There are a lot of options for protein powder. Of course, the first thing you should check is for any allergies to a specific brand. We generally like the Body Fortress brand of protein powder. I can get this from our local Walmart or I order it from Amazon. The price is about the same, so the last time we needed some I ordered online. Our store was completely out of vanilla and I don't know how the other flavors would taste in the smoothie. Since it's the only way we drink it, I didn't want to try something different right now.