Long-term compliance with a novel vitamin and mineral supplement in older people with PKU

Background: The long-term efficacy of vitamin and mineral preparations in dietary-treated adult patients with phenylketonuria (PKU) is unreported. Aim: In an open, intervention trial, the acceptability, safety and impact on biochemical and haematological micronutrient status of a new vitamin and mineral tablet (Phlexy Vits, SHS International) was investigated. Methods: Fifteen subjects with PKU (median age 21 years, range 8-33 years) on low-phenylalanine diet from two PKU centres were recruited. No vitamins or minerals were added to their protein substitute and for 12 months they took their full daily requirements of vitamin and minerals from Phlexy Vits (5 tablets daily). All but two subjects had taken alternative vitamin and mineral supplements before the trial. Fasting bloods were taken at baseline (week -2 and at week 0), 4 and 12 months for a range of biochemical and nutritional measurements. Results: By 4 months, serum vitamin B₁₂ (p=0.003), serum manganese (p=0.03) and plasma (p=0.03) and red blood cell (p=0.004) glutathionine peroxidase (GSHPx) all significantly increased but remained within normal reference ranges. By 12 months, serum vitamin B₁₂ (p < 0.05) and plasma GSHPx (p < 0.05) remained increased. The Phlexy Vits tablets scored better than conventional vitamin and mineral supplements for overall acceptability (p < 0.05), and ease of swallowing (p = 0.1) at 4 months, although swallowing score deteriorated by 12 months (p < 0.05). There was a small but significant deterioration in compliance with taking the vitamin and mineral supplements between 4 and 12 months (p < 0.05). Conclusion: In the long term, these comprehensive vitamin and mineral tablets appeared acceptable and improved biochemical nutritional status, although there were long-term compliance and swallowing issues.