Dietary sulfur amino acids and genetic make-up or interindividual variation affect the response of men to copper deprivation

An experiment was performed to ascertain whether factors other than dietary copper, specifically the sulfur amino acids cystine and methionine, affect the extent and nature of copper deprivation signs. Ten men aged 19 to 39 years were housed in a metabolic unit and fed high methionine (2.4 g/2,500 kcal) diet that supplied 0.6 mg Cu and 0.7 g cystine/2,500 kcal. After an equilibration period of 15 days during which the basal diet was supplemented with 0.7 mg Cu and 1.0 g cystine/day, all men participated in four dietary periods of 36 days. In these periods, supplements of copper (0.0 and 2.0 mg/day) and cystine (0.0 and 2.0 g/day) were varied in a 2 .times. 2 factorial design. Results including all subjects revealed only a few significant changes; one of these was a depression in serum enzymatic ceruloplasmin with copper deprivation. However, the subjects seemed to separate into two groups; this separation could be based upon the response of serum cholesterol to copper deprivation with the high cystine diet. If these two groups were examined separately, copper deprivation altered several indicies associated with copper metabolism or function; these included serum total and LDL-cholesterol, erythrocyte superoxide dismutase, mononucleated white cell cytochrome-C oxidase, and whole blood glutathione. Moreover, dietary cystine affected the response of some of these variables to copper deprivation. Surprisingly, the responses of the two groups were often opposite of each other. If one group showed an increase in a variable in response to copper deprivation, the other group showed a decrease, or vice versa. These contrasting differences most likely were the result of differences in genetic make-up or interindividual variation, or in prior dietary habits and environmental exposures. These differences could have led to a different physiological make-up which responded differently to short-term dietary copper deprivation. The findings indicate that signs of copper deprivation can be induced in adult humans. Although the signs are variable, their nature suggests that copper is of nutritional concern.