How many essential amino acids are required by the body?

The correct answer indicates that the human body requires nine essential amino acids. These amino acids are termed "essential" because they cannot be synthesized by the body and must be obtained through dietary sources. The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Each of these plays a critical role in various physiological functions, including protein synthesis, tissue repair, and the production of hormones and enzymes.

While there are amino acids that the body can produce (non-essential amino acids), the essential ones are pivotal for maintaining health and optimal functioning. Knowledge of the specific number of essential amino acids is important for understanding protein sources and dietary needs, particularly for those following various dietary regimens such as vegetarianism or veganism, where protein intake must be carefully managed to include all the essential amino acids.