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Leaky Gut Syndrome; Health & Soundness

The ‘gut’.  Homebase to the immune system, source of digestion, and nutrient assimilation for the horse. We all know how an upset or disagreeing stomach can drain us of our energy, vitality, and overall zeal for certain functions, but did you know that the gut may actually be involved with many clinical diseases in the horse and even impact the joint, soundness, and allergies?  It’s true and something we have lightly investigated in a clinical study with horses.  The connections have been known for a long time in human research data and there are indications in the equine industry as well, but all to often, we fail to recognize the problem or address it properly.Leaky gut syndrome is a clinical term passed around in the human medical world for quite some time. In fact, many may be familiar with the terminology and even what it refers to.  It is a complicated process and one that we certainly do not fully understand, but nonetheless, it is interesting.  Possible connections with many clinical problems ranging from joint disease, allergies, fatigue, fibromyalgia, IBD, Crohn’s, IBS, diabetes, COPD, immune conditions, cancer and many, many more are real.  Two questions really remain to be answered; is the condition a cause or effect, and how do we best manage it?

Leaky Gut and Influence on Horse Health

Diagram of Leaky Gut Syndrome in the Horse
Diagram of Leaky Gut Syndrome in the Horse

For the longest time, as a veterinarian, I have divided our equine patients into one of two categories, no matter the condition.  Either they were an easy keeper or non-easy keeper.  The reason that I have done this is that I have always felt there was a tie in between their inflammatory problems and the gut.  This doesn’t always happen with each horse, but if we look for subtle clues, the connection becomes real. Obvious clues would be diarrhea, loose stools and repeat colics, but there are more subtle clues such as overweight body condition, poor hair coat, poor hoof conditioning and even poor tendon health.  In these situations, we have to remember that the gut is responsible for nutrient digestion and assimilation, in which case if there is a problem in this area, then maybe it might be reflected in a poor hair coat or hoof condition.  The tendons are viewed the same, often succumbing to injury as a result of poor tissue strength secondary to poor nutrient assimilation.

Another term for leaky gut syndrome is intestinal hyperpermeability, which is more reflective of truly what is going on.  In order to understand the process and find solutions, we have to first understand what is truly going on.

On a basic level, the gastrointestinal tract is home base for the immune response.  All cells tend to communicate via cytokines, which are inflammatory proteins and essentially cell signalers, almost like calling a friend on a cell phone.  They talk to one another and when they react in one area, that reaction can trigger a reaction in another part of the body.  The other element we need to understand is that the intestinal wall is meant to serve as a barrier, allowing certain things like nutrients to be absorbed, while keeping other things like bacteria where they should be.  This is designed to be a contained system.

In leaky gut syndrome, the intestinal barrier is broken down and become more permeable or ‘leaky’. When this happens, bacteria can then access the general circulation as can inflammatory products, dyes, additives, coloring agents, preservatives and many other chemicals that may be found in the diet.  As these agents enter the general circulation, they can trigger a host of reactions and impact cellular health and integrity.  As often is the case, the immune system reacts to these agents, viewing them as ‘foreign invaders’, which mounts an inflammatory response on a certain level.  Through cellular signaling, the local immune response can create a systemic response.  As this condition continues to develop, it may become more severe, resulting in higher levels of inflammation throughout the body, immune dysfunction and decreased ability of the gut to do its job, which is absorb nutrients and digest food properly.

In human medicine, there has been much research done connecting ‘leaky gut syndrome’ and conditions including diabetes, allergies, COPD and even cancer.  In equine medicine, the condition has been noted in cases of severe colic, diarrhea, hindgut problems and cases of colitis.

Is Leaky Gut a Cause or is it the End Result of Something Else?

Leaky gut syndrome has been researched for quite some time, but what we don’t know is whether if the condition occurs as a result of some other health problem or if it is a primary problem that leads to other conditions?  What we do know is that leaky gut syndrome can significantly contribute to a heightened level of inflammation throughout the body, but again, we don’t know if it is primary or secondary player in the game.  It is complex and there are many factors that can contribute to the development.

In humans, leaky gut syndrome is a common problem secondary to chemotherapy or radiation.  In those patients, often there is associated weight loss, diarrhea and even severe bacterial infections secondary to bacterial translocation.

In horses with severe colic, where a piece of bowel is compromised, we also have leaky gut syndrome, in which bacterial and other inflammatory factors reach the general circulation and contribute to major health problems.

A scenario that most horse owners are familiar with is laminitis secondary to pasture exposure or excess carbohydrate intake.  Automatically, we assume it is the carbs that are to blame and we are correct to a degree, but there is more to the story.

In all animals and people, there is a perceived normal balance of bacteria within the gut.  Each bacteria has a job and assists in food breakdown and fermentation, helping us to get the most from our food in regards to nutrients.  One interesting group of bacteria is referred to as lactic acid producers and includes lactobacillus, enterococcus and some staphylococcus organisms.  These bacteria tend to thrive on carbohydrates such as starch and fructans, which when present, allow them to increase in number.  Under normal circumstances, this group of bacteria represent a small percentage of the overall bacterial population.  In the case of excess carbohydrate intake, the small intestine can only absorb so much and the remaining amounts go the colon where these lactic acid bacteria then ferment the sugars.  Again, if excess sugars are present for long periods of time, the population can change dramatically and with it, the environment within the bowel will change.

One of the first changes is a alteration in the pH of the environment, usually one towards acidic.  As the pH changes towards acidity, then normal ‘good’ bacteria cannot thrive and begin to die off. As the population of the ‘bad’ bacteria flourish, the immune system often reacts locally, releasing various inflammatory mediators into the local environment.  Over time, with continued progression, these events can then lead to a break down in the gut barrier, creating the leaky gut phenomenon.

Now, this is a simple scenario based on excess carbohydrate intake in a horse, but the model is real, but the question is “primary or secondary”?

In the case of laminitis secondary to pasture exposure, the laminitis is generally perceived to be secondary to the gut changes that have occurred, as the gut changes can occur fairly quickly and then are potentially thought to contribute to the laminitis.  Again, all of this is tied into the process of unregulated inflammation, which then on a different level contributes to laminitis.

In humans, the leaky gut phenomenon has been connected or found in cases of allergies, diabetes and COPD.  They know many of these patients demonstrate leaky gut syndrome, but the question is whether if it is a primary event or secondary?  Often, if a person’s leaky gut problems are improved, the primary disease still remains but appears to be more controlled.  Does this mean that it is secondary??  Not necessarily as we have to remember that there are many levels of unregulated inflammation and over time, the damage can appear at many levels and to different degrees.  Even if we improve the leaky gut syndrome, the damage may be more permanent at a distant site or take more time to resolve.

Potential Contributors to Leaky Gut Syndrome in the Horse

Excess carbohydrate intake is one primary factors connected with leaky gut syndrome, with a secondary shift in the bacterial population.  Are there other causes?  The answer is yes as there are many.  Stress and processed feeds/food are also known culprits, as may be genetics.

Stress is a huge player in gastrointestinal problems in the horse, pet and humans.  We all know what happens to our gut when we are overly stressed or nervous.  Sometimes it is not so pleasant, but the connection is real.  Stress results in neurological changes to the gastrointestinal tract and also results in the over production of cortisol, which has it’s direct impact on inflammation and health.

Processed foods have also been the subject of some research papers, focusing on what is termed ‘advanced glycation end products’ or AGE’s, which are byproducts of certain sugars. In some foods, due to processing and handling, the AGE potential is markedly increased due to heat application or even through other additives placed within the food.  Even with cooking of foods, we have a different range of AGE’s dependent on the handling.  Frying and broiling tend to produce higher levels of AGE’s, while roasting and boiling tend to produce less.  The implications in the equine world are yet to be determined.  The overall problem is that AGE’s in high levels, tend to elicit and inflammatory response within the gut and may contribute to leaky gut syndrome and even systemic inflammatory problems.

Other factors to consider when discussing processed foods is the high use of additives, coloring agents, preservatives and even artificial sweeteners…all of which may be contributors.

Therapies and Future Learning On Leaky Gut and Digestive Health in the Horse

There are many therapy options that may assist in the healing of the gut and therefore help to restore health.  What we don’t know is when to apply these options?  Do we apply them by themselves or together with others to get the best result.  Also, what dose is needed and for what situation?  Is it possible to determine if leaky gut syndrome is present before clinical problems develop?

We have much to learn and in part two of this article, we will discuss our ‘fecal research project‘, what we have learned thus far and therapy options that may be worthwhile pursuing.

For further information on the diet and influence on gut health in the horse, click this article.


All my best,

Tom Schell, D.V.M.

Nouvelle Research, Inc.





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