Some beliefs simply will not die, no matter how incorrect they are.
Horses, ponies, donkeys/mules and minis which are prone to high insulin levels are at risk of developing health problems. For example, it has been clearly demonstrated that high insulin may trigger laminitis and is the cause of around 90% of cases. To keep insulin controlled, a key step is to limit those things in the diet that trigger insulin release.
The AAEP’s Laminitis Working Group did a four year study with the goal of identifying laminitis risks. Other than diet, EMS pattern obesity, known EMS or PPID and use of corticosteroids within 30 days were identified. All relate to equine metabolic syndrome [EMS] and elevated insulin.
A 2006 field study performed by a group from Virginia Polytechnic followed a herd of 106 mixed breed ponies on pasture for a year, performing pasture analyses and monitoring the ponies using proxies of insulin resistance they had developed from the results of intravenous testing. They found both prior laminitis and development of acute laminitis correlated well with indicators of insulin resistance. There was no increase of fructan in the pasture when laminitis cases appeared, no indication of diarrhea or hind gut upset.
In a 2016 study, Menzies-Gow at al followed 446 animals on pasture over a period of 3 years. They found the most reliable indicator of risk of laminitis was basal insulin levels. Also significant were low adiponectin and high insulin response to dexamethasone. Fructan does not increase insulin. There was no indication of the diarrhea or hind gut upset that accompany fructan overload.
A 2019 study by de Laat et al looked at 301 cases of naturally occurring laminitis and found EMS and/or PPID in 94%. They were also careful to point out those that did not have elevated insulin at time of testing may have been reflecting their current diet rather than their state at the time of acute laminitis. No diarrhea or other indication of hind gut distress was reported.
There are many other studies and they all come back to insulin. Very large doses (over 8 lbs for a 500 kg horse) of pure fructan by stomach tube, a highly unnatural scenario, can experimentally cause laminitis by resulting in extreme hind gut acidity, damage to the intestinal lining and absorption of bacterial products in the same way gorging on grain can. This hind gut upset is accompanied by diarrhea, septicemia and fever. These horses are clearly sick. None of that happens with naturally occurring laminitis.
Not only are there zero documented cases of high fructan in pasture causing laminitis, the levels of fructan naturally found in a whole day’s worth of eating pasture grasses almost never come even close to the amount needed to cause laminitis. Could laminitis prone horses be more sensitive to fructan?
Nope. Borer et al 2012 found virtually no insulin response to fructan in ponies whether they had a past history of laminitis or not. Crawford et al 2007 fed a moderate fructan dose to normal and laminitis prone ponies and looked at the changes in fecal pH and fermentation products. They found that pH and fermentation products did change but none of that was reflected in blood levels so wasn’t absorbed. There was also no difference in documented changes between normal and laminitis prone ponies.
Only simple sugars (ESC fraction on analysis) and starch can increase insulin. Those two things should be less than 10% combined [ESC + Starch less than 10%] for at risk horses. You may see fructan described as a sugar. It is not a sugar. It’s a complex carbohydrate that cannot be digested by the horses enzymes – like fiber. NSC, nonstructural carbohydrates, equals ESC + starch + fructan. The fructan is irrelevant and using NSC can lead to people overlooking hays that are safe.
The greatest danger in perpetuating the fructan myth is that owners will rely on supplements designed to control pH or alter hind gut fermentation to protect their horse or pony from laminitis. They won’t help if your animal is in the high risk group with endocrine disease, which accounts for 94+% of laminitis cases.
There are no magic bullet supplements to protect from laminitis. Only an appropriate basic diet can help. For a good review of the most current science see Patterson-Kane et al. You won’t find fructan mentioned even once.
Eleanor Kellon, VMD