Which type of amino acids cannot be synthesized by the human body?

The correct answer is essential amino acids. These amino acids are termed "essential" because the human body cannot synthesize them; therefore, they must be obtained through dietary sources. There are nine essential amino acids that the body requires for various functions, including building proteins, repairing tissues, and supporting metabolic processes.

In contrast, nonessential amino acids can be synthesized by the human body, meaning that they do not need to be obtained from food. Conditional amino acids are generally categorized as nonessential, as the body can produce them, but under specific conditions (such as illness or stress), the body may require them from dietary sources. Trace amino acids is not a recognized category in the context of amino acids and their synthesis.

Understanding the distinction between essential and nonessential amino acids is crucial for nutritional science and diet planning, as it emphasizes the importance of incorporating a variety of protein sources to ensure adequate intake of all essential amino acids for optimal health.