No abstract

To determine whether the n-6 and n-3 polyunsaturated fatty acid levels can be affected by the PKU diet, fatty acid composition was studied in PKU subjects and controls together with their lipid intake. The study population consisted of 40 PKU patients treated with a phenylalanine-restricted diet. Controls were 50 children on whom preoperative tests had been carried out for minor surgery. Methyl esters were obtained from plasma and red blood-cells and separated by gas chromatography. PKU patients showed lower docosahexaenoic acid levels (22: 6 n-3) (p < 0.001) and higher n-6 series levels in plasma (18:2 n-6) (p < 0.001) and in red blood-cells (20: 4 n-6) (p < 0.001) than the control population. Since docosahexaenoic and arachidonic acids are fundamental structural components for normal brain development, it seems necessary to consider a dietary adjustment in these patients.

There was a significant decrease in the proportion of omega 3 PUFA in plasma from the first to the third trimester. Thus, it is suggested that the omega 3 PUFA intake during pregnancy should be increased in the last trimester.

From a biochemical point of view, and taking into account the pre-existing literature, it is suggested that a minimum fatty fish intake of twice per month should be recommended (edible portion 85 g.) in order to reach the N-6/N-3 quotient usually proposed.