Flex-a-min is a daily multivitamin that claims to protect the joints and cartilage from degradation, a symptom that commonly occurs in people with weak or brittle bones, called osteoporosis. It claims to reverse this process by increasing joint lubrication and providing "structural support", though it does not explain how it prevents degradation of the joints or cartilage. Chemically, Flex-a-min is nearly identical to Osteo Bi-Flex, a popular joint health supplement purported as the "Most Recommended Joint Health Supplement" in the United States.
Flex-a-min contains glucosamine HCI and a proprietary blend of chondroitin sulfate complex, methylsulfonymethane and boswellia serrata extract.
Here's the bad news: only one of its ingredients may improve joint function. According to several studies, glucosamine has been shown to reduce joint pain specifically caused by osteoarthritis, a form of arthritis. Repeated studies have shown it also reduces swelling and stiffness caused by the condition, with improved joint mobility in people diagnosed with OA of the hip or knee. However, a 2006 trial funded by the National Institutes of Health shows that it isn't effective for other forms of arthritis or joint pain.
Flex-a-min's other ingredients---chondroitin and boswellia serrata extract specifically--have only been proven through anecdotal evidence to prevent joint pain, and are not considered effective joint health ingredients. Furthermore, none of its ingredients have been shown to affect the quality of healthy cartilage.
Some minor side effects have been reported. This may include stomach upset, heartburn, bloating, diarrhea and stomach cramps. Glucosamine can also lessen the effects of insulin drugs, making it potentially unsafe for diabetics.
Flex-a-min may only improve the joint pain associated with osteoarthritis. Its effectiveness in people suffering from joint pain not caused by this condition is unclear.