Fruits For Dogs: Why Your Dog Needs More Polyphenols

fruits for dogs

There are a lot of raw feeders who say “Fruits for dogs? Carnivores don’t need them!”

But it doesn’t matter if you feed raw, kibble or otherwise. Fruits have the ability to change your dog’s life … in a very good way.

If you’re in the No Fruits For Dogs camp, I’m hoping to change your mind with these top 6 reasons to feed your dog more fruit … 

1. Fruit Contains Polyphenols

In the late 1900s, scientists looked at diets rich in fruits and vegetables. They found they protected people from cancers, heart disease, diabetes and more. Today, they know those health benefits come from polyphenols.

Polyphenols are naturally occurring compounds that come only from fruit and other plants. But when your dog eats fruits, he can’t actually digest polyphenols directly. The polyphenols travel to his colon, where bacteria eat them. The bacteria then produce healthy by-products like short-chain fatty acids.

Polyphenols are in some spices, herbs, nuts, vegetables but are especially high in fruits. Apples, pears and berries contain about 200 to 300 mg of polyphenols per 100 grams of fresh fruit.

2. Fruit Can Kill Cancer Cells In Dogs

Studies show that polyphenols reduce the risk of cancer. This is because they can inhibit cells that cause DNA methylation, which is a major driver of cancer. They can also reactivate silenced genes in cancer cells and cause their death (apoptosis).

A study looked at resveratrol, a polyphenol found in fruits like apples. It showed that resveratrol reduced bacteria activity linked to colon cancer. This polyphenol and others can also control cancer cell growth and division. This means when your dog eats fruit, cancer cells are less likely to spread in your dog’s body.

3. Fruits Reduce Chronic Inflammation

Inflammation is a natural part of the body’s defense system. When your dog is sick or hurt, acute inflammation delivers immune cells to the affected area. Once there, the cells help to fight disease and repair damaged tissues.

So inflammation is helpful … but only if it’s short term and resolves quickly. If acute inflammation continues it becomes unhealthy chronic inflammation.

Unfortunately, chronic inflammation is becoming a common problem in dogs that’s linked to:

  • Cancer
  • Allergies
  • Heart disease
  • Joint disease
  • Diabetes
  • Autoimmune diseases

In a 2014 study, researchers fed three groups of rats differently for two months. The first group ate rat chow and the second ate a high fat, high sugar diet. The third ate the same high fat, high sugar diet with some cranberry juice added. The researchers then analyzed the rats livers.

The rats fed the cranberry juice had fewer inflammatory markers. The polyphenols in the cranberries suppressed inflammatory enzymes. They also inhibited pro-inflammatory immune cells called cytokines. 

Polyphenols in fruit can also help your dog fight another common cause of chronic inflammation … 

4. Polyphenols Fight Oxidative Stress

Free radicals are another important cause of inflammation. Free radicals are unstable molecules with one or more unpaired electrons. But electrons like to be paired, so free radicals steal electrons from their neighbors to tray and stabilize themselves. This causes the neighboring molecule to become unstable, creating more free radicals.

Billions of molecules can react every second leading to a lot of damage to molecules. It’s especially harmful to cell membranes. Free radicals build up like rust in the body. And this rust causes chronic inflammation and ultimately chronic disease and premature aging.

Antioxidants fight free radicals. They work together to donate an electron to the free radical … without becoming free radicals themselves.

Polyphenols in fruit are potent free radical scavengers. Feeding fruit can really help combat oxidative stress

Sometimes polyphenols can be pro-oxidant … and cause the same damage that free radicals do. But these free radicals only seem to target cancer cells. And they pump toxic amounts of free radicals into cancer cells to kill them.

Think of feeding polyphenols and fruits as making deposits into your dog’s bank account. These deposits help your dog’s health account to stay balanced and healthy against:

  • Environmental toxins
  • Stress
  • Poor diet

5. Polyphenols In Fruit Balance Your Dog’s Gut

When you feed your dog, you’re also feeding the few trillion bacteria that live in his gut. Some foods, like protein and healthy fats, have important responsibilities. They feed the friendly bacteria in his gut. These friendly bacteria help your dog in many ways. They …

  • Produce your dog’s vitamins
  • Protect his gut lining
  • Help modulate his immune system

Toxins and starch in your dog’s diet can feed the bacteria that produce inflammatory by-products. But when there’s a good population of friendly bacteria, they can crowd the harmful bacteria. They do this by competing for receptor sites in the intestines. 

Polyphenols feed the friendly bacteria and can bind to receptor sites on harmful bacteria. This interferes with their activity and growth so that the good bacteria can thrive.

The polyphenol, catechin, can stop the growth of bacterias. This includes E coli, Bordetella bronchiseptica (kennel cough bacteria) and Salmonella. Another polyphenol called quercetin can also stop E. coli from growing. 

RELATED: Why your dog’s allergy treatment doesn’t work …

6. Polyphenols Help Detoxify The Liver

Today’s world is toxic. Your dog’s environment is toxic. His food contains pesticides and other toxins. Not to mention the number of other chemicals, drugs, vaccines and cleaners he’s exposed to …

All these toxins build up in your dog and cause chronic health problems. The good news is your dog’s liver can process and remove most toxins from food and the environment.

But some toxins, especially fat-soluble toxins, are hard for the liver to metabolize. Instead, these toxins cling to liver cells and build up over time. And this can cause free radicals to also build up in the liver. 

Luckily, the liver has a 2 phase process to remove these fat-soluble toxins. Phase 1 is the first step in defending the liver from toxins. During Phase 1, enzymes help neutralize toxins by converting them into less harmful molecules.

But these molecules can still be harmful to the body. So phase 2 enzymes take those byproducts and make them water-soluble so they can easily exit the body.

Polyphenols in fruits support your dog’s liver by activating phase 1 and phase 2 enzymes in the liver

RELATED: Spot the early signs of liver disease in dogs …

What Are The Best Fruits For Dogs?
Fruits, veggies, seeds and herbs can, and should, be an important part of your dog’s diet. Even wolves scour their environment for fruits and veggies. In the summer months, up to 25% of their stomach contents is fruit and other plant matter.

But variety is key! Because each fruit gives your dog different health benefits and polyphenols. To help you select a good variety of fruits (and vegetables) for your dog, you want to consider 4 major classes of polyphenols:

  • Flavonoids
  • Phenolic acids
  • Lignans
  • Stilbenes

Each of these classes has subclasses. The largest of which is flavonoids with over 5,000 different compounds.


Flavonoids are anti-inflammatory, have cancer-fighting properties and improve cognitive function. Flavonoid subclasses include:

Hot peppers

Also includes genistein, which can prevent tumor formation. 

Also includes quercetin, which can reduce inflammation and fight cancer.

Red, blue and purple berries like:

Citrus fruits like:
Also includes hesperidin, a special antioxidant that can protect the brain.


Also includes catechin, which inhibits the growth of pathogenic bacteria.

Phenolic Acids

Phenolic acids are in the seeds and skin of fruits and in vegetables. And they love to scavenge free radicals. One of the most notable phenolic acids is curcumin, which is the active ingredient in turmeric. Curcumin disrupts cytokine activity, which decreases chronic inflammation. 


Lignans are in apricots, broccoli, and leafy greens, and flax seeds are a very rich source. They play a role in hormone-associated cancers and they can also be antioxidants.

There’s a study from 2016 that looked at lignan. Researchers found it fed bacteria in the gut known to have tumor cell killing activity.


Stilbenes include resveratrol, which is in blueberries, raspberries, mulberries, and peanuts. Resveratrol is anti-inflammatory and can fight cancer.

So if you’re not adding fruits (as well as vegetables, herbs and seeds) to your dog’s diet … you need to. Fruits and berries offer your dog significant disease-fighting benefits.

Now you might be thinking, “those fruits and veggies are already in my dog’s kibble.” And that leads to the final note … 

Why Kibble Isn’t A Good Source Of Nutrients
Heating and processing food reduces its nutrition. Heating changes molecules. On average, 5% to 50% of vitamins get destroyed when you cook food. 

Scientists have found that cooking fruits and vegetables destroy many of the polyphenols. Boiling foods can remove half their polyphenols. Steaming can cause a 20% loss. And the free radical scavenging activity decreases by 60% with boiling and 30% with steaming. 

So fresh is always best when it comes to fruits for dogs. But there are a few words of caution …

You must feed fruit when it’s ripe and introduce new fruits in small amounts. Otherwise, it can cause an upset stomach and diarrhea. Be careful about stones in fruit like plums as they can cause blockages. And finally, don’t overfeed fruit to diabetic dogs or if your dog is very inflamed.

And remember … some fruits can be very toxic to dogs! So always double check to make sure that the fruits and veggies you’re feeding your dog are good for him. That way your dog can enjoy all the benefits fruits have to offer!

Ready to start feeding your dog fruits? Find out which ones are safe for your dog to eat.


Kim MJ, Kim JH, Kwak HK. Antioxidant effects of cranberry powder in lipopolysaccharide treated hypercholesterolemic rats. Preventative Nutrition and Food Science. 2014;19(2):75-81.

Cui X, Jin Y, Hofseth AB, Pena E, Habiger J, Chumanevich A, Poudyal D, Nagarkatti M, Nagarkatti PS, Singh UP, Hofseth LJ. Resveratrol suppresses colitis and colon cancer associated with colitis. Cancer Prevention Res (Phila). 2010 Apr;3(4):549-59.

Fang M, Chen D, Yang CS. Dietary polyphenols may affect DNA methylation. Journal of Nutrition. 2007;137(1 Suppl):223S-228S.

Hwang IG, Shin YJ, Lee S, Lee J, Yoo SM. Effects of different cooking methods on the antioxidant properties of red pepper. Prev Nutr Food Sci. 2012;17(4):286-292.

Zhou Y, Zheng J, Li Y, et al. Natural polyphenols for prevention and treatment of cancer. Nutrients. 2016;8(8):515. Published 2016 Aug 22.

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