Many people enthusiastically tried the so-called Feingold Diet, but the enthusiasm waned as the years went on and "some very well-done randomized controlled studies" questioned Feingold's theory, says Deborah Pearson, Ph.

CNN: FDA weighs food dye, hyperactivity link

These are the kinds of big, randomized, controlled studies that the U.S. Food and Drug Administration requires before a new drug is approved.

FORBES: Magazine Article

That research, however, typically didn't involve randomized, controlled studies.

WSJ: Fish Oil Provides Little Benefit for Pregnant Women

Medical research commonly employs three kinds of study designs: observational studies, randomized controlled trials (RCTs), and metaanalyses.

FORBES: Clinical Trial Advice For Investors From Two Pros

Twenty-one of the studies included in the review were randomized controlled trials, which are considered the gold standard for scientific research.

CNN: Can herbal supplements treat anxiety?

But randomized controlled clinical trials also are used to prove benefit in big drug studies.

FORBES

All of the studies ran for at least a year, and all were randomized controlled trials, the most rigorous type of study.

FORBES: Should Everyone Take Statins?

In the accepted hierarchy of evidence generation, the results of a randomized, controlled clinical trial usually take precedence over other forms of evidence such as meta-analysis and observational studies.

FORBES: Glaxo Alleges Errors In Nissen's Critique Of FDA's Handling Of Avandia