Hi Chirly,
You are funny....There are some things I don't want to know either...ha!
I'm not familiar with MTHFR so I can't comment on it. However, I do know that some people have problems utilzing folate in the form of most dietary supplements. This is usually do to some genetic errors. When it comes to the "B" vitamins, you really need all of them. They act synergistically. Typically, they say if your MMA is elevated, it means your B12 is not being utilized and if the homocystine is high, it's a folate problem. However, you need more than folate to effect homocystine. And taking folate alone, can mask a b12 problem.
The main three B vitamins for homocystine are B12, folate and B6. There are bio-active or bio-available forms of these which have shown to be more effective. B12....methylcolbalamin form; B6....p-5-p form; and folate.....methlyfolate. You can get a prescription with all three. It's called Metanex. Or you can buy them individually, OTC. The Methlyfolate is hard to come by because the drug companies are trying to control it. There are a couple other vitamins that are involved but I cannot recall them at this point. But again, I don't know how much of this actually applies to your situation.
One of John's doctors stated that your blood serum levels of folate can be elevated but you may not be utilizing it so it stays in your blood and does not get to where it's needed. The bio-available vitamins do not need your body to convert them to usuable forms.
When we were working to restore John's health after his treatment, I had him on 5000mcg of Methly B12, 50 mg of p-5-p B6, 400 mcg folate and a B50 complex to round things out.
Here's a link on B12 deficiency that talks a bit about MMA.
http://www.aafp.org/afp/20030301/979.html
I think it's all very complex when it comes to figuring out what's missing or what will help. Even some of the better nutritionists have a difficult time putting all the pieces together. Knowing what's missing, and knowing why and how to correct it is whole another challenge.
Marlene