| Sleep apnea
I'm an American physician and can vouch for what johncolossus has said. His summary is a pretty good one. I don't know of any link to folate and sleep apnea per say, but folate is one of those vitamins/minerals that does the body good. As said above it reduces homocysteine levels which are related to heart disease and is used for red blood cell (RBC) production. Your body should be getting enough for RBC production if you eat green leafy vegetables without the need for supplements. It also prevents neurotube defects (things like spina bifida) if taken during the early parts of pregnancy. American doctors recommend a folate supplement for nearly all women of child bearing age since spina bifida is usually preventable. | 
And yet another word from our sponsors
