Vitamin D and Health Outcomes in Preterm Born Population

Goals: * To investigate the impact of VitD and mineral supplementation and biochemistry in infancy on health outcomes at the age of 5 years in childhood (bones, teeth, muscles, heart, lungs) after preterm birth (Preterm Child group) * To investigate the impact of VitD and mineral supplementation and biochemistry in infancy on health outcomes at the age of 24-25 years in adulthood (bones, teeth, muscles, heart, lungs) after preterm birth (Preterm Adult group) Subjects: * Preterm Child group; Children, who were born prematurely before before 32 gestation weeks and before 34 gestation weeks with very low birth weight (VLBW, \< 1500g) in Oulu University Hospital and/or cared in Neonatal Unit with VitD concentration measured before discharge during the years 2014 to 2017. * Preterm Adult group; Adults, who were born prematurely before 32 gestation weeks and before 34 gestation weeks with very low birth weight (VLBW, \< 1500g) in Oulu University Hospital and/or cared in Neonatal Intensive Unit during the years 1994 to 1997. For power calculation, the amount of participants for the adult group was done by estimating the inadequately low vitamin D concentration (\< 50 nmol/l) to be found in 28 % of preterm born adults. (In Northern Finnish birth cohort 28 % at the age of 31 had serum 25-OH vitamin D concentration \< 50 nmol/l in 1997). With the estimation of supplementation to decrease the percentage of participants with low vitamin D to 9 %, the required amount of participants would be minimum of 56 per group. Furthermore, if the level after supplementation is estimated to be low only in 2,8 %, the amount would be required as 29 cases per group. Methods in protocol: At the first visit and in the end of intervention; measurements of length, weight, head circumference, waist-to-hip ratio will be done; muscular power is assessed by grip test of both hands; lung function test with bronchodilatation is done at the first appointment; heart ultrasound, blood pressure measurement and bicycle stress test with a circadian electrocardiography will be done in the beginning and at the end; bone mineralisation will be measured by dual energy x-ray absorptiometry (DXA) and ultrasound methods; VitD concentration will be measured 4 months interval during the follow up. The control peers participate only the first visit. The child group will be assessed only once and without bicycle stress test.