ASU (Avocado Soybean Unsaponifiables) for Dogs: Evidence

ASU — avocado/soybean unsaponifiables — is a plant-sterol extract added to some of the best-known dog joint supplements, usually alongside glucosamine and chondroitin. In dogs, ASU on its own has been tested only in a laboratory model of arthritis, where it reduced cartilage damage in 16 dogs. We found no clinical trial of ASU alone in pet dogs with naturally occurring osteoarthritis. The human evidence is modest and comes from a specific drug formulation.

Key takeaways

• In 16 dogs with arthritis induced by cruciate ligament transection, ASU (10 mg/kg a day for 8 weeks) reduced cartilage lesions and bone changes vs placebo. That is structural evidence in a surgical model, not pain relief in pet dogs.
• Clinical trials in pet dogs tested multi-ingredient products; one compared a 10-ingredient supplement containing ASU with the NSAID mavacoxib, without a placebo.
• In people, a 2008 meta-analysis found modest pain benefits, mainly in knee osteoarthritis, from small industry-funded trials.
• ASU is a lipid extract, so its amount per chew is often small and rarely matched to studied doses.
• Omega-3, green-lipped mussel and UC-II have stronger canine evidence.

What is ASU?

When avocado and soybean oils are processed with alkali, most of the oil turns into soap. The small fraction that does not — the “unsaponifiables” — is rich in plant sterols such as beta-sitosterol. ASU is typically made from one part avocado to two parts soybean unsaponifiables. In laboratory studies, ASU reduces inflammatory signals and cartilage-degrading enzymes in joint cells and supports cartilage matrix production. A standardized ASU product (Piascledine) is approved as a drug for osteoarthritis in people in some countries.

What the canine evidence shows

Surgical model: less cartilage damage

In a 2009 study, osteoarthritis was induced in the knee of crossbred dogs by cutting the anterior cruciate ligament. Eight dogs received ASU at 10 mg/kg a day by mouth for 8 weeks and eight received placebo. Dogs given ASU had smaller cartilage lesions on the tibial plateau, fewer and smaller changes in the bone beneath the cartilage, and less inflammation in the joint lining; the researchers linked this to lower levels of enzymes that break down cartilage.

This is careful laboratory work, but it measured tissue damage at the end of the study in dogs with a surgically created joint injury. It did not measure pain, lameness or quality of life, and it does not show what ASU does for an older pet dog with long-standing arthritis.

Pet dogs: combination products only

• A randomized, double-blind 2025 study in 20 dogs with osteoarthritis compared a supplement containing fish oil, ASU, turmeric, devil’s claw, Boswellia, willow bark, black pepper and astaxanthin with the NSAID mavacoxib for 90 days, and found similar improvements in pain, lameness and joint fluid. With about ten actives and no placebo group, it cannot say what ASU contributed.
• Some popular glucosamine–chondroitin products add ASU. The placebo-controlled evidence for glucosamine–chondroitin products is weak — see Does glucosamine help dogs with osteoarthritis?.

What the human evidence shows

A 2008 meta-analysis of randomized, placebo-controlled trials in people with hip or knee osteoarthritis found that ASU reduced pain and increased the number of patients responding to treatment, with a better chance of success in knee than hip osteoarthritis. The authors cautioned that the trials were small, the effects were small to moderate, and all the trials were industry-funded. Human doses (300 mg a day of a specific drug formulation for an adult) also do not translate directly to dog chews.

Safety

ASU was well tolerated in the dog studies. It is derived from soybean, so dogs with a diagnosed soy allergy may be at some risk, although the sterol fraction contains little protein. As with any joint supplement, the bigger risk is relying on it while pain goes untreated.

How to read the label

• Is ASU listed with an amount in mg? The laboratory study used 10 mg/kg a day — about 100 mg for a 10 kg dog or 300 mg for a 30 kg dog.
• What carries the formula? In most products ASU is an add-on to glucosamine and chondroitin. If you are choosing for evidence, check EPA/DHA, green-lipped mussel or UC-II amounts with the joint dose checker.

For a full checklist, see How to check a dog joint supplement label.

Dog Supplement Facts evidence status

INSUFFICIENT

ASU has laboratory-model evidence in dogs and modest, industry-funded human evidence, but no clinical trial of ASU on its own in pet dogs with osteoarthritis. Under our rating rules, it is rated insufficient.

When to see a veterinarian

Limping, stiffness after rest, reluctance to jump or use stairs, and licking at joints are signs of pain. Weight control, exercise plans, anti-inflammatory drugs and anti-NGF antibody therapy have much stronger evidence than any supplement.

Related Dog Supplement Facts content

• MSM and Hyaluronic Acid for Dogs’ Joints
• Green-Lipped Mussel for Dogs
• Dog Joint Supplements: What Matters
• Best-selling dog joint supplements vs the evidence

References

1. Boileau C, et al. Protective effects of total fraction of avocado/soybean unsaponifiables on the structural changes in experimental dog osteoarthritis: inhibition of nitric oxide synthase and matrix metalloproteinase-13. Arthritis Res Ther. 2009. PMID: 19291317. https://pubmed.ncbi.nlm.nih.gov/19291317/
2. A randomized, double-blind, controlled study on the efficacy of an oral dietary supplement containing fish oil, ASU and phytotherapeutic extracts in canine osteoarthritis. Front Vet Sci. 2025. PMID: 41737916. doi:10.3389/fvets.2025.1693838
3. Christensen R, et al. Symptomatic efficacy of avocado–soybean unsaponifiables (ASU) in osteoarthritis (OA) patients: a meta-analysis of randomized controlled trials. Osteoarthritis Cartilage. 2008. PMID: 18042410. https://pubmed.ncbi.nlm.nih.gov/18042410/
4. Barbeau-Grégoire M, et al. A 2022 systematic review and meta-analysis of enriched therapeutic diets and nutraceuticals in canine and feline osteoarthritis. Int J Mol Sci. 2022;23(18):10384. PMID: 36142319. doi:10.3390/ijms231810384