Serum zinc and copper during long-term total parenteral nutrition

Changes in serum zinc and copper levels were studied in 17 patients who received 18 courses of total parenteral nutrition for 28 to 89 days. Mean serum zinc levels decreased significantly after 4 weeks of therapy in the group without zinc supplementation when compared with pretreatment levels (p less than 0.05) and in a second group who received about 1.5 mg of zinc per day (p less than 0.05). Serum copper levels fell consistently and significantly in patients of both groups. However, no obvious clinical signs or symptoms of zinc or copper deficiencies were observed. Blood transfusions were not able to significantly change the serum levels of zinc or copper. Although serum alkaline phosphatase has been suggested as a functional indicator of zinc deficiency, the concomitant hepatic or skeletal dysfunction of the patients made its interpretation difficult. These findings indicate that a decrease in serum zinc and copper is common during TPN using solutions unsupplemented with these trace elements. Supplementation of TPN solutions with zinc, copper, and other trace elements is recommended.