Heritability of plasma amino acid levels in different nutritional states.

Significant heritability has been shown for several plasma amino acid levels, but the results may have been confounded by sampling in a variety of nutritional states. We studied a group of families on a low protein steady-state diet in fasting and non-fasting states. Heritability of individual amino acids varied according to the nutritional state, suggesting the amount of genetic and environmental influences differ among the operative systems that control individual amino acid homeostasis throughout the feed/fast cycle.