This is an abbreviation of unit 11 from the Advanced Equine Nutrition course. The complete text, a video, and quiz questions are available with The Horse’s Advocate membership. You can also purchase them separately. Note: Passing the Basic Equine Nutrition Course is required before starting the Advanced Course.

Unit 11 – The Addiction Of Sugar In Horses

In humans and laboratory animals, sugar addiction is a true phenomenon; I will assume it is in horses, too, because of the similar brain anatomy, neurotransmitters, and access to sugar. Addictive behaviors driven by sugar are common in all animals consuming it. More significant than addictive behavior are the diseases associated with sugar; addiction and metabolic diseases are closely intertwined.

In humans and lab animals, sugar addiction originates from the same brain area responsible for all addictions, including heroin and alcohol, releasing the same “feel-good” neurotransmitter. However, its continuous release does not bode well for long-term survival because of the diseases created by addictive behavior. In essence, does sugar cause addiction, or does addiction cause diseases related to high sugar? Think of this one problem: eating sweet things is difficult to stop (addiction) even when we know it’s causing a metabolic crisis.

For example, lab rats fed sugar water at night show agitation as the watering time approaches, fighting each other to get to it first (is this a familiar sight with your horses?). Research on brain function shows that fructose and sucrose (glucose plus fructose) stimulate the same area that heroin does. Further, when the addicted rats were no longer fed sugar water at night, their behavior changed to one representing withdrawal, including agitation, huddling in the corner, and hair coat erection. Administering the anti-opiate naloxone while drinking the sugar water also causes these withdrawal symptoms.

Both sugar and alcohol can lead to addictive behavior and eventually cause fatty liver disease in humans. The link between cravings for sweet drinks and high alcohol consumption is well-established. However, reducing humans’ consumption of either sugar or alcohol can lead to positive changes.

By removing excess sugar from horses’ diets, we can potentially prevent the development of addictive behavior and its associated health issues. This promising concept offers hope for improving equine health and behavior through simple dietary changes, empowering us to impact our horses’ well-being positively.

Drinking alcohol also causes dehydration from increased urination. Could this dehydration also trigger the Polyol Pathway that converts glucose to fructose? Tests in laboratory mice confirmed this; increased alcohol intake creates fructose. 

To test whether alcohol or fructose caused fatty liver disease, researchers gave the same amount of alcohol to genetically altered mice who could not convert fructose to uric acid. These mice produced fructose from glucose but did not develop liver disease. This controlled experiment suggests that the breakdown of fructose via the Polyol Pathway, triggered by alcohol consumption, into fructose, and the breakdown of fructose into uric acid, is the cause of liver disease.

These discoveries are significant when applied to horses because they link fructose to addiction AND metabolic diseases.

The Foraging Response

Fructose, produced via the Polyol Pathway or eaten, drives many unusual behaviors collectively called foraging behavior, as discussed in a previous unit. These behaviors are considered addictive. Let me explain.

Foraging behaviors include impulsiveness, exploration, fast decision-making, risk-taking, and novelty-seeking. They are crucial aspects of equine behavior, driving migration to unknown lands for food without concern for the risks involved. Understanding this foraging response is critical to comprehending the potentially addictive behavior in horses caused by continuous excessive sugar consumption over time. This knowledge deepens our understanding of equine behavior, enlightening and enhancing our expertise in equine nutrition and behavior.

Fructose And The Brain

Most of the brain can absorb glucose independently of insulin, but with four exceptions:

• The hypothalamus (links the brain with the endocrine system via the pituitary).
• The hippocampus (short-term, long-term, and spatial memory).
• The corpus striatum (part of the motor and reward systems).
• The sensorineural cortex (nerves of the inner ear).

These four areas require insulin-dependent glucose uptake.

Could fructose accumulation in the brain cause IR locally before systemic IR occurs? Fructose primarily enters the liver and brain but rarely enters muscles, so IR would likely develop in the brain before IR occurs in muscles.

Today, horses, on processed foods and hay, exhibit addictive behavior, as seen in other animals and humans. But there is another component. Humans are also addicted to caring for horses in a way that may not be in the horse’s best interest. This care is hard to change, driven by industries that earn from horse owners unaware that there is something else they can do. After working through this course, you can establish a new relationship using your learned knowledge. It is simple and cost-effective. Here are the steps:

1. Eliminate all inflammatory ingredients.
2. Feed high-quality protein.
3. Record everything to see the improvements over time.

Key Points:

1. Fructose and sucrose trigger the same areas of the brain in humans that are triggered by heroin and alcohol.
2. Addiction drives unwanted behavior but also initiates metabolic diseases.
3. Uric acid from the metabolism of fructose causes addictive behavior when its presence is continuous but is essential for survival when temporary.
4. Food aggression in horses is the primary destructive behavior caused by uric acid.
5. Reducing sugar intake and fructose production reduces horses’ anxiety and food aggression.
6. Fructose can enter the brain and may create localized insulin resistance in the four parts of the brain that require insulin for glucose uptake. The reduced metabolism from IR may play a factor in developing PPID.
7. Increased fructose in the brain may result from the conversion of glucose via the Polyol Pathway. In humans, there are links between this and the accumulation of fructose, which causes a decline in the brain’s metabolic functions.
8. It is unknown if horses have uricase to break down uric acid.
9. There are signs that horses negatively alter behavior when fed a high-sugar diet and respond positively to a reduced-sugar diet.
10. Proof of horses’ addiction to sugar is unseen by most horse owners until removing dietary sugar and triggers of the Polyol Pathway improves their behavior.