Abstract
This is the first study to evaluate vitamin K status in relation to dietary intake and phenylalanine dietary compliance in patients with phenylketonuria (PKU). The dietary and PKU formula intake of vitamin K was calculated in 34 PKU patients, with vitamin K status determined by the measurement of prothrombin induced by vitamin K absence (PIVKA-II). Blood phenylalanine concentrations in the preceding 12 months were considered. There were significantly more phenylalanine results exceeding 6 mg/dL in patients with normal PIVKA-II concentrations than in those with abnormal PIVKA-II levels (p = 0.035). Similarly, a higher total intake of vitamin K and dietary vitamin intake expressed as μg/day (p = 0.033 for both) and %RDA (p = 0.0002 and p = 0.003, respectively) was observed in patients with normal PIVKA-II levels. Abnormal PIVKA-II concentrations were associated with a lower OR (0.1607; 95%CI: 0.0273–0.9445, p = 0.043) of having a median phenylalanine concentration higher than 6 mg/dL. In conclusion, vitamin K deficiency is not uncommon in phenylketonuria and may also occur in patients with adequate vitamin K intake. PKU patients with better dietary compliance have a higher risk of vitamin K deficiency. The present findings highlight the need for further studies to re-evaluate dietary recommendations regarding vitamin K intake, both concerning formula-based and dietary consumption of natural products.
Highlights
The standard treatment in classical phenylketonuria (PKU) is based on the elimination of high-protein food, food for special medical purposes (FSMP)containing no phenylalanine (Phe) and special low-protein food items are essential for therapy
Despite all efforts undertaken to adapt medicinal products to the needs of PKU patients, and high micronutrient intake, biochemical markers suggest that some deficiencies still occur [3,4], highlighting the further need for the nutritional profiling of L-amino acid supplements in PKU
A higher total intake of vitamin K and dietary vitamin intake expressed as μg/day (p = 0.033 for both) and %recommended daily allowance (RDA) (p = 0.0002 and p = 0.003, respectively) was observed (Table 2) in patients with normal PIVKA-II levels
Summary
The standard treatment in classical phenylketonuria (PKU) is based on the elimination of high-protein food (meat, milk, bread, etc.), food for special medical purposes (FSMP)containing no phenylalanine (Phe) and special low-protein food items (e.g., bread-lp, cheese-lp, milk-lp) are essential for therapy. The standard treatment in classical phenylketonuria (PKU) is based on the elimination of high-protein food (meat, milk, bread, etc.), food for special medical purposes (FSMP). Nutrients 2020, 12, 1772 introduction of Phe-free preparations into PKU therapy, their composition has continuously been modified and improved. Within the last few years, PKU FSMPs were supplemented with selenium and docosahexaenoic acid. Despite all efforts undertaken to adapt medicinal products to the needs of PKU patients, and high micronutrient intake (median above 200% of the reference nutrient intakes-RNI), biochemical markers suggest that some deficiencies still occur (e.g., selenium, zinc) [3,4], highlighting the further need for the nutritional profiling of L-amino acid supplements in PKU. Over the last few decades, the perception of the role of vitamin K has changed significantly. Schwalfenberg appreciated the emerging group of vitamins (K1 and K2)
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