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Prof Care Mother Child. 1998;8(4):109-10.
The phenylalanine-free diet is needed for the treatment of phenylketonuria. Phenylketonuria is an inherited metabolic condition in which there is a deficiency of the enzyme phenylalanine hydroxylase. Lack of this enzyme means the body cannot metabolise the essential amino acid phenylalanine, which then builds up in the blood and causes mental retardation and other abnormalities. Retardation can be prevented if phenylketonuria is diagnosed in the first three weeks of infancy and dietary treatment started straightaway. There is a universal screening test in the UK (the Guthrie test). Heel-prick blood samples are taken from all babies between 6-14 days old and analysed at a regional screening centre. For infants, a phenylalanine-free formula is needed, either as a supplement before breast feeds or following a formula feed. The diet must continue during weaning and childhood, with a low protein diet. Foods such as meat, fish, eggs, milk, cheese, nuts and pulses are excluded as they contain high levels of phenylalanine. Vegetables and fruit are allowed in measured amounts only! Special low protein bread, pasta, biscuits and flour are used to supplement the diet and ensure adequate calorie intake. Whether the diet can be stopped at the end of adolescence is debatable. If stopped, it should be re-started at conception and maintained during pregnancy, as high levels of phenylalanine in the mother can affect the fetus.
苯丙酮尿症的治疗需要无苯丙氨酸饮食。苯丙酮尿症是一种遗传性代谢疾病，体内缺乏苯丙氨酸羟化酶。缺乏这种酶意味着身体无法代谢必需氨基酸苯丙氨酸，苯丙氨酸随后在血液中积聚，导致智力发育迟缓及其他异常。如果在婴儿期的前三周诊断出苯丙酮尿症并立即开始饮食治疗，智力发育迟缓是可以预防的。在英国有一项通用的筛查测试（古思里测试）。从所有6至14天大的婴儿足跟采集血样，并在地区筛查中心进行分析。对于婴儿，需要无苯丙氨酸配方奶粉，可在母乳喂养前作为补充，或在配方奶喂养后使用。在断奶和儿童期必须持续这种饮食，采用低蛋白饮食。肉类、鱼类、蛋类、牛奶、奶酪、坚果和豆类等食物被排除在外，因为它们含有高水平的苯丙氨酸。蔬菜和水果只能限量食用！使用特殊的低蛋白面包、意大利面、饼干和面粉来补充饮食并确保足够的热量摄入。饮食在青春期结束时是否可以停止存在争议。如果停止，应该在受孕时重新开始并在孕期持续，因为母亲体内高水平的苯丙氨酸会影响胎儿。
