You can buy Ades soy milk, which is similar to Silk in the US. It's a processed food, but it's soy milk. You can also buy fresh plain soy milk at any Chinese store. Barrio Chino is your best bet and we have one right behind our house in Congreso. Diateticas are a strange name for health food stores, but that's what they are and they sell lots of things. You can buy organic whole grain breads and other things, deserts, empanadas, flours, at Hausbrot which has several locations around the city, high quality, delicious food, very affordable. There is an organic farmer's market across from the front gate to Chacarita cemetery, next to the train/subte station. It's very good, though far, a bit pricey, but they have cheeses, meats, fruits and vegetables and it's all in one place...