How are essential amino acids defined?

Essential amino acids are defined as those that must be obtained through diet because the human body lacks the capability to synthesize them. There are nine essential amino acids that play a vital role in various physiological functions, such as building proteins, supporting metabolic processes, and maintaining overall health. Since the body cannot create these amino acids internally, it is crucial to include protein-rich foods in the diet, such as meat, dairy, eggs, and certain plant-based sources like quinoa and soy, to ensure adequate intake. This distinction between essential and non-essential amino acids is foundational in nutrition, emphasizing the importance of dietary sources for optimal health.