Effects of a glandless cottonseed protein diet on fasting plasma amino acid levels in college women.

Plasma amino acids were determined and correlated to the level of dietary amino acids consumed over a 42-day period. Six college women, ages 19 to 23, were fed meals in which 99% of the dietary protein was supplied by glandless cottonseed flour. The protein content was decreased weekly from 14.6 to 9.9, 8.7, 7.5, 6.9, and 6.3 g nitrogen per day, until that amount was found that would not maintain nitrogen equilibrium. Fasting blood samples were obtained after subjects had consumed a specific protein level for 1 week. Significant (P less than 0.05) decreases in fasting plasma free amino acid levels occurred from day 0 to 7 of the study for threonine, proline, isoleucine, leucine, tyrosine, and lysine. There were no significant differences in these plasma amino acids thereafter. Of the essential amino acids, leucine, valine, histidine, and lysine appeared to have similar graphical trends between the plasma and dietary amino acid concentrations over the entire 6-week period. However, only leucine had a significant (P less than 0.05) correlation. Results indicated that fasting plasma free amino acid concentrations of young women on a cottonseed protein diet appear to drop initially, but rarely fall beyond the realms of normal values during nitrogen equilibrium.