Clinical trials too.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2875636/
A food supplement containing fish oils, urtica dioica, zinc, and vitamin E (Phytalgic�) for osteoarthritis (OA) has now been tested in a placebo-controlled trial for 3 months and according to the authors has a very large clinical effect, considerably larger than that of any other known product. Even experts endorsing nutraceuticals for OA symptoms would probably agree that a nutraceutical with an effect size above 0.5 is rarely seen. Despite our concerns about the fact that trial registration took place after the study was completed and the likelihood that patients would note the taste of fish, a circumstance that would lead to detection bias, we consider these data promising though with a high risk of bias.
.....we are now faced with some very promising results of Phytalgic� , and further experience is needed to show whether this product on a larger scale will become a relevant treatment option for OA . As previously pointed out, the largest studies and the studies that are strictly monitored by good clinical practices are usually directly sponsored by the product manufacturers . A fully independent analysis of a product like Phytalgic� would require funding from official organizations (for example, the National Institutes of Health, which indeed needs reshuffling of its priorities). These initial data on Phytalgic� would seem to justify such action. If these data are confirmed, a goldmine has been struck and OA therapy is in for dramatic changes.