Researchers tested whether a supplement made from plant compounds called polyphenols could help horses with asthma breathe easier. They gave the supplement to 18 horses—some healthy and some with asthma—for 6-8 weeks. The horses with asthma showed improvements in their lung inflammation markers and breathing patterns. In a second test with 10 asthmatic horses, those receiving the supplement had lower breathing rates and fewer abnormal breathing sounds when exposed to dusty hay. While these results are promising, the study was small and only tested horses, so more research is needed before we know if this could help other animals or humans.

The Quick Take

  • What they studied: Whether a supplement made from plant compounds could reduce inflammation in the lungs of horses with asthma and help them breathe better
  • Who participated: 28 horses total: 18 in the first part of the study (8 healthy, 10 with asthma) and 10 asthmatic horses in the second part. The horses were given the supplement daily for 4-8 weeks
  • Key finding: Horses with asthma that received the plant compound supplement showed less inflammation in their lungs and lower breathing rates compared to horses that didn’t receive it. The improvement was especially noticeable when horses were exposed to dusty hay, which normally makes asthma worse
  • What it means for you: This research suggests that plant-based supplements might help manage asthma symptoms in horses, but only when combined with other treatments like keeping the environment clean and dust-free. This is early-stage research, so horse owners should talk to their veterinarian before trying this approach

The Research Details

The researchers conducted two separate experiments. In the first part, they gave 18 horses (8 healthy and 10 with asthma) a daily supplement containing polyphenols—natural compounds found in plants—for 6 to 8 weeks. Before and after the supplement period, they collected samples from the horses’ lungs using a special procedure called bronchoalveolar lavage (basically rinsing the lungs to collect fluid for testing) and took blood samples to measure inflammation markers.

In the second part, they took 10 horses with asthma and split them into two groups: one group received the supplement along with a low-dust diet, while the other group only got the low-dust diet without the supplement. After 4 weeks, they deliberately exposed both groups to dusty hay for another 4 weeks to see how well the supplement protected the horses’ lungs. They measured breathing rates, listened for abnormal breathing sounds, and checked inflammation levels.

This approach allowed researchers to test both whether the supplement works on its own and whether it helps when combined with environmental changes like reducing dust.

Testing supplements in horses with asthma is important because horses naturally develop asthma-like diseases similar to humans, making them good models for understanding how treatments might work. By measuring both inflammation markers in the lungs and actual breathing improvements, the researchers could see if the supplement worked at the cellular level and in real-world breathing performance. The second part of the study was especially valuable because it tested the supplement under challenging conditions (dusty hay), which is when asthma symptoms typically get worse.

This study has both strengths and limitations. Strengths include measuring inflammation in multiple ways (blood tests and lung fluid samples) and testing the supplement under conditions that naturally trigger asthma symptoms. The study also included a control group in the second part, which helps show that improvements were due to the supplement rather than other factors. However, the sample size was small (only 28 horses total), and the study was conducted only in horses, so results may not apply to other animals or humans. The researchers didn’t mention whether they used blinding (where researchers don’t know which horses got the supplement), which could affect results.

What the Results Show

In the first part of the study, horses with asthma showed significant improvements after receiving the polyphenol supplement. Specifically, the percentage of immune cells called neutrophils in their lung fluid decreased, and levels of a protein called IL-6 (which causes inflammation) dropped significantly. Interestingly, another protein called IL-10 (which actually reduces inflammation) decreased more in asthmatic horses than in healthy horses, suggesting the supplement was changing how their immune systems responded.

In the second part of the study, the differences between supplemented and non-supplemented horses became even clearer when they were exposed to dusty hay. Horses receiving the supplement had significantly fewer abnormal breathing sounds during a special breathing test called a rebreathing exam. They also had lower breathing rates overall—about 8-18 breaths per minute lower than horses without the supplement. These are meaningful improvements because lower breathing rates and fewer abnormal sounds indicate easier, more comfortable breathing.

The improvements suggest that the polyphenol supplement may work by calming down the inflammatory response in the lungs, making it easier for asthmatic horses to breathe, especially in challenging conditions.

While not the main focus, the study also showed that healthy horses receiving the supplement didn’t show the same dramatic improvements as asthmatic horses, suggesting the supplement may work specifically by helping the overactive immune systems of asthmatic horses return to normal. This is actually a positive finding because it means the supplement appears to target the problem rather than just suppressing all immune function. The fact that improvements were most noticeable when horses were exposed to dusty hay (a known trigger) also suggests the supplement provides real-world benefits in situations where asthma symptoms naturally worsen.

This research builds on earlier studies showing that polyphenols—plant compounds found in foods like berries, grapes, and tea—have anti-inflammatory effects in human asthma patients. However, this appears to be the first study testing these compounds in horses with asthma. The findings align with what scientists expected based on human research, which is encouraging. The study adds to growing evidence that natural plant compounds might help manage inflammatory diseases, though more research is needed to understand exactly how they work and whether they’re effective in other species.

Several important limitations should be considered. First, the study involved only 28 horses, which is a relatively small number, so results might not apply to all horses with asthma. Second, the study was conducted only in horses, so we can’t assume these results would work the same way in humans or other animals. Third, the researchers didn’t clearly describe whether they used blinding (keeping researchers unaware of which horses got the supplement), which could introduce bias. Fourth, the supplement was only tested for 4-8 weeks, so we don’t know if benefits continue over longer periods or if horses develop tolerance to it. Finally, the study didn’t compare the polyphenol supplement to other existing asthma treatments, so we don’t know how it compares to standard veterinary care.

The Bottom Line

Based on this research, polyphenol supplementation appears promising for horses with mild asthma when combined with environmental management (like reducing dust and improving air quality). However, this is early-stage research, so the evidence is moderate rather than strong. Horse owners should not use this as a replacement for veterinary care or standard asthma treatments. Instead, discuss with your veterinarian whether adding a polyphenol supplement might complement your horse’s current asthma management plan. The supplement appears most beneficial when combined with other dust-reduction strategies.

This research is most relevant to horse owners whose horses have been diagnosed with Equine Asthma Syndrome, particularly those with mild to moderate symptoms. It may be especially interesting for owners looking for additional ways to manage asthma alongside environmental improvements. Veterinarians treating equine asthma should be aware of this emerging research. However, this research doesn’t yet apply to humans with asthma, dogs, cats, or other animals, though it may inspire future research in these areas. People with asthma should not assume these results apply to them without further human studies.

Based on this study, improvements in breathing and inflammation markers appeared within 4-8 weeks of starting the supplement. However, the most noticeable improvements occurred when horses were challenged with dusty conditions, suggesting the supplement may take several weeks to build up in the system before showing clear benefits. Realistic expectations would be to see gradual improvements over 4-8 weeks, with the most dramatic benefits appearing when asthma triggers (like dust exposure) occur. Long-term benefits beyond 8 weeks are unknown and would require additional research.

Want to Apply This Research?

  • Track your horse’s breathing rate daily (count breaths per minute at rest) and note any respiratory sounds during exercise or when exposed to dust. Record these measurements weekly to monitor trends. Also track environmental dust levels and any visible respiratory symptoms like coughing or nasal discharge.
  • If your veterinarian approves, start a polyphenol supplement alongside dust-reduction measures (improved ventilation, dust-free hay, reduced bedding dust). Use the app to set daily reminders for supplement administration and to log environmental changes you make to reduce dust exposure.
  • Create a long-term tracking system that monitors breathing rate, respiratory symptoms, and environmental factors weekly. Compare measurements from high-dust periods versus low-dust periods to see if the supplement provides additional protection. Share this data with your veterinarian at regular check-ups to assess whether the supplement is providing meaningful benefits for your horse’s specific situation.

This research was conducted in horses and represents early-stage findings. Polyphenol supplementation should not replace standard veterinary care or prescribed asthma treatments for horses. Always consult with your veterinarian before starting any new supplement, as individual horses may respond differently and supplements may interact with other medications. This article is for informational purposes only and does not constitute medical advice. The study involved a small sample size and longer-term safety and effectiveness data are not yet available. Results in horses may not apply to other species, including humans.