I am currently taking multivitamins that contain 400 mcg of folic acid and am wondering if it would be safe to take another 400 mcg of folic acid (800 mcg total)? I read that folic acid is essential before and during pregnancy for healthy growth. Are there any dangers?
I am so glad to hear that you are already planning for a healthy pregnancy. You are correct! Folic acid diminishes the chance of certain types of birth defects, including spina bifida. While there are no known risks of folic acid, the general recommendation is to take 400 micrograms a day, as you say, before and during early pregnancy. This is based on research that shows a 50 percent decrease in the incidence of spina bifida at that dose. Under normal circumstances, more isn't better. Moms-to-be who are at higher than usual risk of spina bifida are encouraged to take a higher dose—as much as 4000 micrograms (4 milligrams) a day—but that isn't recommended for the general population and should be done only with a medical prescription.
The only downside to taking higher than necessary amounts of folic acid is cost (which is minimal) and the rare problem that high doses of folic acid can hide the manifestations of vitamin B12 deficiency. But since 400 micrograms a day should be all you need, it makes the most sense to stick with the standard amount that has been shown to prevent spina bifida, rather than taking excess vitamins, since that hasn't been as well studied.
And don't forget to do the other actions to up your odds for a healthy pregnancy: avoid toxic exposures like cigarettes, alcohol, and drugs, and have a preconception appointment with your doctor or midwife so you can get individualized recommendations on taking the best care of yourself before and during early pregnancy. Best wishes for a happy and healthy future!