Containing silicate minerals including calcium, magnesium, potassium, sodium and aluminum, among others, the combination was discovered around 30 years ago and is marketed in supplement form by Vancouver company Sierra Mountain Minerals, under the name SierraSil.
It was introduced in Europe in June 2004.
While other joint health supplements like chondroitin and glucosamine reduce pain by rebuilding cartilage, an earlier mechanism of action study indicated that SierraSil works by inhibiting the gene that causes inflammation.
The eight week, double-blind study involved 107 participants, all with mild to moderate osteoarthritis of the knee. They were divided into four groups: one group received 3g of SierraSil a day; one received 2g of SierraSil; one received 2 grams of SierraSil plus 100mg of botanical cat's claw extract; and the last group received a placebo.
The researchers, led by Marc Miller of the Center for Cardiovascular Sciences at Albany Medical College, decided to include cat's claw extract in the study since the Amazonian vine has a long history of use for joint pain and inflammation, and earlier in vitro studies suggested a complementary effect when used in combination with SierraSil.
The researchers measured the effectiveness of the interventions using the WOMAC scale (Western Ontario and McMaster University Osteoarthritis Index). They also measured a visual analog score (VAS) for pain, use of 'rescue' medication (paracetamol), and tolerability.
While all four groups showed an improvement in WOMAC and VAS at the end of the eight weeks, the WOMAC scores of the three SierraSil groups improved by between 38 and 43 percent, compared to 27 percent for the placebo group.
The improvement was also faster in the SierraSil groups: in just one or two weeks, their WOMAC scores were already significantly better, and the 38-43 percent improvement was realized in just four weeks.
VAS was improved in all four groups in four weeks, but the researchers said it was "significantly greater" in the SierraSil groups. Those taking the herbomineral combination and high dose SierraSil used 23 to 28 percent less rescue medication.
"Given concerns with the risks of cyclo-oxygenase inhibitors and the reported slow onset of benefits with glucosamine, this natural product approach may offer a valuable alternative to patients with joint pain and dysfunction," wrote the researchers.
In particular, they noted that participants did not display adverse effects to the intervention. "As this mineral supplement is relatively unknown it was important to evaluate safety as well as efficacy," wrote the researchers.
However the researchers did concede that there were some drawbacks to the study - notably that participants in the placebo group experienced some benefit, albeit not as great as those taking SierraSil. They said that this could be due to the participants' expectation that all the groups were taking something that would help with their condition - although this was clearly not in the instructions.
Also interesting was a sudden, unexpected improvement in the placebo group in the sixth and eighth week of the study. Although this could not be fully explained, the researchers said that it may be due to the greater use of rescue medication by the placebo group having an impact on their WOMAC scores.
"Total consumption of rescue medication was determined and so it is not possible to link changes in rescue medication to perceived changes in disease activityon a weekly or monthly basis," they wrote.