Zinc, copper, and manganese intake and balance for adults consuming self-selected diets

Twenty-eight adult men and women participated in a year-long study designed to determine accurately the nutrient intake of adults who lived at home and consumed self-selected diets. During four metabolic balance periods, 7 days each, corresponding to the seasons (spring, summer, fall, winter), duplicates of the diet, and all urine and feces were collected. Daily mean intakes for zinc and copper were 9.9 and 1.2 mg, respectively. These levels were less than the recommended daily intakes of 15 mg for zinc and 2 to 3 mg for copper. In contrast, the mean dietary intake of manganese was 3.0 mg/day which is within the suggested safe and adequate range of 2.5 to 5.0 mg. Metabolic balances were negative for all three elements possibly due to a reduction in food intake during the collection periods compared to the noncollection intervals. The collection of the duplicate diets apparently influenced the food intake during the collection weeks.