WHOLE-BODY PROTEIN-TURNOVER IN HUMANS FED A SOY PROTEIN-RICH VEGETABLE DIET

Objectives: This study was designed to compare the whole-body protein turnover in humans after the ingestion of a soy protein-rich vegetable diet with that of a control group fed a western animal protein-rich d iet. Subjects: Twelve male volunteers were divided into two groups of six subjects who were given for two weeks either a 85% vegetable prote in diet (diet VP) or a control western animal protein-rich diet (diet PLP). Interventions: Whole-body protein turnover was estimated at the end of the two-week controlled diet period using the [N-15]-glycine en d-product method. Nitrogen flux rates were determined in the fed state (1,3 g protein/ kg) over a 9 h period after the dose of [N-15]-glycin e was given. Results: After the 9 h of the test. the urinary ammonia e xcretion was significantly higher in the group receiving the diet AP t han that in the group receiving the diet VP (P < 0.05). In contrast, t here was no significant difference for both total nitrogen and urea ni trogen excretions. Both the protein synthesis and the protein breakdow n were similar in both groups. In the same way, the net protein deposi tion measured in the fed state during 9 h was similar for both diets a t 0.07 g/kg/h. Conclusions: Young adults fed 1.3 g/kg/d of either meat or vegetable protein-rich diet for two weeks did not show a different protein turnover.