How was the information gathered?
Compounds included in the report:
- are taken by mouth or applied to the skin
- have been tested in at least one RCT
- could be sourced in June 2011 from a national high-street retailer or through a UK-based internet supplier (overseas retailers were included only where an address and contact details were provided and their website stated that they ship to the UK).
The information on compounds is based on evidence from randomised controlled trials (RCTs). Evidence was found and evaluated by experts in the fields of rheumatology, complementary medicine and nutrition, and it has also included input from a patient representative. They considered trials where the compound was compared with a conventional treatment or a placebo (a dummy pill which doesn’t contain any active ingredient).
They only found evidence from RCTs for 31 compounds. Many of those studied have only been tested in a single or just a few studies, which makes it difficult to be sure whether they work or not.
We’ve also only included trials in which results have been analysed on an ‘intention to treat’ basis. This means that if a participant is randomly allocated to receive ‘treatment A’, their results are analysed as if they received that treatment (even if they decided not to take the medication). This is the best method of analysis to avoid bias.
If several trials have been conducted, we’ll often summarise the information from a published review, including the proportion of participants withdrawing and the main reported side-effects from individual studies.
What are randomised controlled trials (RCTs)?
RCTs give the best type of evidence on whether any treatment works. Participants (people taking part in trials) in RCTs are randomly allocated to one treatment group. At the end of the study, results are evaluated according to whether participants on a new treatment, for example, had a better outcome than participants on an existing treatment.
RCTs of complementary medicines often use a placebo to allow the effect of treatment to be compared when the patients don’t know which treatment they received.
Types of study where participants choose the treatments they take are more difficult to interpret than RCTs because participants with more serious disease might have opted for one treatment and others with milder disease another. Also, participants who choose their treatment do so because they believe it’ll be effective, which might influence how they respond to it and evaluate it.