Pre-breakfast plasma zinc concentrations: the effect of previous meals.

The aim of this study was to determine the effect of the time and size of the last meal of the previous day on pre-breakfast 0700 hours plasma zinc concentrations. Nine healthy women were each studied on four separate occasions when the same standard meal was taken either at 1800 hours (study 1); double meal at 1800 hours (study 2); at 2400 hours (study 3); or at 1800 hours and 2400 hours (study 4). Mean differences between 1800 hours (day 1) and 0700 hours (day 2) plasma zinc (mumol/L +/- SEM) were 1.6 +/- 0.3 for study one; 0.8 +/- 0.3 for study two; 0.1 +/- 0.3 for study three and 0.0 +/- 0.2 for study four. The differences for studies two, three and four were significantly less than the difference for study one (p less than 0.05). The difference for study four was also less than the difference for study two (p less than 0.05). Changes in time and size of the meals accounted for 59% of within-subject variation in 0700 hours plasma zinc concentrations. It is concluded that pre-breakfast 0700 hours plasma zinc concentrations are affected by the time and the size of the meal(s) consumed the previous evening.