Effects of Inadequate Amino Acid Mixture Intake on Nutrient Supply of Adult Patients with Phenylketonuria

Abstract

Background: Adult phenylketonuria (PKU) patients often reduce their intake of amino acid mixture (AAM) to less than the prescribed amounts. Effects of reduced AAM intake on nutrient supply were evaluated. Methods: Nutrient intake was calculated in 20 adult PKU patients based on a structured food record and complemented by laboratory assessment of nutritional status. Patients were classified into 2 groups, (A) regular AAM intake, or (B) AAM intake below calculated requirements. Results: Group B consumed a higher proportion of natural protein (60 ± 23 vs. 33 ± 12%, p = 0.002); however, the total protein intake was below the recommended amounts in 60% of patients in group B versus 7% in group A (p = 0.03). Fat intake was higher in group B (39 ± 9% of energy vs. 31 ± 6%, p = 0.03), mainly from saturated fats. Selenium, folate, and vitamin B12 intake was below the recommended intake in group B. However, serum concentrations of these analytes remained within the normal range in both groups, although vitamin B12 levels were lower in group B. Plasma tyrosine correlated with AAM intake, and hydroxyproline correlated with the amount of natural protein consumed. Conclusion: Relaxed AAM intake resulted in insufficient nutrient supply, despite a compensatory increase in consumption of natural protein. Care needs to be taken to ensure adequate nutrition in adults with PKU.

Improved Eating Behaviour and Nutrient Intake in Noncompliant Patients with Phenylketonuria after Reintroducing a Protein Substitute: Observations from a Multicentre Study

“…This represents an important outcome as the intake of calcium, magnesium, iron, zinc, iodine, vitamin D at baseline were below the UK RNI recommendations [23]. Evidence of blood- and diet-reported micronutrient insufficiencies supports previous studies in adult PKU patients following a relaxed diet together with relaxed and/or discontinued protein substitute intakes [15,16]. This study also provides evidence that an inadequate intake of these nutrients is evident in patients following an unrestricted diet which has not previously been described, despite reporting higher intakes of natural protein.…”

“…More recently, 43% of adult patients in the UK admitted to not following the PKU diet [13]. Noncompliant patients are therefore typically not under strict dietary control, have a variable degree of natural protein restriction and tend to relax and/or completely discontinue taking protein substitutes [14,15].…”

“…Coupled with increased concentrations of circulating phenylalanine and thus poorer metabolic control, noncompliance may make patients at risk of nutritional deficiencies compared to fully compliant counterparts and healthy controls. Patients relaxing and/or stopping the PKU diet display insufficient nutrient intakes, despite compensatory increases in natural protein intake [15,16]. Insufficient intakes have been reported for vitamin B 12 , iron, zinc, vitamin D 3 , calcium, selenium, iodine [15,16] and long-chain polyunsaturated fatty acids (particularly DHA and arachidonic acid) [17,18].…”

“…Patients relaxing and/or stopping the PKU diet display insufficient nutrient intakes, despite compensatory increases in natural protein intake [15,16]. Insufficient intakes have been reported for vitamin B 12 , iron, zinc, vitamin D 3 , calcium, selenium, iodine [15,16] and long-chain polyunsaturated fatty acids (particularly DHA and arachidonic acid) [17,18]. Impairments in executive functioning, information processing (reaction times, attention) and mood (increased inhibition, anxiety, depression and low self-esteem) have also been reported in noncompliant PKU patients and likely transpire due to the pathophysiological consequences of disrupted phenylalanine hydroxylation [19,20].…”

Vitamin K Status in Adherent and Non-Adherent Patients with Phenylketonuria: A Cross-Sectional Study

“…There have been reports on adequate or inadequate vitamin K intake in PKU patients on a diet [ 13 , 14 , 15 ]. Still, even in recent studies investigating possible vitamin and micronutrient deficits, the status of vitamin K is not addressed [ 16 , 17 , 18 ]. Our present report is, to the best of our knowledge, one of the very few studies to investigate the status of vitamin K in PKU patients and the first to evaluate vitamin K status in relation to dietary intake and Phe dietary compliance.…”