mrsD, adding to your list of reliable sources of information, the Cochrane Collaboration (http://www.cochrane.org/) is also worth checking out.

It is a not-for-profit group of health professionals, epidemiologists and biostatisticians which accepts no funding from any private source.

What it does is to pool the results of clinical trials of the effectiveness of many health/medical procedures and then do a systematic review/meta-analysis (different terms for the same idea) of them - assessing how convincing the evidence is. Sometimes it turns out that the meta-analysis shows that there is good evidence that a procedure is effective, other times it turns out that the evidence is poor.

Cochrane is searchable and may help members to decide how strong the evidence is for the efficacy of a procedure that a health professional may recommend.