Sodium hyaluronate (HA) is a substance that occurs naturally within the joint and helps to create a cushion between bones and tissues. It’s been used successfully to treat the symptoms of arthritis in horses when injected into the joint, where it acts as a lubricant and mild anti-inflammatory.

HA is also used as an IV treatment for arthritis (Legend is the best known). When given in this way it attaches to anti-inflammatory receptors on the blood side of the joint capsule and has very strong systemic anti-inflammatory properties, but no lubricating effect.

So what about oral HA? It’s one of the most talked about ingredients in oral supplements and it is available in powdered, gel and liquid forms. It is expensive. But does it work?

It depends on who and what you believe. And also what you think it does.

When I asked my vet about it, his opinion was that oral HA is not absorbed orally. But there are a lot of people who believe strongly that it’s making a difference for their horses.

Let’s look first at the gel vs. powder or paste.

Here’s what’s written on the website for Hyaluronex, a popular HA product:

Hyaluronan must be completely hydrated to be bioavailable and absorbed.² Further, once absorbed it must have the appropriate molecular characteristics including molecular weight to be effective.³

Hyaluronan is among natures most water-loving molecules. As a powder or pellet it slowly absorbs up to 1000 times its’ weight in water creating a thick, viscous fluid. In healthy mammals the transit time from ingestion to excretion does not provide the necessary time for hydration of this incredibly hydrophilic molecule. Research indicates that little of the High-Molecular-Weight dry forms are absorbed before excretion and that while some Low-Molecular-Weight dry forms may be hydrated and absorbed during ingestion and digestion they are not effective.³

There is also debate over whether oral dosing (squirting it into the horse’s mouth, or under its tongue) increases the efficacy compared to top dressing. The theory here is that it is more readily absorbed through mucous membranes and that if it’s top dressed it gets at least partially digested before it gets to the mucus membranes.

There is also no evidence that HA delivered orally has any direct effect on the joints, despite the claims. For example, On the Lubrisyn website, they claim that,

Lubrisyn’s purified, high molecular weight HA is rapidly and thoroughly absorbed by the body and is ideal for increasing the viscosity of the synovial fluid that cushions and protects the joints.

However, on the FAQs page, there is a statement from Lubrisyn website that states:

There have been no studies completed to date that show increases of HA in the joints after administration of an HA supplement. These types of studies are extremely invasive to the joints as well as difficult on the animal. There are existing studies that show marked improvement in animals’ mobility and performance while undergoing HA supplementation.

I did find reference to one study, conducted in the Czech republic that finds that horses given a gel-based oral HA did show results, Medicinal properties in whole foods:

Researchers in the Czech Republic have performed a number of studies on sodium hyaluronate in horses, rats and humans. The most extensive animal experience to date with hyaluronan has been with racehorses. For example,

In a study of 53 sport horses of various breeds, given oral sodium hyaluronate syrup 100mg/500kg body weight for 30 days, good to very good results were observed in multiple orthopedic diagnoses. (4)

• Daily 100 mg doses of an oral hyaluronan gel produced higher serum levels at day 7 in 4 horses than a single IV infusion of hyaluronan in 4 comparable horses. (5)
• The effect of 100 mg of hyaluronan as an oral gel on lameness and other orthopedic conditions in 13 actively training Thoroughbreds was notably beneficial when compared with 12 others horses serving as controls. (6)
• A blinded study of 13 horses found a significant benefit of 20 mg hyaluronan, 5000 mg of glucosamine sulfate and 450 mg of chondroitin sulfate in accelerating recovery from arthroscopic surgery. (6)
• Four Thoroughbreds with synovitis of the MCP joints were cured or considerably improved after 21 days of 100 mg of hyaluronan as an oral gel. Improvement was noted during the first week. (6)
• A review of various available veterinary preparations of hyaluronan rated their effectiveness. The nutraceutical preparation was found to be noticeably effective. A commercial preparation of hyaluronan oral gel was deemed to be as effective as an IV formulation. Finally, intra-articular injections were rated high for severe disease, when accompanied by maintenance on nutraceutical preparations. (7)

Studies like this, plus the many users who report that their horses show improvement after taking an oral HA product lead me to believe that there is a positive effect that is imparted from oral HA products. In my reading for this article, my guess (and it is truly a guess) is that it works largely the same as the IV treatment: it reduces inflammation. I just can’t figure out how a feed through HA supplement can actually improve the synovial fluid in the joint. Perhaps for many horses, a system reduction in inflammation is enough. Or, as a vet that I’ve worked with said, “if you think it’s working, it probably is. But don’t hold your breath for research because it’s too expensive to conduct.”