Forget About Fructan and NSC

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.

Insulin rises because of sugar and starch, not fructan

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

About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions,, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition.
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7 Responses to Forget About Fructan and NSC

  1. Jennie Hill says:

    I am confused. My pony has IR and is on Metformin. I have had his hay analyzed and it is safe (ESC less than 10 percent). I have also switched him to Stabul 1 feed. He was diagnosed with IR when acute laminitis occurred 3 months ago. Since then, I have put boots on him and turn him out only during the day. Then, take the boots off and stall at night. NO GRASS. However, unless I am not reading your article correctly, is he ok to eat grass? I have tried to kill it, actually. So, there is a sparse amount. I have had him on a dry lot for the last 3 months. Of course, now that spring is almost here, I see clumps of fresh, green grass trying to grow. Is this safe for him or not? Does the Metformin help? I take him on daily walks and try to exercise him as much as he can tolerate with the boots on. I’ll admit it; I am paranoid about allowing him to graze at all! Please advise. Thank you so much!! Your website has been invaluable!!!

    • Dr. Kellon says:

      No, grass is not OK. Grass has variable amounts of sugar and starch depending on type and the growing conditions. It is usually most dangerous in the spring. Metformin can’t guarantee grass safety.

      • Jennie Hill says:

        My vet. says the grass is not the problem; it is his IR. This is so frustrating. So, can he ever eat grass, even if it’s mowed down and perhaps on a cloudy day or for short periods? I don’t want to put him at risk, of course. What about diet, exercise? Can this help to support the insulin regulation? I just want to do what’s best for my pony. Thank you so much!

  2. Jessica Ellis says:

    Hi dr Kellon I have just read your latest post about fructan in grass not being a cause for laminitis rather starch and simple sugars, which makes a lot of sense. It was quite timely for me actually as I have been looking at reseeding a couple of my horse paddocks that have a lot of ryegrass and is creating a weight management issue for my herd and was considering a native seed mix targeted at horses and advertised as laminitis safe. I’ll pop the link to the website in below because I am now reconsidering if it is in-fact a safe option, as the information they provide is completely opposite with no data to back up their claims, I would love to get your opinion, although based on the information you provide from actual scientific research (which as a research scientist I wholeheartedly love to see) I’m thinking not.

    Thanks for your time Jessica

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    • Dr. Kellon says:

      The explanation in that article is incorrect. Cool season grasses store fructan, not simple sugars. It is primarily stored in the base. There is still a problem with “improved” grasses because high fructan goes hand in hand with higher sugars. However, as in animals, sugar is essential to the plant’s life. Sugar levels in pastures are affected by many factors. Even native grasses may reach levels high enough to induce laminitis in susceptible horses. The key word here is susceptible. Unless the horse has EMS with high insulin responses it won’t be susceptible to laminitis.

  3. Margareta Andersson says:

    I was wondering if you have read this article, Fructokinase, Fructans, Intestinal Permeability, and Metabolic Syndrome: An Equine Connection?:
    It may explain why some horses (my mustang/morgan mare for instance) needs to have low (5%) ESC hay soaked when WSC is 11%

    • Dr. Kellon says:

      I’ve read it and it’s pure speculation. The microflora doesn’t liberate fructose, it utilizes it. Fructose itself causes minimal insulin reaction anyway. It causes problems by inducing a fatty liver, which is rare in full size horses. If they actually come up with any solid evidence I’ll gladly change my mind.

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