The results showed that soaking decreased total phosphorus (TP) in the range of 35–92.4 mg/100 g compared to 255 mg/100 g in whole rice. The losses of phytate in the grains were between 87 and 91%, the remnant phytic acid phosphorus in the grains being between 15.1 and 20.9 mg/100 g, and the most effective treatment was soaking at 45 °C for 48 h. The losses of the different nutrients were high in all of the different soaking treatments, reaching 50% for Fe, more than 64% for Zn, and around 45% for proteins. Although protein digestibility and mineral dialyzability were improved, acid soaking of brown rice would not be suggested as a useful process to reduce phytates from whole rice grains, if the production of a staple food is the main objective.