A study of plasma free amino acid levels. V. Correlations among the amino acids and between amino acids and some other blood constituents

Possible relationships among the amino acids were examined by determining the correlation between their fasting plasma levels in 136 children and 193 adults. Leucine and isoleucine values were the most highly correlated. Threonine, serine, and glycine were significantly related in boys, girls, and men, but there was no correlation between threonine and glycine levels in women. A group of 11 amino acids appeared to be highly interrelated: These were alanine, asparagine, glutamine, valine, isoleucine, leucine, methionine, tyrosine, phenylalanine, proline, and lysine. Possible correlations between the individual amino acid levels and hemoglobin, blood glucose, plasma cholesterol, and uric acid levels were also examined. There were no highly significant relationships between amino acid levels and the levels of any of them.