And why would I need a DNA test? I'm confused about the methylation stuff :-)

It has been found that many people have this error, and cannot methylate B12 and folic acid to their active forms so they can work properly in the body.

Let's look at numbers. It was thought 10% at least have this error (called MTHFR polymorphism), but now the number is increasing and up to 30% is now suggested by some new research.

What does that mean? Take a stadium full of people. Average size now is 100,000. 10% would be 10,000 in that stadium would have this genetic error. One of the first signs of inadequate B12 is neurological. Over time having low B12, would lead to insomnia, elevated homocysteine, and damage to arteries and hence cardiovascular events. Anemia comes rather late in low B12 patients. But it does arrive eventually.

If you have this error, your body cannot perform certain functions. When long standing, it affects the spinal cord and is called :
http://en.wikipedia.org/wiki/Subacut...of_spinal_cord

This happened to many thousands of Japanese in the early '70's from common use of a drug called clioquinol. (it was taken off the market here at that time). Hence the Japanese have done much research on B12 and as a result have a higher cut off for "normal" than our 400pg/ml. Many people in Japan died or were permanently maimed/blinded by this event.

We know about the methylation issues now, but 15 yrs ago it was not common knowledge. The work on the human genome has been one reason we have more understanding.

Methylation is the moving of a --CH3 group around the body to do many metabolic jobs.
http://en.wikipedia.org/wiki/Methylation
If you search "methylation" on Google you will find quite a bit of
complex chemical papers and sites. But here we deal mostly with the methylation of B12 and folic acid.

Remember we are chemical factories. And mRNA delivers information to the cells, to make new compounds to do many jobs, and this involves that methyl group (one carbon and 3 hydrogen molecules).