I have been doing a lot of research on the MTHFR gene polymorphism. Apparently around 35% of the population has this genetic mutation. Those that have this gene problem cannot convert synthetic folic acid (which is in everything!) into the active form --L 5 methyl-tetrahydrofolate. People that have this gene polymorphism don't clear heavy metals well. They have an increased risk of cancer (especially breast, colon, and gastric), and have a susceptibility to addiction. Around 98% of children with Autism Spectrum Disorder have at least one of the MTHFR gene mutations.
The following conditions are associated with the MTHFR gene polymorphism: cardiovascular disease, stroke, peripheral neuropathy, still births, pre-eclampsia, neural tube defects/cleft lip, depression, anxiety, IBS, fibromyalgia, chronic fatigue, dementia, migraines, schizophrenia, parkinson's, miscarriage, and infertility.
The biggest problem with this gene mutation is the inability to detoxify heavy metals. Symptoms of heavy metal overload include: social deficits, withdrawal, OCD, bi-polar disorder, schizophrenia, aggression, tantrums, fibromyalgia, colon/pancreatic cancer, liver/kidney problems, hair loss, premature graying, rashes, poor concentration, etc...
Here are some excellent resources for further reading:
MTHFR related health problems
Mark Hyman article on Folic Acid
Video lecture on MTHFR by Neil Rawlins, MD
List of MTHFR resources (also from Neil Rawlins, MD)
Dangers of folic acid supplementations (by Dr. Fuhrman)
Pub Med Studies on:
autism, autism, autism, psychiatric disorders, breast cancer,
A slide show from Kenneth Bock, M.D. on Autism/ADHD/Allergies/Asthma:
Oh, and the active form of folate is available online and in specialty pharmacies, but it is hard to find. There are several prescriptions with active forms of the B vitamins, such as Meta NX, Deplin (folate for depression), and Cerefolin (often prescribed for alzheimers and fibromyalgia). There is a prescription prenatal vitamin with methylfolate called Neevo.
Here is a Mothering.com discussion about real folate.
Here is an article linking folate blood levels to IgE allergies. Of course.