Lamberts® phenylalanine is the natural l-phenylalanine and is presented in its free-form to help ensure optimal absorption. This product is made in the uk to pharmaceutical gmp standards. Please note: people with a condition known as phenylketonuria (pku) in which phenylalanine cannot be broken down should not take phenylalanine supplements. Nor should phenylalanine supplements be taken in conjunction with prescription anti-depressants particularly monoamine oxidase (mao) inhibitors. Daily intake: 1 capsule lamberts quantity – 60 capsules l-phenylalanine 500mg.