Medical Nutrition Therapy and Intestinal Microbiota in Phenylketonuria

The healthy intestinal microbiota has crucial effects, such as protection from pathogenic factors and the development of the immune system. The composition, diversity, and functioning of the microorganisms that make up the microbiota, change at short notice with dietary factors. In this respect, medical nutritional therapies applied in congenital metabolic diseases play a crucial role in shaping the intestinal microbiota. These dietary interventions, with their unique macronutrient and micronutrient compositions, interact with the microbiota, modulate immune responses, and alter the protective integrity of the gut epithelial barrier. In phenylketonuria, the most common amino acid metabolism disorder, it is thought that there may be differences in the microbiota due to the phenylalanine-restricted diet therapy that must be applied throughout life, and studies have been carried out on this subject. Studies have concluded that differences in microbial diversity exist in phenylketonuria patients, although it is not yet known whether it is a result of the disease itself or dietary therapy. This review is intended to examine the medical nutritional therapy administered in phenylketonuria and its effects on the intestinal microbiota.