The term ‘nutraceutical’ (which has no official definition), is often applied to a dietary supplement used with the aim of preventing or treating disease. Although there is evidence from in-vitro trials that some supplements have effects on joint structure, such effects may not necessarily translate into clinical improvements. The authors of a systematic review published earlier this year attempted to answer the question of whether supplements have any effects on the clinical signs of osteoarthritis by examining the published literature.1
The review’s authors searched for published comparative trials (published in English or French) that assessed the effects of oral supplements in cats, dogs and horses. Only trials that assessed the clinical signs of pain or abnormal gait were considered. The trials included animals with naturally occurring osteoarthritis, but because of the few trials in horses, the review also included trials on induced osteoarthritis in that species.
Supplements used in the trials in the systematic review1
Cats: a combination of omega-3 fatty acids, green lipped mussel powder, glucosamine and chondroitin sulphate
Dogs: hydroxycitric acid; extract of Indian and Javanese turmeric; β glucans; gelatine hydrolysate; non-denatured type-II collagen alone or combined with hydroxycitric acid or with chromium nacinate; special milk protein concentrate; glucosamine and chondroitin sulfate; omega-3 fatty acids; and green lipped mussel powder
Horses: soybean and avocado unsaponifiables extracts; non-denatured type II collagen; chondroitin sulfate; combinations of oligoelements, amino acids and vitamins (AOV); combinations of myristoleic acid, glucosamine, methylsulfonylmethane, hydrolysed collagen and AOV
The review’s authors found 22 eligible trials: 1 in cats, 16 in dogs, and 5 in horses (2 of which were in a horse model of osteoarthritis). They systematically assessed the quality of the evidence, based on the reporting of methodology and results, the number of trial participants, the number of trials on a particular supplement, consistency of results across trials for the same supplement and demonstration of statistical significance.
Overall the evidence of efficacy of nutraceuticals in improving pain or gait abnormalities in osteoarthritis is poor. The exception is omega-3 fatty acids in dogs. Four randomised controlled trials in dogs that assessed supplementation with omega-3 fatty acids were considered high quality and showed a statistically significant effect on the clinical signs of osteoarthritis. However, the review’s authors did not describe the size of the clinical effects seen with omega-3 fatty acids in the trials.
In general, it is difficult to reach a conclusion about the efficacy of nutraceuticals in osteoarthritis because there are few published rigorous randomised controlled trials, they included a limited number of patients, and objective outcome measures were rarely used. Furthermore, a lack of standardisation of the doses of supplements and the duration of their use (ranging from 14 to 180 days in the trials) makes it difficult to compare different products. The low number of trials may be related to the fact that companies are not required to provide supportive scientific evidence in order to be able to market supplements.1
- Vandeweerd JM et al. Systematic review of nutraceuticals to alleviate clinical signs of osteoarthritis. J Vet Intern Med 2012; 26: 448–56. Link: http://www.ncbi.nlm.nih.gov/pubmed/22404506