MTR and Alzheimer disease: The observed strong link between reduced folates and reduced vitamin B12 levels (ls=0.99) is also known [1,8], and this condition is likely to foster an increase in hcy levels (ls=0.82) that is often seen in AD individuals [1–10], likely because of vitamin B12 is a cofactor required by the MTR/MTRR complex during the conversion of hcy to methionine (Figure 1).