Twenty years ago, avocado soy unsaponifiables (ASU) were the latest thing for osteoarthritis in the horse. It subsequently fell out of favor as other new supplements became available. Does ASU still have a place?
◆︎ What is ASU?
ASU is the fraction of fats and oil that do not form soap or glycerin upon processing. It consists mostly of phytosterols, such as beta-sitosterol. ASU includes the phytosterols from avocado oil and soybean oil.
◆︎ What does it do?
The phytosterols reduce inflammation. Although it’s most widely used as a nutraceutical for osteoarthritis, it also reduces inflammation throughout the body.
◆︎ Are there studies about its effectiveness?
The studies show that oral supplementation with ASU affects the articular cartilage, which covers the bone in the joint. It does this by:
1) reducing the damage to the cartilage by wear and tear, and
2) helps repair the cartilage that has already been damaged.
An important caveat is that if you already have damage to the underlying bone, supplementation with ASU will most likely not be as helpful as you wish.
◆︎ Why don’t we hear more about ASU?
ASU is most effective in the early stages of arthritis. That also coincides with the time period that there are few signs of the degenerative processes occurring.
Although ASU can help maintain healthy articular cartilage, it does not significantly relieve the pain. Because of this, it is most frequently sold as a blend with other supplements, such as glucosamine, MSM, or hyaluronic acid. It can also be combined with Mov-Ease, quercetin, or resveratrol.
Because ASU does not give significant pain relief on its own, it’s easy to overlook it as a useful supplement.
◆︎ Why we don’t hear more about ASU due to marketing?
In the early days of marketing ASU, the original factory which produced it signed an exclusive contract with a large US company, which produces human and animal supplements. That company was responsible for advertising their products. Although other manufacturers started producing ASU, it didn’t gain traction, as other new supplements were also hitting the market. Examples of these alternative supplements include resveratrol, quercetin, and CoQ10.
◆︎ How does this apply to the horse?
Early arthritis usually occurs without any symptoms. Because we don’t see symptoms, we don’t see that inflammation within the joint is occurring. We usually start to see symptoms when the arthritis is more advanced. Examples of the advancement are joint space narrowing, erosions of the bone underneath, or pain associated with the deterioration.
A small ASU study with horses was published. In that study, the horses were given a modest dose of ASU, after they created experimentally induced arthritic damage. They found that after 9 weeks, there was no change in lameness. But when they looked at the joint cartilage tissue under the microscope, there was more healing and less damage to the cartilage than the placebo group.
These results are exactly what we would expect. Since it isn’t a strong pain reliever, you wouldn’t expect to see a change in lameness because the pain still exists.
◆︎ Is ASU helpful in other ways for my horse?
Beta-sitosterol has been shown to improve anti-oxidant status, and immune functioning. In other species, the anti-oxidant status improvement has been beneficial to the liver, linings of blood vessels, the intestinal linings, and reproductive system. Additional research has not been conducted in the horse for the ASU product.
◆︎ Should I consider this for my horse?
Knowing that ASU has the ability to support healing of the articular cartilage, it should be considered a useful nutraceutical in our arsenal of support for our arthritic horses.
There are few nutraceuticals known that help the articular cartilage improve on the tissue level. ASU is one of them.
As a reminder, to make the horse more comfortable, it is best paired with a supplement that helps quiet pain signals. Suitable supplements to pair it with include quercetin, turmeric, resveratrol, or Mov-Ease. Other suitable supplements include MSM, ultramicronized PEA, or hyaluronic acid.
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Disclaimer: Statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease or health condition.
©Joan Kulifay, MSc. 2025