Folic acid vs folate
The terms folate and folic acid are often used as if they were the same thing. But they differ chemically. They also differ in the way they influence processes in our body.
Dr. Wright wrote a good article about the difference between the two: http://www.tahomaclinicblog.com/folic-acid/.
This is a piece of that article:
While human and animal cells cannot use the folic acid molecule itself in their normal metabolic processes, human cells (principally the liver) can transform folic acid back into many of its metabolically useful folate forms. That’s why folic acid—despite not being found in food—can do so much nutritional good, the best-known example being the prevention of birth defects including spina bifida, cleft lip, and cleft palate.
As we grow older, though, our bodies are increasingly slow at transforming folic acid into usefully metabolized folates. That’s probably why scientists are finding that folic acid (not folate) is associated with cognitive decline in the elderly. Some of these studies have shown significantly elevated levels of un-metabolized (and therefore not useful) folic acid building up in the bloodstreams of supplemented older individuals.
In addition to worsening folic acid metabolism with age, there are also a significant number (as high as 5 percent or more in some populations) of survivable human genetic defects of folate metabolism which make it more difficult or, in some circumstances, impossible for sufferers to make metabolic use of folic acid.
Folate was originally isolated from brewer’s yeast and spinach in the 1930’s. So you can simply eat either to get the real thing. Folate is found in more foods than just brewer’s yeast and spinach.
In books as well as on sites, mostly the term folic acid is used for either folate or folid acid. It can be hard to figure out which one is actually used.