The effect of consumption of unprocessed and processed oat bran on calcium, magnesium, zinc, and copper intake, excretion and apparent retention in 19 adult males was determined using a metabolic balance study. The study was divided into preliminary, controlled feeding and follow-up periods of 4 weeks each. The controlled feeding period was subdivided into two 8 day balance periods. Subjects were randomly assigned to one of three treatments: a basal diet low in dietary fiber; basal diet supplemented with 100 g of unprocessed oat bran; or basal diet supplemented with 100 g of processed oat bran ready-to-eat (RTE) cereal. With both oat bran treatments intakes of calcium, magnesium, and copper were increased above the current RDA, while zinc was increased, but still remained below the RDA. Urinary excretions of calcium, magnesium, and zinc were unchanged during the balance periods. Both of the bran supplemented groups were excreting significantly more fecal magnesium and zinc than the control group. Increased fecal calcium and copper excretions were seen for the processed (RTE) group over the other two treatments. Apparent retention of calcium, zinc, and copper appear to be unaffected by oat bran supplementation. Apparent magnesium retention for the control group was significantly less than the unprocessed group during balance Period 1 only. During the controlled feeding period, the unprocessed group had significantly less plasma calcium and zinc than the other two treatments. Plasma magnesium was unchanged in the fiber supplemented groups during the controlled feeding period. / Master of Science