The definition of "natural" is subjective and can vary, but in general, protein powder is considered a processed food. Most protein powders are derived from natural sources, such as milk (whey protein), peas (pea protein), or rice (rice protein), but the process of extracting the protein and turning it into a powder form involves multiple steps and the addition of other ingredients, such as sweeteners, flavors, or thickeners.
Therefore, some people might consider protein powder to be natural, while others may view it as a highly processed food. If you're concerned about consuming only natural ingredients, you may want to choose a protein powder that has a simple, straightforward ingredient list and minimal processing. You may also want to choose a plant-based protein powder, as these tend to have fewer additives and processing compared to animal-based protein powders.