It was an observational study.

VOA: special.2009.09.01

So when you put these observational studies together with a 'gold standard' clinical trial, the findings are overwhelming."

VOA: standard.2010.07.21

"In the observational studies we found that some of the B vitamins, like folic acid,were beneficial."

VOA: standard.2010.06.17

"I think there have been some observational,smaller studies that suggested the same thing.

VOA: standard.2010.07.21