Incomplete proteins are proteins that do not contain all nine essential amino acids required by the human body. These amino acids are termed "essential" because the body cannot produce them on its own and must obtain them from food sources. Incomplete proteins are typically found in plant-based foods such as grains, nuts, seeds, and legumes. To meet protein needs, individuals consuming incomplete proteins can combine different food sources. For example, pairing rice with beans creates a complete protein profile, as the amino acids in one complement those in the other. This practice is especially important for vegetarians and vegans to ensure adequate protein intake.