Omega-3 Long-Chain Polyunsaturated Fatty Acids and Phenylketonuria
The brain, retina and other nervous tissues are rich in long chain polyunsaturated fatty acids (LCPUFA). Many clinical and epidemiological studies have proven omega-3 LCPUFA to produce positive effects on neural development in childhood. Long-chain PUFA can be synthesised endogenously from the parent essential fatty acids when dietary intakes are adequate. Protein-rich foods such as meat, fish, eggs, liver and milk products are also the predominant dietary sources of LCPUFA, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, patients with classical phenylketonuria (PKU) require strict lifelong limitation of dietary protein intake to avoid high plasma concentrations of phenylalanine and neurological damage. This type of strict metabolic control usually provides not only lower amounts of vitamins and minerals but also lower amounts of saturated fatty acids and PUFA. Therefore, PKU patients have very low LCPUFA intakes and reduced LCPUFA concentrations in plasma and erythrocytes as compared to healthy controls. During infancy and childhood, LCPUFA are important for normal neurodevelopment. A deficiency may contribute to disturbances in the function of the central nervous system, which are detectable as early as in preschool and school-age children with PKU. Moreover, it has been suggested that the LCPUFA deficiency may lead to chronic neurological, inflammatory and metabolic disorders. On the other hand, data from randomized controlled trials suggest that LCPUFA status in patients with PKU may be improved by dietary supplementation. In this review, the association between phenylalanine restricted diets and LCPUFA was investigated and the importance of LCPUFA for patients with PKU was discussed.