Well, in many of us this mutated gene prevents the body from converting folic acid into folate - the form of vitamin B9 that our body needs. Methylated folic acid found in some supplements is folic acid that has been converted prior to consumption into a bioavailable form our body can use, thus skipping the conversion step before it enters our system.
See the down and dirty explanation in this video:
Perhaps then, it is better to get our nutrients from fresh fruits and vegetables that contain these important building blocks of life.
However, these days due to many environmental factors the soil that helps grow these vital fruits and vegetables is lacking many of the nutrients we count on to sustain us. Thus, perhaps the only option left to us is to supplement with fortified foods.
Perhaps not yet, but if the soil quality does not improve a future where the soil will no longer sustain us might be not too much of a leap.