Sugar Does Not Cause Equine Metabolic Syndrome

It’s a common belief, however diet does not cause metabolic syndrome.

Eleanor M. Kellon, VMD

Revised 2-4-2022

The wrong diet exacerbates equine metabolic syndrome (EMS) but it doesn’t actually cause it.

It’s easy to see where the idea came from. When a horse/pony/donkey has metabolic syndrome it is very important to limit the sugar and starch in the diet. Starch is digested to glucose before being absorbed. The higher the intake, the higher the animal’s insulin levels will go and the higher the laminitis risk.

However, these abnormal elevations don’t happen with every horse, and evidence continues to grow that metabolic syndrome is genetic.

In 2006, Trieber, et al., published the results of a year-long mixed breed pony herd study following 160 ponies. There were 54 with a previous history of laminitis, and 106 were never laminitic. The diet was pasture for all. There were exaggerated responses to spring pasture in the previously and currently laminitic group only, and this was “consistent with the expected inheritance of a dominant gene or genes with reduced penetrance”.

Genetics as the root cause is entirely consistent with the observation that certain breeds, like Thoroughbreds, Standardbreds, full size Drafts and Warmbloods rarely, if ever, develop EMS unless they also have PPID. On the other hand, ponies, minis, donkeys, Arabians, Morgans and others are at high risk.

A study published in 2016 by Bamford, et al., attempted to induce EMS by making horses obese using a high-fat diet, or high-fat plus high-carbohydrate meal. They succeeded in making them obese, but not making them insulin resistant. In fact, the horses also fed high carbohydrate had better insulin sensitivity than those fed high fat alone. This adaptation to higher simple carbohydrate intake has been reported before in normal horses.

Research work is ongoing to identify the specific genetic components in EMS. The most helpful way to think of reactions to sugar is that it is like a food allergy. The vast majority of people can eat peanuts, but for some it triggers a severe reaction. It’s not that peanuts are inherently dangerous. It’s the individual sensitivity.

It’s actually not all that simple. For example, exercise can protect from elevated insulin reactions even in susceptible horses. The point is though, that sugar and starch are not the villains here. You cannot cause metabolic syndrome by diet. The issue is the individual’s genetics.

For more information to help equines with EMS maintain good health, see



About ECIR Group Inc.

Started in 1999, the ECIR Group is the largest field-trial database for PPID and EMS in the world and provides the latest research, diagnosis, and treatment information, in addition to dietary recommendations for horses with these conditions. Even universities do not and cannot compile and follow long term as many in-depth case histories of PPID/EMS horses as the ECIR Group.

In 2013 the Equine Cushing’s and Insulin Resistance Group Inc., an Arizona nonprofit corporation, was approved as a 501(c)3 public charity. Tax deductible contributions and grants support ongoing research, education, and awareness of Equine Cushing’s Disease/PPID and EMS.

THE MISSION of the ECIR Group Inc. is to improve the welfare of equines with metabolic disorders via a unique interface between basic research and real-life clinical experience. Prevention of laminitis is the ultimate goal. The ECIR Group serves the scientific community, practicing clinicians, and owners by focusing on investigations most likely to quickly, immediately, and significantly benefit the welfare of the horse.



1 Treiber K, Kronfield D, Hess T, Byrd B, Splan R, Staniar WB, Evaluation of genetic and metabolic predispositions and nutritional risk factors for pasture-associated laminitis in ponies. J Am Vet Med Assoc 2006 May 15;228(10):1538-45. doi: 10.2460/javma.228.10.1538.

2 Bamford N, Potter S, Baskerville C, Harris P, Bailey S.Effect of increased adiposity on insulin sensitivity and adipokine concentrations in different equine breeds adapted to cereal-rich or fat-rich meals. Vet J 2016 Aug;214:14-20. doi: 10.1016/j.tvjl.2016.02.002. Epub 2016 Feb 12.

3 Rose L P, Mallicote M, Long M, Brooks S, Metabogenomics reveals four candidate regions involved in the pathophysiology of Equine Metabolic Syndrome. Mol Cell Probes. 2020 Oct; 53: 101620. 



Contact:  Nancy Collins

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