Green-lipped mussel (Perna canaliculus) is a New Zealand mussel sold as a powder or as an oil extract, nearly always for the joints. In most trials in dogs with osteoarthritis, the group that took it improved slightly more than the placebo group, mainly on the vet's and the owner's scores. Objective measurements are few, one low-dose trial found nothing, and products vary so much that one trial's result does not transfer to every jar on the shelf.
A New Zealand mussel, sold in three forms
The species lives only on the coasts of New Zealand, where it has been farmed for decades. Medical interest began when people noticed that coastal Māori communities, who ate a lot of these mussels, seemed to have less arthritis than communities inland. From the 1970s onwards came laboratory, animal and human studies, as a 2018 review of veterinary trials summarises.
It reaches the market in three main forms. Freeze-dried whole mussel powder is the meat, freeze-dried and ground, and most trials in dogs have used powdered preparations. A lipid extract is the stabilised fat fraction of the mussel, sold in capsules or as an oil; Lyprinol and PCSO-524 are names of this kind of extract. The third form is a blend with other ingredients, for example krill oil, or glucosamine and chondroitin.
What is thought to be the active part?
The mussel contains a mix of fats: EPA and DHA (the same omega-3s found in fish oil), less common omega-3s such as eicosatetraenoic acid, furan fatty acids, sterols, and antioxidant pigments such as carotenoids. Most of these compounds are probably made by the microalgae the mussel feeds on. The 2018 review links the effect to its omega-3s, EPA and DHA, and names other fats, bioactive peptides and the furan fatty acids as possible contributors.
The proposed mechanism is the same as for omega-3. Its fatty acids compete with arachidonic acid for the enzymes that make prostaglandins and leukotrienes, the signals that keep inflammation going. A critical review of the Lyprinol extract concludes that, as an anti-inflammatory, there is little to choose between this extract and fish oil in human studies, and that the benefits seen have been small.
The powder, though, contains little EPA and DHA: the product in the Finnish trial described below declared more than 500 mg of EPA and more than 400 mg of DHA per 100 g, a little under 1%. At the starting dose for dogs up to 40 kg (four 500 mg capsules a day), a dog received about 20 mg of EPA and DHA, whereas fish oil studies work in grams. If the mussel works, it is probably not only because of its EPA and DHA.
The trials in dogs
All the trials were in dogs with osteoarthritis or degenerative joint disease. In a 2003 double-blind trial, 31 dogs ate food with 0.3% mussel powder or the same food without mussel for 6 weeks. The mussel lowered the vet's arthritis score, with improvements in joint pain and swelling. Crepitus and range of movement changed no more in one group than in the other.
A 2006 trial gave 81 dogs with mild or moderate joint disease an extract or a placebo for 8 weeks. At 28 days there was no difference from placebo. At 56 days more dogs had improved in the extract group, and the musculoskeletal examination score was only slightly better, on the borderline of statistical significance. All the dogs then took the extract for another 8 weeks, and the difference disappeared because the former placebo group improved too. The authors conclude that a long course may be needed before improvement shows. There were no signs of toxicity.
A Finnish double-blind trial set the mussel against both a placebo and carprofen, a veterinary anti-inflammatory, in 45 dogs over 8 weeks. The mussel beat placebo on mobility rated by the vet, on the chronic pain index scored by the owner and on the pain scale. On the force plate, the objective measure of how much weight the dog puts on its legs, the difference from placebo was not significant. Carprofen worked better than the mussel.
A 2002 trial lasting 12 weeks, reported in both the 2018 review and the Lyprinol review, found no effect at a low dose (about 11 mg/kg a day). Owners and vets saw a slight improvement in every group, placebo included, and the Lyprinol review offers the low dose as an explanation.
A 2013 study fed 23 dogs a balanced diet for 30 days and then a balanced diet enriched with mussel for 60 days. Weight-bearing measured on a force plate improved during the mussel phase and not during the first phase. There was no parallel placebo group, and the authors accept that the balanced diet alone may have contributed.
In a 2024 trial in dogs with hip osteoarthritis, funded by the product's manufacturer, the mussel extract came combined with krill oil, so the trial cannot say how much of its result belongs to the mussel. Among the 101 dogs, both the blend and meloxicam, an anti-inflammatory, improved weight-bearing on the force plate at 6 weeks more than placebo (sunflower oil) did.
The 2022 systematic review with meta-analysis of osteoarthritis in dogs and cats placed the mussel trials among the omega-3-based products, which showed the clearest effect on pain. That is reasonable support, but almost all of these studies are small and run for a few weeks or months, and most depend on subjective scales filled in by the owner or the vet.
In people, a 2006 systematic review found weaker results: only two of five randomised trials of freeze-dried powder showed a benefit in osteoarthritis or rheumatoid arthritis.
Why products are not all the same
According to the 2018 review, heating the mussel destroys its activity, so drying it and adding it to food have to be done with care. The Lyprinol review describes how, in the early years, most of the activity was lost to heat or to freeze-drying, and says some older studies probably used preparations with no active compounds. The 2006 review in people points to the fatty acids not being stabilised as a possible cause of its mixed results.
Each trial also used a different preparation (powder, extract, blend) and expressed the dose in its own way, which makes fair comparison hard. Look for products that state which form of mussel they contain, where it comes from, how it has been processed and how much each serving provides.
Amounts tested in trials
According to the 2018 review, the animals studied (dogs, cats and horses) improved on 4 to 49 mg/kg a day, depending on the formulation. The dog trials above gave these amounts:
| Study | Dose | Result |
|---|---|---|
| 31 dogs, 2003 | 0.3% powder in dry food | Better arthritis score |
| 81 dogs, 2006 | 22 to 37 mg/kg a day of extract | More dogs improved at 56 days |
| 45 dogs, 2009 | 20 to 49 mg/kg a day for 10 days, then half that | Better than placebo on pain scales, not on the force plate |
| 2002 trial | about 11 mg/kg a day | No effect |
Agree the amount with your vet, especially if your dog already takes painkillers.
Allergies and other precautions
The trials in dogs described no relevant adverse effects: the 2006 trial found no signs of toxicity, the Finnish trial detected no side effects linked to the mussel, and the 2024 trial recorded no unexpected adverse effects and no blood test changes outside the normal range. The 2018 review cites a study in rats given 2 to 8 g/kg a day without problems, far above the doses in use. If vomiting or diarrhoea start when you begin giving it, stop and let the vet know.
Green-lipped mussel is a mollusc. If your dog has a diagnosed food allergy, or has ever reacted to fish or shellfish, ask the vet before giving it.
There is also a published case of a 54-year-old woman who developed eye, nose and bronchial symptoms from breathing in the mussel powder she was giving her dog. Her antibodies recognised actin, tropomyosin and paramyosin, proteins already known as allergens in other species, among them a clam and an abalone. If you are allergic to shellfish, avoid handling the powder or use a form in capsules.
Sources
- Greenshell Mussels: A Review of Veterinary Trials and Future Research Directions. Veterinary Sciences, 2018.
- Lyprinol: is it a useful anti-inflammatory agent?. Evidence-Based Complementary and Alternative Medicine, 2011.
- Influence of green lipped mussels (Perna canaliculus) in alleviating signs of arthritis in dogs. Veterinary Therapeutics, 2003.
- Clinical efficacy and tolerance of an extract of green-lipped mussel (Perna canaliculus) in dogs presumptively diagnosed with degenerative joint disease. New Zealand Veterinary Journal, 2006.
- Evaluating Complementary Therapies for Canine Osteoarthritis Part I: Green-lipped Mussel (Perna canaliculus). Evidence-Based Complementary and Alternative Medicine, 2009.
- Effect of a diet enriched with green-lipped mussel on pain behavior and functioning in dogs with clinical osteoarthritis. Canadian Journal of Veterinary Research, 2013.
- Evaluation of the comparative efficacy of green lipped mussel plus krill oil extracts (EAB-277), Biota orientalis extracts or NSAIDs for the treatment of dogs with osteoarthritis associated pain: a blinded, placebo-controlled study. Frontiers in Veterinary Science, 2024.
- A 2022 Systematic Review and Meta-Analysis of Enriched Therapeutic Diets and Nutraceuticals in Canine and Feline Osteoarthritis. International Journal of Molecular Sciences, 2022.
- Systematic review of a marine nutriceutical supplement in clinical trials for arthritis: the effectiveness of the New Zealand green-lipped mussel Perna canaliculus. Clinical Rheumatology, 2006.
- Identification of New Potential Allergens from Green-lipped Mussel (Perna Canaliculus). Iranian Journal of Allergy, Asthma and Immunology, 2022.