Just a quick one,

5gms of vegemite will actually provide 100 micro grams of folate. Tabs for pregnancy usually contain 500 micro grams.

Leafy green vegies are high in folate.
Many milks juices and cereals (including comercial breads) are fortified with Folate.

While taking folate pre conception and during first trimester has proven qualities, if you have a healthy diet, and aren't one of the un-lucky ones with MS all the way through, taking extra folate will probably do very little for you.

Any vitamins, if you take them in excess of what your body actually requires they just stop doing anything.