Evaluating Medications and Supplement Products (cont.)

Medical Author:
Medical Editor:

What is a placebo?

A placebo is a biologically inert substance that does not have any effect on the disease under investigation Placebos are given to persons participating in double-blind controlled clinical trials. For example, a placebo can be sugar powder or salt placed in capsules that are made to look exactly like the medication being tested, so that neither the person giving the drug, or the person taking the drug know whether a placebo or the test drug is being administered.

What is a placebo effect?

A placebo effect is a beneficial response of a disease and its symptoms to a placebo. The placebo effect can be found in almost every clinical trial. For example, in all the randomized double-blind, placebo-controlled trials involving ulcer medications, a consistent number of placebo-treated patients will experience ulcer healing and symptom improvement. Thus the only way to prove that a test medication is effective is by demonstrating its superiority over a placebo.

What is an observational study?

An observational study is a retrospective analysis comparing the health status of one group of subjects (for example, women who took folic acid supplements) to another group (for example, women who did not take folic acid supplements). Observational studies can only provide circumstantial evidence. Conclusive proof of treatment benefit has to come from prospective, randomized, and placebo-controlled trials.

  • Example: Vitamin A is an antioxidant that was believed to be beneficial in preventing cancer and heart diseases. But randomized prospective placebo-controlled trials not only could not demonstrate any benefit of vitamin A, some studies actually found it harmful in some subjects.
Medically Reviewed by a Doctor on 10/16/2015