Introduction: It was tested if a healthy school meal would result in significant changes in selected blood parameters and if such parameters would lie within generally accepted optimal values.
Material and methods: The study was a block-randomized, controlled trial in which 145 pupils delivered blood before (week 39) and after the intervention (week 49). The intervention group received a healthy meal for two months (25-30% of the daily intake of calories). Blood samples were analyzed for 17 parameters related to carbohydrate, fat and protein metabolism as well as vitamins and minerals.
Results: During the intervention period, the intervention group showed a significant change in mean values for thyroid-stimulating hormone (TSH), calcium (CA) haemoglobin (HB), cobalamin (COBA) and creatinine (CREA) compared with the control group (p < 0.025). The optimal value for vitamin D in serum is about 80 nmol/l. In week 49, more than 94% of the pupils were lower than 80 nmol/l, and they generally had low calcium values.
Conclusion: The intervention group showed significant alterations in TSH, CA, HB, COBA and CREA values from the start to the end of the intervention period compared with the control group. The results should be confirmed in a study with more participants over a longer period of time. The teenagers in the study did not have sufficient vitamin D. Treating adolescents with a daily dose of vitamin D should be considered .