Searching for Clarity: A Primer on Medical Studies

[groovedaddy]

Everyone, it seemed, from the general public to many scientists, was enthralled by the idea that beta carotene would protect against cancer. In the early 1990s, the evidence seemed compelling that this chemical, an antioxidant found in fruit and vegetables and converted by the body to vitamin A, was a key to good health.

There were laboratory studies showing how beta carotene would work. There were animal studies confirming that it was protective against cancer. There were observational studies showing that the more fruit and vegetables people ate, the lower their cancer risk. So convinced were some scientists that they themselves were taking beta carotene supplements.

Then came three large, rigorous clinical trials that randomly assigned people to take beta carotene pills or a placebo. And the beta carotene hypothesis crumbled. The trials concluded that not only did beta carotene fail to protect against cancer and heart disease, but it might increase the risk of developing cancer.

It was “the biggest disappointment of my career,” said one of the study researchers, Dr. Charles Hennekens, then at Brigham and Women’s Hospital.

http://www.nytimes.com/2008/09/30/health/30stud.html?th&emc=th

[Avalux]

1. Science = facts.

Despite the shortcomings with clinical trials, especially Phase III randomized trials where variables cannot be tightly controlled, they are the best model for proving a hypothesis.

Anecdotal stories are not "proof"; they are simply subjective recounts of isolated cases.

[bananas]

2. Even clinical studies have to be viewed skeptically

due to publication bias, etc.