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June 2014



Gastric ulcers commonly occur in many domestic horses, especially those engaged in competitive sports.   According to some researchers up to 90% of racehorses are affected, 42% of top-level three-day eventers, 63% of show jumpers and dressage horses, up to 93% of endurance horses during racing season, 70% of pastured broodmares and 50% of foals. Lesions have been found in one third of leisure horses and some three-quarters of Western pleasure horses.  

(Prevalence of gastric ulcer syndrome in high-level endurance horses. Tamzali Y, Marguet C, Priymenko N, Lyazrhi F.  Equine Vet J. 2011;43:141-144.)


Ulcers are found on the lining of the stomach wall, duodenum and other areas of the digestive tract.   Ulcers are usually caused by unprotected tissues being ‘burned’ by the hydrochloric acid the stomach needs to produce in order to digest food. Ulcers are similar to a painful open skin wound and can be further irritated when in contact with rough food components, the facing stomach wall, and especially, stomach acids and enzymes.     Like a skin wound, gastric ulcers are also subject to secondary infection with opportunistic bacteria  in the stomach.

Gastric ulcers in horses have been associated with eating large volumes of concentrate feeds, physical exertion, gestation, transportation, weaning, and other stresses.  Physical and psychological stress has also been proposed as a suspected cause. 


Horses have evolved to graze almost continuously, their stomachs producing the necessary digestive hydrochloric acid continuously (1.5 litres/hour); in humans it is produced only when food is present. Since the equine stomach empties within 30-60 minutes after a meal, the cells lining the stomach can be exposed to the acids that are secreted for several hours before the next meal.  Horses that are fed only two or three meals a day, with grain or concentrate feeds comprising a large percentage of their diet, are most susceptible to ulcers. Horses that graze continuously or are fed free-choice hay tend to have a lower incidence of ulcers.  Feeding grains may increase levels of the hormone gastrin that stimulates stomach acid production, therefore increasing risk for ulceration.

As less than 10% of equine ulcers heal naturally, management changes and treatment with acid-suppressing drugs are usually recommended by veterinarians for short-term use.  These drugs are effective in providing relief from the pain of gastric ulcers but are generally not expected to produce a permanent cure as the horse does need the hydrochloric acid for digestion.  Acid-suppressing drugs can also disrupt the horse’s digestive system by causing an excessive increase in stomach acid production when the drug is discontinued, thus increasing the risk for additional ulcers.


Alternative to Acid-Suppressing Drugs
Physician Dr Jonathan Wright recommends the use of Chios Mastiha (mastic gum) for the treatment of gastric ulcers and atrophic gastritis.  His book ‘Why Stomach Acid Is Good For You’ is highly recommended.  Atrophic gastritis is a condition where the inner lining of the stomach thins due to chronic inflammation, leading to loss of the cells that secrete hydrochloric acid and digestive enzymes.  Although commonly associated with aging, Dr Wright believes gastric atrophy may also be linked to other causes such as longterm use of the acid-suppressing drugs used to treat gastric ulcers. 


In humans, gastric atrophy is associated with a wide range of disorders including:


  • Poor absorption of minerals, vitamins and amino acids

  • Allergies

  • Skin problems such as dermatitis, eczema and hives

  • Depression

  • Bacterial overgrowth in the gastro-intestinal tract leading to gas, constipation or diarrhea; bacterial infections.

  • Osteoporosis


The high incidence of gastric ulcers in horses is a well-documented, world-wide problem, but it is currently unknown if atrophic gastritis could also be an issue for horses. 


It is thought that Chios Mastiha may provide a safe, inexpensive, alternative remedy for horses experiencing digestive problems.   As with the use of Mastiha for humans, it is anticipated that horses will benefit from a short course and will not need to consume Mastiha on a permanent basis.

What is Mastiha used for?
The aromatic, pine-like flavour of Chios Mastiha has been valued for thousands of years in food preparation, especially festive fare.    It has also been famous for its ability to safely relieve a wide range of digestive disorders from bad breath to peptic ulcers, and was even the preferred treatment for cholera; it was thought to be the world’s first natural chewing gum.   It is currently used in a wide variety of food applications as well as skin-care lotions and toothpaste, and numerous medicinal remedies.


Extensive research has been conducted on Chios Mastiha in more recent years establishing that it has broad-spectrum antimicrobial properties, and is effective against disease-causing yeasts and fungi, including candida albicans.  It has also been found to provide protection against gastro-intestinal damage from drugs such as aspirin and phenylbutazone.


A 1985 study by the University of Thessalonika discovered that Mastiha can reduce bacterial plaque in the mouth by 41.5%.  


A 1998 study by the University of Athens found that Mastiha resin oil has both antibacterial and antifungal properties.


A 1998 study by Nottingham University, published in the New England Journal of Medicine, found that Mastiha heals pectic ulcers, and is specifically effective against several strains of the ulcer-causing bacterium helicobacter pylori. (Mastic Gum Kills Helicobacter pylori N Engl J Med 1998; 339:1946).  


What is Chios Mastiha Gum Resin?
Mastiha gum is a resinous sap that exudes from the shrubby mastic tree (Pistacia Lentiscus, var. Chia) found only in the southern part of the  Mediterranean island of Chios. The annual harvest for each tree yields only around 180g of Mastiha gum. Mastic trees transplanted to other regions of the island, or grown in other countries, do not have the therapeutic qualities of trees grown in the south of the island.

The clear drops of sap change to an opaque pale yellow colour as they dry naturally in sunlight.  


After harvesting, drying and cleaning, some Mastiha crystals are ground into a fine powder. Nothing is added to Mastiha gum, the end product is completely pure.

Mastiha tear

Mastiha crystals

Mastiha powder


The Pistacia Lentiscus, var. Chia, tree should not be confused with the common Pistacia Lentiscus that grows prolifically all over the Mediterranean region.  Oils produced from the leaves of the common Pistacia Lentiscus contain toxic tannins that should not be consumed.

Other studies have found Mastiha to be effective against duodenal ulcers, verified by endoscopy (Al-Habbal M J, A-Habbal Z, Huwez F U. Clin Exp Pharmacol Physiol. 1984 A double-blind controlled clinical trial of mastic and placebo in the treatment of duodenal ulcer).

Has Mastiha been used for horses?

Reports from around the world indicate the therapeutic benefits seen in humans are also replicated in horses.   It has been used successfully for horses with gastric ulcers where conventional drug treatments have not been effective or longlasting. As only a small proportion of the bacterial population of the horse’s gut has been isolated and identified, it is possible the antimicrobial and antifungal properties of Chios Mastiha are acting in ways that have yet to be discovered and understood. Informal trials have recently commenced in Australia, with early results being far beyond expectations, even in horses where no obvious health problems were evident.


Numerous horse owners state they have difficulty getting their horses to eat sufficient calories to maintain weight or energy.   The problem is compounded when attempting to feed anything that is likely to irritate inflamed or ulcerated tissues, such as salt or magnesium chloride, even though the horse may be displaying signs of deficiency.   This is a common problem with racehorses and other performance horses.


The observations, summarized below, from owners who have given their horses Chios Mastiha indicate a consistent pattern is starting to emerge between three and twenty-one days after commencement of the remedy:


  • Increased appetite and enthusiasm for eating any feed presented, in horses who had previously wasted feed or taken hours to consume a small hard-feed regardless of salt content.


  • No longer reluctant to consume feeds containing salt and/or magnesium chloride.


  • Several horses with longterm, diagnosed gastric ulcers have improved rapidly with no other alteration to feed or manangement, including one racehorse with a grade 3 ulcer that had not responded to conventional treatment.  


  • Drastically reduced need for magnesium.  One horse that had for years consistently needed 9.7g of elemental magnesium per day from supplements, dropped to 3.4g per day after only 3 weeks of being given Chios Mastiha (with no other changes to diet or living conditions).  This reduced need has been maintained for several months after completing the initial 4-week course despite increasing NSC levels in pasture grasses.   There were no previous indications of gastric ulcers in this horse.


  • Visible increase in coat quality and shine, even in horses still shedding their winter coats.


  • Relaxed temperament and the emergence of gentle ‘playfulness’ in horses not usually known for being playful.


  • Change in body shape to a completely relaxed posture; horses not in work look as though they have suddenly acquired full, soft, developed muscles.



How is Chios Mastiha given to horses?
Using the protocol for people as a model, it is recommended that one level teaspoon (3g) of Mastiha (either powder or crystals) be mixed with a tiny amount of something that is tasty to a horse, and then fed separately 10 to 15 minutes before a meal, thus allowing time for the active elements in the resin to work on the horse’s stomach before the arrival of a meal.   A tablespoon of dry copra and a teaspoon of black sunflower seeds works well; start with a pinch of Mastiha and work up to the teaspoonful over a few days to allow time for the horse to adjust to the new flavor.   Most horses come to accept the flavor quickly, some even happily taking it alone after a few days.   If all else fails, the Mastiha powder can be mixed into apple puree or yogurt and then syringed over the tongue.


At this stage it is suggested that one level teaspoon (3g) of Chios Mastiha be fed once per day as above, for four weeks only. It is not yet known if this once-only remedy will be sufficient for all horses, especially those with diagnosed gastric ulcers.   As more reports are received from horse-owners, this article will be updated with further information.



Go to the SUPPLIERS page for information about where to buy Chios Mastiha Gum Resin in your country

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