Phenylalanine is an essential amino acid, meaning that the body cannot produce it and must obtain it from food. It plays a crucial role in the production of proteins and the synthesis of important neurotransmitters, such as dopamine, which are vital for brain function and mood regulation. Foods rich in phenylalanine include meat, fish, eggs, dairy products, nuts, and soy products. In some individuals, particularly those with a genetic disorder called phenylketonuria (PKU), the body cannot properly metabolize phenylalanine. This can lead to harmful levels in the blood, potentially causing serious health issues, including intellectual disabilities. Therefore, people with PKU must follow a strict diet low in phenylalanine to manage their condition.