Aim: To establish the frequency and causes of vitamin D insufficiency in healthy female adolescents in Izmir, Turkey. Methods: 64 adolescents from a low- (Ikinci Inönü) and a high- (Ilica) socio-economic settlement were included. Parents’ monthly income was classified as low, middle and high. The blood samples were drawn at the end of the summer and winter periods. Results: Vitamin D insufficiency percentages for the end-of-winter period were 59.4% in Ikinci Inönü and 15.6% in Ilica, and for the end of summer 25% and 15.6%, respectively. Calcidiol levels of cases from Ikinci Inönü were found to be lower compared with the levels of cases from Ilica (34±15 vs 59±24 nmol/l for end of winter, p= 0.000; 51±22 vs 65±28 nmol/l for end of summer, p= 0.03). Calcidiol levels of cases whose parental monthly income was low and whose mothers were illiterate were significantly lower than the others (48±18 vs 65±29 nmol/l for end of summer, p= 0.01; 33±16 vs 56±23 nmol/l for end of winter, p= 0.000; 45±13 vs 64±29 nmol/l for end of summer, p= 0.007; 36±17 vs 51±25 nmol/l for end of winter, p= 0.02; respectively).
Conclusion: Vitamin D insufficiency was frequent, especially in the end-of-winter period. Basic risk factors were low socio-economic status, illiteracy of mothers and low calcium intake.