Neonatal hypertyrosinemia and evidence for deficiency of ascorbic acid in Arctic and subarctic peoples.

Hypertyrosinemia tyrosine concentration in whole blood greater than 0.42 mmol/l or 7.5 mg/dl is prevalent among lnuit newborn of the Canadian Eastern Arctic. The rate was 14.8 per 100 newborn between January 1970 and December 1972 (first survey period) and 6.2/100 between January 1973 and September 1974 (second survey period); the corresponding rates among Indian newborn of Nouveau Quebec were 2.6 and 2.2%. Among Anglo-Saxons the rate was less than 0.5% and in French Canada it commonly exceeded 0.94%. Serum concentrations of ascorbic acid were low (less than or equal to 0.25 mg/dl) in the pregnant and age-matched adult lnuit when measured by Nutrition Canada during the first survey period. The percentages of inuit children (up to 4 years old) and pregnant women at "high risk" for scurvy (serum concentration of ascorbic acid less than 0.2 mg/dl) were 14.8 and 47.1, respectively; the corresponding national percentages were 3.0 and 2.2, respectively. Deficiency of ascorbic acid in pregnant women is probably the cause of the unusual prevalence of neonatal hypertyrosinemia among the native Arctic and subarctic peoples because ascorbic acid is required to maintain optimal activity of p-hydroxyphenylpyruvic acid hydroxylase and to permit normal oxidation of tyrosine.