Is Sugar Bad for Dogs?

Dogs have a sweet tooth, just like their human companions. With functional sweet taste receptors on their tongues, dogs prefer sugary foods when they’re available. In a series of two-bowl tests reported in the Summer 1984 Neuroscience & Behavioral Reviews, Beagle puppies aged two to four months preferred sugar and nonnutritive sweeteners in semi-moist dog food over the same unsweetened food, and they preferred solutions of lactose, fructose, glucose, and galactose over plain tap water. But is sugar bad for dogs?

The Effects of Sugar on Dogs

Just as in humans, sugars and starches (carbohydrates that the digestive tract quickly converts to sugar) cause canine blood glucose levels to rise. Although the speed of blood sugar spikes varies depending on the type and amount of sugar or carbohydrate, research shows that high-glycemic treats and foods harm dogs by promoting:

• Obesity
• Metabolic disease (including diabetes)
• Dental disease
• Gut/microbiome imbalances
• Joint pain
• Cardiovascular disease

Sugar and starchy carbohydrates are key ingredients in many dog foods and treats that are inexpensive, easy to manufacture, and attractive to dogs. Many dry dog foods and treats contain up to 50% starch, so even if their labels don’t list sugar as an ingredient, they deliver a daily “sugar load” to the dogs who consume them.

Is Sugar Toxic to Dogs?

Sugar in any of its many forms will not immediately poison a dog, but sugar is not part of the natural canine diet. As interest in species-appropriate or biologically appropriate diets grows, more Americans are turning away from commercial kibble and adopting fresh, frozen, freeze-dried, or home-prepared low-carbohydrate raw or gently cooked foods based on meat, bones, and organs.

Are All Carbohydrates Equivalent to Sugar?

Fiber, the indigestible part of plants that does not break down into sugar molecules but instead passes through the body, reduces a food’s carbohydrate load. Dog foods and treats list their fiber content on their labels. Subtracting fiber from total carbohydrates gives you the product’s “net carbohydrates,” meaning the carbohydrates your dog’s body can digest.

Some carbohydrates are resistant starches, which slows their digestion in the small intestine. Resistant starches raise blood sugar more slowly than refined starches do. Green bananas, legumes, and some specially treated starches are considered resistant.

High-fiber and resistant carbohydrates may be less likely to cause the serious health problems associated with sugar, but as main ingredients in foods or treats, they both contribute to sugar-related illnesses.

Is Honey Safer for Dogs than White Sugar? What about Brown Sugar? Whole Fruits? Brown Rice Syrup?

When it comes to sweet ingredients, all natural sugars are high in carbohydrates. There is no “safe” sugar, meaning that all natural sugars can contribute to the health problems described here. You can make an ingredient like honey or sweet fruits “safe” by giving your dog small quantities infrequently, but not in large amounts every day.

The glycemic index (GI) is a scale from 0 to 100 that ranks carbohydrate-containing foods by how quickly they raise blood sugar levels. Pure glucose (dextrose), with a GI of 100, acts fastest. According to the Dietitian Prescription’s Glycemic Index Sweeteners Chart, brown rice syrup, which is sometimes incorrectly described as a healthy alternative to refined sugar, has one of the highest possible GI ratings. Fructose, barley malt syrup, and agave nectar’s GI numbers are much lower, but they are still potentially harmful sugars.

• Dextrose (Glucose): GI 100
• Brown Rice Syrup: GI 98
• Tapioca Syrup: GI 70
• Date Sugar: GI 68
• High Fructose Corn Syrup: GI 62-68
• White Sugar (Sucrose): GI 65
• Turbinado Sugar: GI 65
• Honey: GI 58
• Molasses: GI 55
• Maple Syrup: GI 54
• Coconut Sugar: GI 54
• Agave Nectar: GI 15-30
• Palm Sugar: GI 35
• Barley Malt Syrup: GI 42
• Fructose: GI 23

Sugar Contributes to Weight Gain in Dogs

According to the Association for Pet Obesity Prevention, in 2022, 59% of dogs and 61% of cats evaluated by veterinary professionals in the United States were classified as overweight or obese. Dogs easily gain weight on high-carb foods and treats.

Sugar Causes Insulin Resistance and Can Lead to Diabetes in Dogs

Insulin resistance, also known as impaired insulin sensitivity, occurs when cells in muscles, fat, and the liver do not respond to the blood sugar-lowering effects of insulin, a hormone released by the pancreas. Overweight dogs who regularly consume sugar or high-glycemic carbohydrates are at risk for diabetes, which requires daily insulin injections, carefully controlled carbohydrate intake, and lifelong management.

Sugar Causes Dental Disease and Oral Health Problems in Dogs

According to research published in Frontiers in Veterinary Science in 2020, 80% to 89% of dogs over age three have periodontal disease. Sugars in pet foods and treats contribute directly to dental plaque and tartar by altering a dog’s oral microbiome, increasing the risk of gingivitis, tooth loss, oral pain, and systemic (whole-body) inflammation and infections. Sugar-rich treats indirectly harm heart valves and other parts of the body as well as directly affecting the teeth and gums.

Sugar Causes Microbiome Disruption in Dogs

Regular sugar consumption creates microbial shifts in the digestive tract, leading to inflammation, diarrhea, gas, bloating, and even vomiting. Chronic low-grade inflammation can cause intestinal permeability known as “leaky gut,” which allows toxins, bacteria, and undigested food particles to cross the intestinal barrier and enter the bloodstream, triggering immune activation that contributes to autoimmune disorders, lethargy, recurrent infections, and slow wound healing.

Sugar Contributes to Hyperactivity and Behavioral Problems in Dogs

Rapid blood glucose variations in dogs who consume sugary foods and treats have been associated with short-term hyperactivity followed by energy “crashes” and increased hunger, behavioral problems, and weight-management challenges such as begging, food-seeking, and overfeeding habits that are difficult for dogs and their owners to break.

Sugar Causes Inflammation

Compounds called Advanced Glycation End-products or AGEs, which form when sugars bind to proteins, have been linked to chronic systemic inflammation in dogs, contributing to joint degeneration, arthritis, cognitive decline, and accelerated cellular aging.

Is Sugar Content Listed on Dog Food and Treat Labels?

Sugar content is almost never listed on dog food and treat labels, but you can learn the Dry Matter (DM) carbohydrate content of any food or treat with information that appears on the product’s package. See What to Look for on Labels.

Start by reading the first five ingredients on the label. The ingredient that weighs the most in the product comes first, and the ingredient that weighs the least comes last. Any treat whose first ingredients include obvious sugars or starches should be approached with caution. A small treat or two every few days probably won’t cause a problem, but high-carb treats given several times a day along with high-carb foods can wreak havoc with your dog’s health.

Some manufacturers provide carbohydrate content on their websites. For example, the website of a popular soft dog training treat whose first ingredients are peanut butter, potato, wheat flour, cane molasses, glycerin, peanuts, chicken fat, banana, and peas lists its Dry Matter carbohydrate content as 59%. This treat is extremely high in sugar!

Hidden Sugars in Dog Food and Treats

As you read ingredient lists of dog foods and treats, watch for all forms of sugar, which produce sharp glycemic spikes and are especially problematic in treats and semi-moist foods. These include:

• Agave nectar
• Barley malt extract
• Barley malt syrup
• Beet sugar
• Brown rice syrup
• Cane juice crystals
• Cane sugar
• Carob syrup
• Coconut sugar
• Corn maltodextrin
• Corn syrup
• Date sugar
• Demerara sugar
• Dextrose
• Evaporated cane juice
• Fructose
• Fruit juice concentrate
• Glucose
• High-fructose corn syrup (HFCS)
• Honey
• Invert sugar
• Lactose
• Maltodextrin
• Maltose
• Maple syrup
• Molasses
• Palm sugar
• Raw sugar
• Rice syrup solids
• Sucrose
• Tapioca syrup
• Turbinado sugar

High-glycemic Carbohydrates in Dog Food and Treats

Just as important are starches that a dog’s digestive system quickly converts to glucose, causing blood sugar spikes. These ingredients are not sweet to taste but they quickly break down into glucose and can make up 30% to 60% of a dry dog food.

• Rice
• Wheat
• Corn
• Potato
• Barley
• Oats
• Peas
• Chickpeas
• Tapioca
• Other processed grains, tubers, and legumes

Beware of Xylitol

Dogs are attracted to sweet tastes, including the tastes of artificial sweeteners and sugar substitutes. The most dangerous of these is xylitol, a popular ingredient in sugar-free chewing gum, mints, peanut butter, allergy medications, and other products. Even small amounts can lead to canine hypoglycemia, liver failure, and death. Read labels carefully and keep your pup away from any products containing xylitol.

Are Artificial Sweeteners Safe for Dogs?

Xylitol is by far the most dangerous artificial sweetener to dogs and should be avoided at all times. According to Emergency Vets USA, other artificial sweeteners have the following effects:

• Erythritol, used in sugar-free baked goods, candies, and weight-loss products can cause diarrhea, vomiting, and decreased appetite if consumed in large amounts.
• Stevia, one of the most popular sugar substitutes, is considered non-toxic to dogs and cats.
• Aspartame, used in sugar-free sodas, low-calorie sweets, and the sugar replacement product Equal, is unlikely to impact a dog’s health.
• Saccharine, found in Sweet N Low, is listed as non-toxic to dogs although it can cause mild gastrointestinal upset if consumed in large amounts.
• Sucralose, commonly known as Splenda, is a staple in many homes. Though generally safe for dogs, it can lead to diarrhea if consumed in large amounts.
• Monk Fruit, from a plant native to Southeast Asia, is used as a sugar replacement in some ice creams, diet sodas, protein bars, and low-fat baked goods. It is considered safe for dogs.
• Allulose, an increasingly popular sugar substitute, does not appear on the Emergency Vets USA list, but in September 2017, the Journal of Veterinary Medical Science published ”The long-term safety of D-allulose administration in healthy dogs”, which concluded that allulose is well tolerated in dogs and deserves future study because it may be appropriate in the treatment of dogs with diabetes or obesity.