I'm new to this whole SNP thing. I have the 23andme test kit sitting right in front of me as I type this. I am wondering which SNPs have problems with folic acid and/or folinic acid? And I would appreciate detailed answers explains why that certain SNP has problems rather than just yes or no. For example it seems certain mutations of both MTHFR and MTHFS have problems with folinic acid, but for different reasons (which I don't understand well at all). I would also like to know whether these SNPs have to avoid folic acid and/or folinic acid entirely or if only moderate to large amounts cause problems. Also, with MTHFR is it only the conversion to from folinic acid to methylfolate that is inefficient, or are do they also have trouble using folinic for other functions?