Micronutrients, Essential Fatty Acids and Bone Health in Phenylketonuria

Abstract

Introduction: In phenylketonuria (PKU), a natural protein-restricted dietary treatment prevents severe cognitive impairment. Nutrient deficiencies may occur due to strict diet. This study is aimed at evaluating the dietary intake and blood concentrations of micronutrients and essential fatty acids (FA), bone mineral density (BMD) and fracture history in patients on long-term dietary treatment. Methods: Sixty early diagnosed Dutch patients (aged 1-39 years) were included in a multi-center cross-sectional study. Their dietary intake, blood concentrations of micronutrients, FA, fracture history and BMD were assessed. Results: Selenium dietary intake and serum concentrations were low in 14 and 46% of patients, respectively. The serum 25-OH vitamin D2 + D3 concentration was low in 14% of patients while 20% of patients had a low vitamin D intake. Zinc serum concentrations were below normal in 14% of patients, despite adequate intake. Folic acid serum concentrations and intake were elevated. Despite safe total protein and fat intake, arginine plasma concentrations and erythrocyte eicosapentaenoic acid were below reference values in 19 and 6% of patients, respectively. Low BMD (Z-score <-2) was slightly more prevalent in patients, but the lifetime fracture prevalence was comparable to the general population. Conclusions: Dutch patients with PKU on long-term dietary treatment have a near normal nutrient status. Supplementation of micronutrients of which deficiency may be deleterious (e.g., vitamin D and selenium) should be considered. BMD warrants further investigation.

Response to the Letter to the Editor Regarding “Micronutrients, Essential Fatty Acids and Bone Health in Phenylketonuria”

“…Importantly, this is comparable to the percentage reported by us [1], even though they describe a population with mainly adult patients.…”

“…Approximately 4.9-7.4% of early treated patients with PKU may have a BMD Z-score below -2 SD, as opposed to 2.5% in the general population. This means that approximately 95% of early treated Dutch patients with PKU are not at risk for low BMD, and this is a much better outcome than expected from reports in the literature [1,6].…”

“…We would like to respond to the letter of our colleagues Hansen, Binkley and Ney about our research published in your journal [1]: a study about micronutrient status, bone mass and fracture rate in a population of patients with phenylketonuria (PKU; n = 60). They present several concerns about our conclusions and we would like to address their remarks.…”

High Fracture Rates in Young Patients with Phenylketonuria

“…Demirdas et al [1] have reported that 42% of 60 phenylketonuria (PKU) patients (median age 13 years, 58% female) sustained ≥1 fracture and have described bone mineral density (BMD) in a subset. These authors have concluded that "low BMD (Zscore <-2) was slightly more prevalent in patients" and "the lifetime fracture prevalence of patients seems comparable to the general population (41.7 vs.…”

“…Unfortunately, several points need clarification. We hereby recommend that Demidras et al [1] reanalyze their data in the following manner:…”