On top of fridges, stacked in grocery aisles, and sprinkled all over your social feed—protein powder is everywhere. You might even have a half-used tub quietly judging you from the back of your pantry. But what is protein powder, really? Protein powder is a concentrated source of protein made from animal or plant ingredients—like whey, casein, soy, pea, egg, or blends. The best protein powders deliver a potent dose of high-quality protein,  » Read more about: Guide to Protein Powder: Scoop the 411 From an RD  »