Mobility dog foods are based on wobbly evidence

Mobility impairment due to osteoarthritis is a common canine disease. Affected dogs are reluctant to walk and may show symptoms of chronic pain and lameness. Osteoarthritis is a degenerative and inflammatory condition caused by degradation of cartilage matrix in the joints. The marketplace offers a wide variety of mobility dog foods claiming to support joint health. Veterinary mobility foods are indicated for the treatment of canine osteoarthritis.

Effective supplements provoke better joint function

The mobility claims are linked to supplements (functional ingredients) from a pool of some 13 ostensible candidates. Effective supplements provoke better joint function in dogs than a placebo as substantiated by meaningful, statistically significant and reproducible effects. So far, efficacy evaluation comprised treatment rather than prevention of osteoarthritis. Clinical trials must be double-masked to neutralise the generally observed placebo effect in dogs with osteoarthritis.

Most common additions were ineffective

The most commonly used additions, glucosamine and chondroitin sulfate, were ineffective in 4 out of 5 double-blinded, placebo-controlled trials in osteoarthritic dogs. In 5 such trials, greenlipped mussel had no or meaningless effect. Curcumin showed unconvincing efficacy in 1 study. Boswellia resin was only tested in an open, non-controlled trial. Green tea alone, methyl sulfonyl methane, devil’s claw, mulberry and grape extracts are all untested in dogs.

Impact of fish oil on osteoarthritic dogs

In 4 randomised, double-blind, placebo-controlled trials the impact of dietary fish oil on the severity of clinical signs in osteoarthritic dogs was assessed. On a scale of 0-10, the mean placebo-corrected improvements were 0.1, 0.4, 0.8 and 4.2 units so that clinical relevance is open to dispute. Gelatin hydrolysate and beta-1,3/1,6-glucans had positive effects of 1.3 and 0.5 units, but reproducibility is unknown. The 3 substances likely have different mechanisms of action, implying that the combination works synergistically, but this remains to be demonstrated.

Fish oil, gelatin hydrolysate and beta-1,3/1,6-glucans each showed a small, positive effect on osteoarthritic signs. Does the effect size seen experimentally extend to that of mobility foods using the ingredients concerned? In other words, are preparation and dosing identical for trial and food, and does functionality survive pet food processing? These questions may be answered by the pet food manufacturer.