Shun NagaiWhen choosing food for ourselves, we are paying more attention not only to nutritional balance and calories, but also to how food affects blood sugar levels. The same is true for pets such as dogs and cats.
In recent years, the pet food industry has been paying growing attention to an indicator known as the glycemic index (GI). GI is a numerical value that shows how quickly and to what extent a carbohydrate-containing food raises blood sugar levels.
High-GI foods tend to cause rapid fluctuations in blood sugar and are associated with health risks such as obesity and diabetes. Low-GI foods, on the other hand, raise blood sugar more gradually and are considered beneficial for maintaining satiety, managing body weight, and helping prevent disease.
In this article, we will explain the basic concept of GI and how it can be applied in pet food.
What Is GI / Glycemic Index?
The glycemic index (GI) is a numerical measure of how much and how quickly blood sugar levels rise after consuming a carbohydrate-containing food. More precisely, GI is an indicator that measures both the relative speed and degree to which a particular carbohydrate raises blood sugar levels in dogs and cats.
Types of GI Foods
Basically, GI foods can be divided into two categories: low-GI foods and high-GI foods. Low-GI foods are digested more slowly, allowing pets to maintain energy for a longer period of time.
High-GI foods, by contrast, are rapidly digested and cause an immediate spike in energy, but this is usually followed by a sharp energy drop.
Under the GI system, foods are rated on a scale of 1 to 100. Foods with a GI of 55 or lower are classified as low GI, 56 to 69 as medium GI, and 70 or higher as high GI. In other words, the higher the GI value, the greater the risk that a dog’s or cat’s blood sugar level will rise too quickly to an unhealthy level.
| GI Category | Score |
|---|---|
| Low GI | 55 or below |
| Medium GI | 56–69 |
| High GI | 70 or above |
It is also useful to remember that glucose itself has a GI of 100. This makes the GI scale easier to understand. GI can be a valuable tool for making healthier choices for dogs and cats, and for developing the “right” food suited to individual needs.
Why Low-GI Pet Food Is Important
Choosing low-GI food is very important when considering the health of dogs and cats. This is because regularly consuming high-GI foods can lead to repeated spikes and crashes in blood sugar, increasing the risk of various health problems.
Excessive Strain on the Pancreas
Carbohydrates with a high GI are rapidly absorbed and converted into glucose, making them an immediate source of energy. At the same time, however, they cause a sharp rise in blood sugar, triggering an excessive insulin response from the pancreas.
Insulin is a hormone secreted by the pancreas that lowers blood sugar levels. When pets consume high-GI foods, the pancreas is forced to work harder to produce enough insulin, placing it under strain.
Overeating Caused by Hunger
In dogs and cats as well, excessive rises in blood sugar can contribute to obesity. This is because when blood sugar rises sharply, the pancreas releases a large amount of insulin in response.
Insulin quickly lowers blood sugar, but this rapid drop can signal to the brain that the body is running low on energy, triggering a sensation of hunger.
In other words, even when the body still has sufficient energy, dogs and cats may seem hungry again shortly after eating because of these rapid blood sugar swings.
In addition, because insulin promotes the storage of excess glucose as body fat, repeated cycles of blood sugar spikes can make pets more prone to obesity over time.
Disease Risks Associated with High-GI Foods
As a result, the following diseases and health risks may occur:
Type 2 diabetes (mainly in cats), Type 1 diabetes (mainly in dogs), osteoarthritis, hypertension, hyperglycemia, heart disease, and cancer.
Benefits of Low-GI Pet Food
A diet centered on low-GI foods is considered beneficial for pets because studies suggest that low-GI pet food can provide a variety of health advantages for dogs and cats.
Helps Pets Stay Full Longer
Low-GI foods are characterized by slower digestion and absorption. As a result, the rise in blood sugar after a meal is more gradual, and the corresponding release of insulin is also steadier.
This stability in blood sugar and insulin plays a major role in maintaining satiety. When a pet eats a high-GI food, blood sugar rises rapidly, followed by excessive insulin release, which then causes blood sugar to drop sharply. This sudden decline can signal hunger to the brain, making the pet feel hungry again soon after eating.
With low-GI foods, blood sugar rises more slowly and remains more stable, and insulin release is gentler as well. As a result, dogs and cats are less likely to feel hungry soon after meals and are better able to stay full for longer periods.
Helps Control Diabetes Symptoms
Low-GI carbohydrates are digested and absorbed slowly, so they do not cause a rapid spike in blood sugar. This reduces the need for the pancreas to secrete excessive amounts of insulin and helps stabilize blood sugar control.
Cats in particular are prone to insulin resistance, meaning they cannot use insulin properly. This mechanism is similar to type 2 diabetes in humans. Switching to a low-GI diet can help prevent sudden blood sugar spikes and may contribute to improved insulin sensitivity.
May Reduce the Risk of Heart Disease
A high-GI diet tends to cause chronic high blood sugar and excessive insulin secretion, which can promote inflammation and vascular damage. Over time, this puts additional strain on the heart.
Low-GI diets help stabilize blood sugar and may slow the progression of arteriosclerosis, thereby reducing stress on the heart and potentially helping prevent or improve heart disease such as cardiomyopathy and heart failure.
Helps Lower Blood Cholesterol Levels
High-GI foods can negatively affect lipid metabolism and may lead to increases in LDL (“bad”) cholesterol and triglycerides.
Low-GI carbohydrates, especially ingredients rich in dietary fiber such as barley and lentils, are believed to help improve blood lipid balance by binding cholesterol and promoting its excretion.
Supports Physical Endurance
High-GI foods can provide a quick source of energy, but they may also lead to a sudden energy crash afterward.
Low-GI foods release energy more gradually, which helps maintain stable stamina. This is especially important for active dogs, senior pets, and working dogs such as police dogs and guide dogs, all of which rely on a steady energy supply to stay healthy.
Common Pet Food Ingredients and Their GI Values
Low-GI Foods
| Ingredient | GI Value |
|---|---|
| Barley | 25 |
| Lentils | 29 |
| Apple | 38 |
| Carrot | 47 |
| Yam | 37 |
| Brown rice | 55 |
| Quinoa | 53 |
| Oats | 55 |
| Sprouts | 25 |
| Green beans | 15 |
| Sweet potato | 50 |
| Blueberries | 44 |
| Peas | 48 |
High-GI Foods
| Ingredient | GI Value |
|---|---|
| Potato | 76 |
| White rice | 72 |
| Tapioca | 70 |
| Whole wheat flour | 60–70 |
How to Tell Whether a Food Is High or Low GI
Although it is not possible to determine glycemic load (GL) precisely on your own, there are many online resources that explain GI values, how GI works, and what types of pet food to choose. One useful resource is the University of Sydney’s Glycemic Index search database.
Website: https://www.glycemicindex.com
While the glycemic index (GI) is a basic tool for determining whether a food is low or high GI, it is also worth understanding another term: glycemic load (GL).
Glycemic load measures both the quality and quantity of carbohydrates in a food. In other words, it indicates both how quickly a food raises blood sugar and how much carbohydrate is contained in one serving.
To calculate the glycemic load of a specific food, use the following formula based on the GI and the amount of carbohydrate it contains:
GL = GI × grams of carbohydrate ÷ 100
Here is a simple example using white rice. About two-thirds of a cup of white rice contains approximately 36 grams of available carbohydrates, and its GI is 72. Therefore, the calculation is as follows:
72 × 36 = 2,592 ÷ 100 = 25.92 (glycemic load)
While the glycemic index helps identify suitable foods for pets, glycemic load is useful for comparing how serving sizes of different foods affect blood sugar.
Another helpful tip is that many low-GI wet and dry pet foods also tend to be grain-free.
GI in the Pet Food Industry
The U.S. Food and Drug Administration (FDA) has not issued a formal position on glycemic index, nor is there an official protocol for testing the GI of pet food. This is mainly because determining the actual GI value of many commercial pet foods is complex.
One challenge in identifying the true GI of dog and cat food lies in both the food itself and the way it is prepared. Most pet foods are made from multiple ingredients with different chemical and physical structures, and they are also processed using different methods and degrees of refinement. As a result, accurately evaluating GI can be difficult.
It is also important to note that GI values are influenced not only by the content of the food and how it is processed, but also by the fact that not all pets respond to the same food in exactly the same way in terms of blood sugar.
Therefore, GI values used for pet food should be regarded as general guidelines. They may not fit every specific need, nor do they necessarily apply consistently to all dogs and cats.
Even so, given the scientific evidence supporting the health benefits of low-GI pet food, the glycemic index remains one of the most useful guides for pet owners seeking healthier and more nutritious food for their dogs and cats, especially from the standpoint of weight management and weight-related diseases.