The increased amount of vitamin B12 in serum is needed to minimize the uracil misincorporation into DNA during folate supplementation

The aim of the study was to find out the effect of dietary intake of folate and folic acid supplementation on the level of uracil misincorporation into DNA. The DNA damage was evaluated in young women's leukocytes with uracil glycosilase modified comet assay. Folate intake was evaluated on the basis of food diaries recorded in 2 months. The folate and B12 concentrations were evaluated in serum. Most of the studied individuals had diet deficient in folate. Folic acid supplementation (400 μg/day for 4 weeks) brought the folate intake much above the RDI level and the serum folate level in each individual was much above the deficiency range. The positive correlation (p=0, 00156) was found between DNA SSB and the amount of B12 in serum after folic acid supplementation. The uracil misincorporation was not correlated with folate level but there was a significant negative correlation (p=0, 05) with serum vitamin B12 concentration. The relationship occurred only after folate supplementation. This can suggest that high dietary folate intake is not sufficient to protect the leukocytes against uracil misincorporation if serum B12 concentration is not adequate.