Sugar, fructan, obesity and lifestyle diseases – what do we really know?

⚠️ In short: This is why you should be careful about sugar and fructan in grass

Grass can be a hidden danger – especially for frugal horses and ponies. Sugar increases insulin levels and can lead to laminitis in sensitive horses. Fructan disrupts the gut and can trigger inflammation. Both are most dangerous in spring and autumn , on cold mornings and when grass is stressed .

Even fertilized grass with low fructan content can produce a high insulin response.

👉 Therefore: Feed with care, limit the amount and time on grass – especially for horses in the risk group – and look at the horse's entire metabolism.

🧩 Sugar, fructan, obesity and lifestyle diseases – what do we really know?

Many horse owners have heard it before:
“Be careful with the grass – it can cause lameness.”

But what is it really about? Why is grass to blame – and what do sugar, fructan, insulin, inflammation and metabolism have to do with it?

Here you get a comprehensive overview - in language that makes sense and backed by the latest knowledge.

🍬 What is sugar – and why can it be a problem?

Grass forms sugar via photosynthesis, where CO₂ from the air and water from the soil are converted in the green parts of the plant (chlorophyll) into different types of sugar:

• Glucose – used directly as energy

• Fructose – is formed from glucose and can be linked together in chains as fructan

• Sucrose – occurs when glucose and fructose are bound together; it is the plant's transport sugar

When a horse eats grass with a high sugar content, it can cause a rapid increase in blood sugar and therefore insulin . In insulin-resistant horses (such as those with EMS or PPID), it can lead to hyperinsulinemia – a condition in which insulin production becomes abnormally high. This is one of the primary causes of lameness.

Insulin is a storage hormone that promotes fat accumulation and can contribute to inflammation when levels are chronically elevated.

💡 Although fructose does not stimulate insulin to any significant extent , it is part of the grass's overall sugar profile - and can thus indirectly burden the metabolism of sensitive horses.

🌾 What is fructan – and why is it different?

Fructan is a type of storage sugar that grasses build up in chains of fructose. It occurs especially in grasses from temperate climates – e.g. ryegrass, timothy and meadow fescue – and is formed especially in these situations:

• In spring and autumn

• After cold nights

• In case of drought, stress or overgrazing

• Late in the day, after a lot of sunlight

Fructan is not digested in the small intestine, but reaches the hindgut , where it is fermented by bacteria. This can cause:

• Acid shift in the intestine

• Disturbances in the bacterial flora

• Release of toxins and inflammatory substances (e.g. endotoxins = toxins from bacteria)

In sensitive horses, it can lead to colic or lameness – even without a metabolic disease.

🧪 Fertilizer – less fructan, but higher insulin response?

When talking about grass and the risk of lameness, it is important to understand that fertilizer changes the nutrient content of the grass :

• Fertilized grass often has lower fructan content , because the plant prioritizes protein

• It has a higher protein content , which is an advantage for many horses.

• But it can cause a stronger insulin response – especially in sensitive horses.

💡 Fertilized grass can provide lower fructan load - but still be problematic for horses with insulin resistance.

🔍 Sugar vs. fructan in the horse's metabolism

📊 What do the analyses say?

Roughage analyses show:

• NSC (non-structural carbohydrates) = sugar + starch + fructan

• ESC (ethanol-soluble carbohydrates) = free sugars, without fructan and starch

The values ​​vary depending on grass type, growing conditions and harvest time.

⚠️ Fructan and sugar – a dangerous cocktail

Many horses – especially frugal breeds and ponies – have hidden insulin resistance. Grasses high in sugar and fructan can trigger serious reactions.

Research shows:

• Afternoon grass gives higher insulin response than morning grass

• Horses can develop lameness without classic symptoms , simply due to insulin imbalance.

🧬 What is EMS?

Equine Metabolic Syndrome (EMS) is a metabolic disease in which the horse has difficulty regulating insulin. It is often seen in conjunction with:

• Fat deposits (neck, shoulder, tailbone)

• Difficulty losing weight

• Lameness – often without warmth or pulse in the hooves

EMS cannot be cured, but can be managed with proper feeding and management.

✅ What can you do as a horse owner?

Limit grass – especially during risk periods
• Provide access in the morning after warm nights
• Avoid access after cold nights and on sunny days
• Use a muzzle or short grazing time if necessary.

Feed with care
• Choose hay/wrap with low NSC (<10%)
• Avoid supplements with sugar, starch or fruit-based ingredients
• Water the hay if necessary – but be aware of variations in effect

Keep an eye on your body
• Weight gain, fat accumulation and stiffness may be early signs
• Consider testing insulin/glucose (e.g. via OGT)

Think holistically
• The gut, immune system and metabolism are closely linked
• Don't just focus on one thing – but on balance in the whole body

📚 Scientific basis
This article is based on research from, among others:

• Kentucky Equine Research (KER)

• ECEIM – European College of Equine Internal Medicine

• Studies published in:
  • PubMed Central (PMC)
  • ScienceDirect
  • Michigan State University College of Veterinary Medicine