Glucosamine, chondroitin, Boswellia and MSM are popular dietary supplement ingredients for treating symptoms of osteoarthritis—worn joint cartilage. But some products don’t contain listed ingredients, are contaminated with lead, or do not break apart properly, according recent analyses by ConsumerLab.com, White Plains, NY.

In fact, 3 of 18 supplements (17%) for people selected for review failed testing, as did all four of the products for dogs and cats. Additional products that passed testing, including two for pets, were identified through ConsumerLab.com’s Quality Certification Program.

Twenty-nine percent of people who take multiple dietary supplements take a joint health supplement according to the latest ConsumerLab.com consumer survey. Sales of these supplements were approximately $900 million, according to 2012 figures from Nutrition Business Journal. Clinical studies suggest the combination of glucosamine and chondroitin can reduce moderate to severe knee pain due to osteoarthritis. Chondroitin may also significantly decrease pain due to osteoarthritis of the hands. Boswellia, sold as a proprietary extract such as 5-Loxin, has been shown to reduce symptoms of osteoarthritis, as well as ulcerative colitis. The evidence for MSM in treating osteoarthritis in people remains preliminary.

Among the 18 products for people selected by ConsumerLab.com 15 met quality standards and labeling requirements. One product contained just 51.6% of the Boswellia promised on the label, based on its content of boswellic acids. Another product contained only 84.6% of its listed chondroitin sulfate and exceeded limits for lead in a daily serving. The tablets of a third product would not properly break apart to fully release its ingredients. Interestingly, two of the products which failed testing were also the most expensive products reviewed.

Among the products for dogs and cats, one contained just 16% of its listed amount of chondroitin. Two contained only 71% and 76%, respectively, of their listed glucosamine. A fourth product contained 35% more MSM than listed on its label.

The Product Review of Joint Supplements (for people) is available online.

The Product Review of Joint Supplements for Dogs and Cats is available online in a separate report.