ASU (avocado/soybean unsaponifiables) has cell-culture evidence that it enhances glucosamine’s effect on cartilage. Whether it’s worth the premium depends on what’s underneath: ASU pays off when glucosamine is already at the 10,000 mg therapeutic dose, not when it’s compensating for an underdosed base formula.
What ASU actually does
ASU is a concentrated extract from avocado and soybean oils. The “unsaponifiable” fraction is the part that doesn’t convert to soap during processing, and it contains plant sterols and fat-soluble compounds that interact directly with cartilage cells.
The research, primarily from cell-culture studies (Lippiello et al. 2008; Au et al. 2007) and human clinical trials, suggests ASU can inhibit certain cartilage-degrading enzymes, stimulate collagen synthesis by chondrocytes, and strengthen the effects of glucosamine and chondroitin when used together. That “enhancer” role is the key finding. ASU appears to help glucosamine and chondroitin work better than either does alone.
The limitation: controlled dose-response studies in horses are scarce. Most of the ASU evidence comes from human joint research and in vitro work. The 1,000 mg therapeutic threshold used in equine practice is extrapolated from those protocols, not from equine-specific trials. Confidence level: medium.
The real question: ASU vs more glucosamine
This is where most buyers get tripped up. The two ASU-containing products in the equine market are Cosequin ASU ($1.73/day) and Platinum Performance CJ ($6.17/day). Both deliver ASU at or above the 1,000 mg research protocol dose. Both score well on Formula Design because ASU is a non-baseline differentiator.
But both underdose glucosamine relative to the 10,000 mg therapeutic threshold. Cosequin ASU delivers 7,200 mg (72%). Platinum CJ delivers 8,820 mg of a sulfate form, which is effectively less by weight. Meanwhile, SmartFlex Ultra delivers 10,000 mg of glucosamine HCl for $1.84/day with no ASU.
Our scoring reflects this trade-off. SmartFlex Ultra (6.8/10, Recommended) outscores Cosequin ASU (6.5/10, also Recommended) despite having no ASU, because the glucosamine dose advantage (17/20 vs 12/20 on Dosing Adequacy) outweighs the formula breadth advantage (9/15 vs 10/15 on Formula Design). The primary active matters more than the enhancer.
When ASU makes sense
ASU pays off in two situations. First, when a product delivers full-dose glucosamine AND ASU at research-protocol doses. That’s the combination the evidence supports. No product in our current database hits both at a reasonable price, but it’s the theoretically ideal formula. Second, when you’re already feeding a glucosamine-heavy product and want to add ASU as a top-up — standalone ASU supplements exist, though they’re expensive and hard to find in equine-specific formulations.
ASU doesn’t pay off as a substitute for adequate glucosamine. An enhancer can’t enhance what isn’t there. If your supplement’s glucosamine is below 80% of the 10,000 mg threshold, closing that gap will do more for joint health than stacking ASU on top of an underdose.
The practical takeaway
If you’re choosing between ASU and non-ASU products at similar prices, check the glucosamine dose first. If the ASU product’s glucosamine is 80% or more of threshold, the ASU is a worthwhile add. If it’s below 70%, the ASU is being used as a marketing feature, not a therapeutic one. Cosequin ASU sits at 72%, right at the edge. The ASU pushes it into our Recommended tier, but the glucosamine floor is the reason we can still recommend it at all.
Related reading: How much glucosamine does a horse actually need?
Related Questions
Does ASU have any side effects in horses?
No adverse effects have been reported in published equine or human research at standard supplementation doses. ASU is derived from food-grade avocado and soybean oils. The main risk is financial: paying a premium for an ingredient with medium-confidence evidence while the base formula’s glucosamine sits below threshold.
Which Cosequin product should I buy: ASU, Optimized MSM, or ASU Plus?
Within the Cosequin line, ASU is the best option. It shares the same glucosamine, MSM, and chondroitin base as Optimized MSM but adds ASU and boswellia for $0.29/day more. That’s enough to push it from no badge to Recommended in our system. ASU Plus layers HA and green tea extract on top; potentially worth it, but we haven’t audited that product yet.
Can I add a standalone ASU supplement to my current joint product?
In theory, yes. In practice, equine-labelled standalone ASU is rare and typically costs $1.00 or more per day on top of whatever you’re already feeding. For most buyers, switching to a single product that includes ASU (or accepting a product without ASU if the glucosamine dose is already therapeutic) is more cost-effective than stacking supplements.
Sources
- Lippiello L, Nardo JV, Harlan R, Chiou T. Metabolic effects of avocado/soy unsaponifiables on articular chondrocytes. Evid Based Complement Alternat Med. 2008;5(2):191-197. PubMed: 18604248.
- Au RY, Al-Talib TK, Au AY, Phan PV, Frondoza CG. Avocado soybean unsaponifiables (ASU) suppress TNF-α, IL-1β, COX-2, iNOS gene expression, and prostaglandin E2 and nitric oxide production in articular chondrocytes and monocyte/macrophages. Osteoarthritis Cartilage. 2007;15(11):1249-1255. PubMed: 17845860.
- National Research Council. Nutrient Requirements of Horses, 6th Revised Edition. National Academies Press; 2007. Chapter 9 (Nutritional Management of Adult Horses).