Legumes (peas, lentils, chickpeas, garbanzo beans) are protein-and fiber-rich plants used heavily in grain-free pet food as substitutes for traditional grains. They're nutritious in moderation but raise concern when they dominate the first five ingredients — a pattern associated with the FDA's DCM investigation in dogs. Legumes also contribute plant proteins that don't substitute well for animal proteins from a bioavailability standpoint.