Technical Abstract: The in vitro binding of bile acids of milled wheat bran (MWB) and milled extruded wheat bran (MEB) at five specific mechanical energy (SME) levels of 120 (MEB-120), 177 (MEB-177), 234 (MEB-234), 291 (MEB-291), and 358 (MEB-358) Wh/kg on dry weight basis, was determined using a mixture of bile acids secreted in human bile at a duodenal physiological pH of 6.3. Relative to cholestyramine (bile acid binding, cholesterol-lowering drug) in vitro bile acid binding capacity on dry matter (DM), total dietary fiber (TDF) and insoluble dietary fiber (IDF) basis was for MWB: 21, 43, 45%; the values for MEB ranged 18-21%, 34-41% and 36-43%, respectively. MWB resulted in significantly higher bile acid binding than that for MEB at 120, 234 and 291 Wh/kg on DM, TDF and IDF basis. These results demonstrate the relative health-promoting potential of MWB = MEB-177 = MEB-358 > MEB-120 = MEB-234 = MEB-291 as indicated by their bile acid binding on DM basis. Data suggest that significant improvement in health-promoting (cholesterol-lowering and cancer-preventing) potential could be obtained in WB by milling (low-cost processing) the bran to finer particle sizes and extruding (high cost technology). MWB did not further enhance its healthful potential. Milling WB to small particle size (weighted mean 0.508 mm) may have induced changes in the physical and chemical characteristics of WB and/or created new linkages, binding sites of the proteins, starches, and non-starch polysaccharides, which significantly increased the bile acid binding ability of the MWB. Specific changes in chemical composition as a result of reducing the particle size (weighted mean 1.018 mm to 0.508 mm) as they relate to bile acid binding potential will be explored in future studies.