MTHFR and hyperhomocysteinemia: For a homozygous person with a mutation MTHFR 677C => T the enzyme activity is reduced to 35% of the normal.20 A typical mutation in Europe occurs within the gene for MTHFR 677C => T, with different incidences between German (24.5%) and Italian (43.8%) populations.20 Moreover, it seems that this mutation and the reduced activity of the enzyme MTHFR are not connected with hyperhomocysteinemia if persons have balanced diet with optimal intake of vitamins (B6, B12 and folates).19