Effects of large variations in diet on free catecholamines and their metabolites in urine

Abstract

Urinary excretion of free catecholamines and their major metabolites was studied in seven normal young men while they were on three diets which were excessive, moderately restricted, or very low in catecholamine nad caffeine content. When results are expressed in relation to urinary creatinine, the most liberal diet increased normetanephrine ( NM) and VMA excreation by about 30 per cent. Free epinerphrine ( E) and metaphrine ( M) excretion rates also increased by 40 per cent and 10 per cent, respectively, but the changes were not statistically significant. Changes in free norepinerphrine ( NE) and free dopamine ( D) excretion were small and did not approach statistical significance. When results are expressed as quantities excreted per day, the only statistically significant differene associated with diet was greater excretion of M during the moderately restricted diet. Intra-subject variation in estimated excretion and creatinine was arge, with a median coefficient of variation of 16 per cent. When amines and metabolites were expressed per unit of creatinine, intrasubject variance of metabolites was made smaller but variance of free amines was not. This “creatinine correction” tended to enhance the statistical significance of intersubject differences. The more liberal diets tended to increase intrasubject variance, particularly of E and NM. Variance of NE was least affected. Except for E and NM, where it was roughly equal to diet effects, intersubject variance was much greater than the diet effects. It is concluded that in studies of urinary NM and VMA, attention must be given to the NE content of the diet. In studies involving E and M, caffeine shoudl be proscribed or controlled. In the case of free NE, and probably of free D, no control appears to be necessary.