AFAA Personal Trainer Certification 2025 – 400 Free Practice Questions to Pass the Exam

The correct choice highlights that incomplete proteins are typically derived from plant sources. These plant-based proteins often lack one or more of the essential amino acids that the body cannot produce on its own. Unlike complete proteins, which contain all nine essential amino acids and are generally found in animal products, incomplete proteins are usually found in foods like legumes, grains, nuts, and seeds.

Plant sources can benefit a diet by providing fiber, vitamins, and minerals, but they typically require careful meal planning to ensure that one gets a complete range of essential amino acids. This can often be achieved by combining different plant proteins in a meal, such as pairing rice with beans.

Complete proteins, on the other hand, are primarily associated with animal sources, while whole protein is not a standard classification in nutritional contexts. Hence, the designation of incomplete protein accurately aligns with plant-derived protein sources.