Pierre Le Bars and his colleagues wanted to test if Ginkgo biloba could be used to safely treat symptoms of dementia in patients with Alzheimer's, so they set forth on creating a rather standard, time-tested experimental design -- a placebo-controlled, double-blind, randomized trial with a fairly large sample size (309). Great care was taken to control extraneous variables and prevent bias, which is exactly what makes this such a good study.
Since Le Bars and company only wanted to test for the effects of Ginkgo biloba on patients' symptoms of dementia, they only selected patients with no other serious medical problems. This is an important control that helped the scientists make sure that no other condition was either negatively or positively affecting the patients' symptoms. Le Bars and his colleagues also controlled for the placebo effect, which is a phenomenon that causes some people to have either perceived or real improvement in a medical condition even though the treatment has no real pharmacological effect. They did this by giving part of the sample a placebo (a sham medicine containing no active ingredients) whilst telling the patients they are receiving Ginkgo biloba. This group is known as the control group, while the group that actually receives the Ginkgo biloba is known as the experimental group. This allows the researchers to compare the two groups. Ginkgo biloba could only be said to have a real benefit to these patients if it performs significantly better than the placebo. If it works equally well, than taking Ginkgo biloba could be said to be no better for dementia than taking sugar pills.
Le Bars and the other researchers were also aware that they had to be careful not to allow bias to slip into the study and skew the results. To do this, they implied a tried-and-true technique: they double-blinded the study. Blinding a study simply means that you keep which group is getting the placebo and which is getting the real thing a secret to the patients. This prevents the patients who are getting the placebo from knowing, therefore allowing the placebo effect to work. Double-blinding a study means that both the patients and those administering the treatment don't know which is placebo and which is not. This prevents the researchers from either consciously or subconsciously giving away any hints to the patients, and is further protection from bias. Le Bars, et al. also prevented bias by utilizing standardized tests for dementia that were applied in a consistently-controlled manner. So, this study was set up in a fashion that made it all-but-impossible to influence one way or the other, as neither the researchers nor the patients had a clue who was getting the real thing and measurements were taken in the exact same manner every single time.
The fact that 309 subjects were used in this study also adds to its validity, because one cannot perform meaningful statistical analysis on a small sampling of subjects. With a small sample size there is more of a chance that outliers will skew the results, there is less certainty that the selected individuals represent the general population, and there is more of a chance that extraneous variables enter into play in a significant role.
So, what did Le Bars and his crew find? Astonishingly, what was at the time most often dismissed as a bogus remedy actually was found to have a significant effect on patients already suffering from dementia. By the end of the 52-week study, the experimental group fared much better than the control group. In fact, the control group continued to decline while the experimental group's symptoms actually improved over the year. What was once pseudoscience is actually being taken seriously in the scientific community now because of this evidence. That doesn't mean it's all over, though. Other scientists are still having a bit of trouble replicating the study, and studies that investigated Ginkgo biloba's effects on preventing the onset of dementia have come up empty handed. Clearly, more work needs to be done, but the important part of the story is that this natural remedy is being taken seriously by the scientific community because people playing by the rules of science found something very interesting. This is predominantly because the scientific community, as well as the mind of the individual scientist, is primed to change its views when new, credible evidence is presented.
Le Bars, P.L., M.M. Katz, N. Berman, T.M. Itil, A.M. Freedman, and A.F. Schatzberg. 1997. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. North American EGb Study Group. The Journal of the American Medical Association 278(16):1327-1332. (PDF)