Bioacessibilidade e Biodisponibilidade da fenilalanina após a digestão in vitro

Abstract

Phenylketonuria is an autosomal recessive disorder that affects phenylalanine metabolism, preventing the conversion of this amino acid into tyrosine and increasing its blood levels to toxic concentrations. Treatment for this disorder begins immediately after diagnosis, which is carried out through neonatal screening and consists of a protein-restricted diet supplemented with a free amino acid formula. The accumulation of phenylalanine in the bloodstream, in untreated cases, can cause severe intellectual disability, behavioral problems, cognitive impairments, and other dysfunctions. Given that the consumption of intact dietary proteins offers superior nutritional benefits compared to the intake of free amino acids, assessing the bioavailability of phenylalanine in various food sources—and how different preparation methods may affect it—is essential for the development of optimized dietary therapies. Such insights can support more individualized and potentially less restrictive treatment approaches. This study investigated the bioaccessibility and bioavailability of phenylalanine across different food matrices, with particular attention to the effects of food processing. The primary objective was to determine the extent to which this amino acid becomes bioavailable for absorption following digestion. Bioaccessibility refers to the fraction of a nutrient that is released from the food matrix during digestion and is available for absorption and metabolism. In contrast, bioavailability denotes the portion of the digested nutrient that is actually absorbed and utilized by the body. Food samples—including cooked white rice, cooked brown rice, boiled potatoes, and baked pre-fried potatoes—were selected based on a survey administered to patients with phenylketonuria, their parents or caregivers, and healthcare professionals working in the field. The samples underwent simulated gastrointestinal digestion using the INFOGEST 2.0 protocol and were applied to Caco-2 cells to assess their bioavailability. The results showed that bioaccessibility varied depending on the food matrix and processing method. Cooked potato had the highest bioaccessibility (48.45%), followed by brown rice (37.09%), white rice (26.80%), and baked pre-fried potato (22.75%). In terms of bioavailability—i.e., the amount of phenylalanine absorbed through the cell monolayer—there was significant variation, with brown rice showing the lowest bioavailability (1.43%), followed by cooked potato (2.39%), white rice (6.83%), and baked pre-fried potato, which showed a significant difference from the other samples (95.5%), suggesting that intense thermal processing may enhance the absorption of this amino acid. The Caco-2 cell tests indicated that the monolayer remained intact, ensuring reliable results. The higher bioavailability of baked pre-fried potato may be related to moisture reduction and protein concentration during processing. On the other hand, brown rice, which contains a high amount of dietary fiber (2.12%), showed lower bioavailability, possibly due to the difficulty in digesting and absorbing phenylalanine in the presence of fiber. Therefore, it was concluded that the bioaccessibility and bioavailability of phenylalanine do not depend solely on its total composition in the food but also on the food matrix composition and the type of processing applied. Preparation methods can influence phenylalanine absorption, potentially impacting dietary recommendations regarding the quantity of food that can be consumed.