# Risk of inadequate protein and micronutrient intakes in patients with PKU with an increased phe-tolerance: Impact of a micronutrient-dense protein substitute

## TL;DR

People with PKU who can tolerate more phenylalanine may still have poor nutrition, but a special protein substitute can help improve their nutrient intake.

## Contribution

A micronutrient-dense protein substitute improved nutrient intakes in PKU patients with increased phenylalanine tolerance.

## Key findings

- Baseline protein and essential amino acid intakes were below recommendations for some patients.
- Micronutrient intakes improved significantly after the intervention, except for vitamin B12 and phosphorus.
- Blood phenylalanine levels remained stable, and DHA intake increased.

## Abstract

Patients with phenylketonuria (PKU) with higher phenylalanine (phe)-tolerance may have inadequate diets due to high-quality protein restriction and reduced intakes of nutrient-fortified phe-free, tyrosine (tyr)-enriched protein substitutes (PS).

Open-label, 24-week, multi-centre intervention assessed the impact of a once-daily, micronutrient-dense PS on nutrient intakes in patients with an increased phe-tolerance. Subjects >12 years, consuming 0–25 g protein/day from a regular PS, were recruited. Diet records and fasting blood samples were collected at baseline and study end.

11/13 subjects, 15-49y (5 males), with 6/11 taking tetrahydrobiopterin dihydrochloride (BH4) and/or a regular PS, completed the study. At baseline, protein and some essential amino acids (EAA) intakes were below recommendations in 4/11 and 3/11 subjects, respectively. Vitamins A, B2, B12, D, calcium, iron, iodine, zinc and magnesium intakes were below recommendations for 7/11. After the intervention, 2/11 had total protein intakes below recommendations, while 11/11 met EAA recommendations. Micronutrient intakes improved to ≥90 % of recommendations for all subjects except for vitamin B12 (4/11) and phosphorus (1/6). Docosahexaenoic acid (DHA) intakes increased. Blood phe levels remained stable.

Patients with PKU who have relaxed their phe-restricted diet are at risk of insufficient nutrient supply, and dietary counselling should be offered. Consuming the study PS increased nutrient intakes closer to dietary recommendations.

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•Patients with PKU on a relaxed phe-restricted diet are at risk of insufficient nutrient supply•The study protein substitute increased nutrient intakes closer to dietary needs.•Patients blood Phe levels remained stable, and DHA intake improved.

Patients with PKU on a relaxed phe-restricted diet are at risk of insufficient nutrient supply

The study protein substitute increased nutrient intakes closer to dietary needs.

Patients blood Phe levels remained stable, and DHA intake improved.