Abstract
It has been suggested that a low protein intake causes sustained enhancement of sympathetic nervous activity. Thus, the present study was undertaken to see the effects of different sizes of protein intake under a constant daily energy intake (1,600 kcal/day), on urinary excretions of catecholamines and their metabolite, vanylmandelic acid (VMA), in healthy young women. In the experiment 1, in which 40g- and 80g-protein containing food were taken for 4 days and 8 days, respectively, VMA excretion decreased after 80g-protein intake. In the second experiment, 40g-, 80g-and 40g-protein containing food were successively taken for 4 days, respectively. In here, dopamine (DA) excretion increased significantly after 80g-protein intake, and returned to the initial level by retaking of 40g-protein containing food. Noradrenaline (NA) excretion did not change after 80g-protein intake. NA/DA ratio decreased significantly after 80g-protein intake, and returned to the initial level after the second 40g-protein intake. VMA excretion tended to decrease successively during the 80g-and the following 40g-protein intake periods. The present results indicate that the conversion of DA to NA may be suppressed by a excess protein intake, and that the enhanced sympathetic nervous activity observed in the lean subjects, could be caused, at least in part, by a lower protein intake by them.
