Whey protein powder is made from milk, so it does contain lactose, but not a significant amount. Comparatively, whey contains a lot less lactose than other dairy foods like milk, yogurt, cottage cheese, and ice cream. People with lactose intolerance, a common digestive problem which may cause bloating among other symptoms, may or may not have trouble digesting whey protein. And, depending on how it has been filtered, some whey protein powders contain a little lactose while others have none. For people who lack the digestive enzyme lactase (which breaks down lactose) or who have a sensitivity to lactose, a whey protein isolate is often the best whey choice. For people who are highly sensitive to lactose, and vegans or dairy-free eaters who are seeking a 100% non-lactose protein powder, see our review of the Best Vegan Protein Powders where we share our top picks for powders featuring brown rice, pea protein, and other plant-based protein sources.