What are essential amino acids?

Essential amino acids are specific amino acids that the human body cannot synthesize on its own and therefore must be obtained through the diet. There are nine essential amino acids that are crucial for various bodily functions, including protein synthesis, tissue repair, and the production of enzymes and hormones. Since the body lacks the mechanisms to produce these amino acids, a sufficient intake through foods such as meat, dairy, eggs, and certain plant sources like quinoa and soy is vital for maintaining health and proper physiological functions.

The other options refer to different aspects of amino acids; some can be produced by the body, some are significant for muscle growth, and others are involved in energy levels, but this does not define what makes an amino acid "essential." In summary, essential amino acids must come from dietary sources, which is why this choice is the correct one.