People who do not produce phenylalanine hydroxylase would have a condition called phenylketonuria (PKU). PKU is a genetic disorder that prevents the body from breaking down the amino acid phenylalanine, which is found in many foods, including meat, dairy products, nuts, and beans. If phenylalanine is not broken down, it can build up in the blood and cause serious health problems, including intellectual disability, seizures, and behavioral problems.

PKU is treated by following a special diet that is low in phenylalanine. This diet can help prevent the buildup of phenylalanine in the blood and reduce the risk of serious health problems.