A study of plasma free amino acid levels. II. Normal values for children and adults

Mean values for the fasting plasma levels of the individual amino acids are given for 136 children (aged 6–18 yr) and 194 adults. There are statistically significant differences between the mean values of boys and girls for only a few amino acids, but there are highly significant differences between the values for men and women for most of the amino acids. Men have higher levels than women for all the amino acids except glycine, serine, and threonine. Charts showing the mean values and variances of the amino acid levels of children and of men and women have been prepared. These allow a convenient medium on which to plot plasma amino acid analyses for easy detection of abnormal blood levels.