2=0.67) with a decrease in the size of the most rapidly turning over zinc pool (pool a), suggesting that pool a is composed primarily of plasma zinc. The second, more slowly turning over zinc pool (pool b), increased significantly (p<0.05) after the doubled breakfast meal. This increase in pool b was associated with a trend towards an increase in the fractional turnover of zinc from pool a to pool b. The results suggest that the decline in plasma zinc concentrations following a meal is due to a redistribution of zinc from the plasma to rapidly turning over pools involved in the assimilation and metabolism of fuels following food intake.