Effect of variable protein intake on whole-body protein turnover in young men and women.

The effect of the amount of protein intake (12% and 21% of total energy intake, diet A and diet B, respectively) on nitrogen balance and whole-body protein turnover (PT) was measured in 19 young men and 10 young women (aged 30 +/- 5 and 27 +/- 4 y, respectively). In young adults, mean nitrogen balance was approximately zero during diet A whereas it was positive during diet B. In young adults, PT was significantly higher during diet B in comparison with diet A. This was also seen in elderly subjects, as described before. From a comparison of the current data with the data previously obtained in elderly subjects it can be concluded that during diet A young adults had PT rates higher than those of elderly subjects. During diet B, PT of young men was comparable with the PT of elderly men whereas young women still had higher PT rates than elderly women (even when corrections were made for differences in body composition).