VITAMIN-B-6 STATUS OF SCHOOL-AGED PATIENTS WITH PHENYLKETONURIA

A triad of measures of vitamin B-6 (B6) status (diet, plasma, and urin e) was evaluated in 15 patients with phenylketonuria (PKU) and six con trol subjects (6-17 y). I) 4-d reported dietary intakes of protein and B6; 2) fasting plasma concentrations of pyridoxal 5'-phosphate (PLP), total B6 (TB6), and alkaline phosphatase (AP) activity; and 3) 24-h u rinary excretions of TB6 and 4-pyridoxic acid (4-PA). Compared with co ntrol subjects, patients had a significantly reduced mean protein inta ke (P < 0.001) and increased mean B6 intake (P < 0.05). Mean dietary B 6:protein in patients, 0.043 mg/g protein, was over twice that of cont rol subjects, 0.018 mg/g protein (P < 0.001). Mean plasma PLP and PLP/ TB6 in patients were significantly increased compared with control sub jects (P less than or equal to 0.05). As a percent of B6 intake, mean urine TB6 was similar between the groups (6.8% patients vs 6.5%, contr ol subjects). These findings, along with a lower mean plasma AP activi ty in patients, support the possibility of a reduced turnover of the v itamin in PKU.