Body mass index in adult patients with diet-treated phenylketonuria.

BACKGROUND: There is an increasing number of adults with phenylketonuria (PKU) on a low phenylalanine diet. In the general population, an increasing body mass index (BMI) in the UK is a major problem with associated co-morbidities. The present study aimed to identify whether patients with diet-treated PKU have obesity rates comparable to those in the general population. METHODS: Two hundred and thirty-six PKU subjects (49% male, 51% female), aged >16 years, who were diagnosed by newborn screening and were receiving a low phenylalanine diet, were identified from seven metabolic centres in the UK. Retrospective data were collated on age, sex, BMI and mean phenylalanine concentration over the previous 12 months. RESULTS: Mean (SD) phenylalanine concentration for all 236 subjects was 789 (311) µm; mean (SD) BMI was 26 (5.4) kg m(-2) [males 25 (4.3) kg m(-2) , females 27 (6.2) kg m(-2) ]; mean (SD) age was 26 (7) years; and 55% had a BMI > 25 kg m(-2) . The percentage of subjects with a BMI >25 kg m(-2) and >30 kg m(-2) , as well as increasing obesity with age, was similar to the UK population. A correlation was observed between increasing BMI and a higher phenylalanine concentration (r = 0.243, P = 0.001). CONCLUSIONS: The number of overweight and obese patients with diet-treated PKU in the UK is a concern. This could lead to other obesity-related complications increasing the complexity of diet and the cost of their care. There is a need to educate patients with respect to adopting a healthy, low phenylalanine diet and lifestyle to prevent further rises in BMI.

Adults with late diagnosed PKU and severe challenging behaviour: a randomised placebo-controlled trial of a phenylalanine-restricted diet.

BACKGROUND: Although early diagnosis and treatment in phenylketonuria (PKU) leads to excellent outcomes, a population of adults born before the introduction of newborn screening exists. They can have severe intellectual disabilities and behavioural problems, and are often dependent on full-time carers. Anecdotal evidence suggests that a diet that lowers blood phenylalanine concentration can have significant benefits upon behaviour. METHODS: A prospective double-blind randomised placebo-controlled crossover trial of phenylalanine-restricted diet was performed in a group of 34 adults (aged 21-61 years, median 49) with late diagnosed PKU with severe challenging behaviour. RESULTS: Only 17 completed the 60 week study: seven withdrew before the end of the baseline period; five withdrew during the first diet period; five withdrew during the second diet period (after moving into placebo phase). The mean (SD) blood phenylalanine was 1570 (222) micromol/l during baseline, 553(158) mumol/l during the active phase and 1444 (255) micromol/l during the placebo phase. In the 22 participants exposed to both active and placebo phases, no differences were demonstrated in behaviour assessed by the Aberrant Behavior Checklist and Vineland Adaptive Behavior Scales, behaviour diaries or on video analysis of direct observations. However, 76% of carers' comments were scored as positive during the active phase, compared with 54% during the placebo phase (chi(2) = 38.06, p<0.001). CONCLUSIONS: There are significant challenges in studying people with intellectual disabilities and considerable difficulties in instituting phenylalanine-restricted diet in this population. However, if attempted, there are potential benefits to quality of life for the individuals with PKU and their carers.

The determination of phenylalanine content of foods suitable for phenylketonuria.

BACKGROUND: A low phenylalanine diet for people with phenylketonuria (PKU) is very restrictive. Natural foods allowed are based chiefly on fruits and vegetables but there is limited analysis on the phenylalanine content of newer and exotic fruit and vegetables. The assumption that 1 g protein yields 50 mg phenylalanine does not apply to fruits and vegetables. METHODS: The National Society for Phenylketonuria Medical Advisory Panel commissioned the phenylalanine analysis of 172 foods, which emphasis on fruit and vegetables. The foods were purchased from retail outlets and analysed by LGC Limited (67 foods) and the LFI (105 foods). RESULTS: There was a strong correlation between this phenylalanine and UK analyses published in 1980, but previous analysis included only a limited range of fruits and vegetables (r = 0.8746; P < 0.0001). There was also correlation between phenylalanine and UK protein analyses (r = 0.7976; P < 0.0001). CONCLUSION: This new phenylalanine data have enabled a wider range of fruits and vegetables to be safely incorporated into the diet of people with PKU.