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Avocado-soybean unsaponifiables (ASU)

A plant-lipid extract with some of the more interesting osteoarthritis evidence — and a hint of structure protection.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsJoint healthOsteoarthritis

ASU is a standardised extract of the unsaponifiable fractions of avocado and soybean oils (the part of an oil that will not turn into soap). Combined roughly one part avocado to two parts soybean, it is one of the few joint supplements with a "disease-modifying" signal rather than only symptom relief.

Key takeaways

  • A standardised avocado + soybean oil-fraction extract, rich in phytosterols; the studied product is usually Piascledine 300.
  • A meta-analysis of 4 randomised trials (664 patients) found less pain and better function than placebo, with a number-needed-to-treat of about 6.1
  • The benefit looks clearer for knee than hip osteoarthritis.1
  • Standard dose is 300 mg once daily; give it 2–3 months.

What it is

ASU is the "unsaponifiable" portion of avocado and soybean oils — the small residue rich in phytosterols (beta-sitosterol and others). In lab work it dampens inflammatory mediators such as interleukin-1 and supports cartilage cells (chondrocytes) and collagen synthesis, which is the rationale for a possible cartilage-protective effect on top of pain relief.

The evidence

A 2008 meta-analysis by Christensen and colleagues pooled 4 manufacturer-supported randomised trials (664 hip and knee OA patients, ~6 months). ASU 300 mg/day reduced pain and improved the Lequesne function index versus placebo, with significantly more "responders" (odds ratio 2.19) and a number-needed-to-treat of about 6; a subgroup analysis suggested knee OA responded better than hip.1 A separate 3-year hip-OA trial (ERADIAS) hinted at slower joint-space narrowing in a subgroup but missed its primary endpoint, so firm "structure-modifying" claims stay tentative. A Cochrane review of oral herbal OA therapies rates ASU among the better-supported options while noting the industry funding.2

Dose & how to use

The consistent trial dose is 300 mg/day of a standardised ASU (Piascledine-type), taken once daily with food. Effects build over weeks — trial it for about 3 months before judging.

Safety & who benefits

Generally well tolerated; occasional mild stomach upset. As it derives from soybean, people with soy allergy should check the product. Most useful for knee (and to a lesser extent hip) osteoarthritis, on its own or alongside the classic joint supplements.

Bottom line: one of the better-evidenced joint extracts — 300 mg/day of a standardised ASU is a reasonable, low-risk trial for knee (and hip) osteoarthritis.

References

Adult research summary for education, not a prescription. These are food supplements, not treatments for disease.

  1. Christensen R, Bartels EM, Astrup A, Bliddal H. Symptomatic efficacy of avocado-soybean unsaponifiables (ASU) in osteoarthritis (OA) patients: a meta-analysis of randomized controlled trials. Osteoarthritis Cartilage 2008;16(4):399–408. pubmed.ncbi.nlm.nih.gov
  2. Cameron M, Chrubasik S. Oral herbal therapies for treating osteoarthritis. Cochrane Database Syst Rev 2014;2014(5):CD002947. pubmed.ncbi.nlm.nih.gov

This article summarises nutrition science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.