Why Your Dog Needs Polyphenols - duuvk.com
Why Your Dog Needs Polyphenols

Why Your Dog Needs Polyphenols

How many times do you hear raw feeders argue that dogs don’t need fruit. “They’re carnivores!”

Whatever you feed your dog, raw or kibble, just adding fruit will change your dog’s life … and his health, with the power of polyphenols. So if you’re arguing in favor of no fruits for dogs, have a look at these top 6 reasons about why your dog should have fruit in his diet.

1. Fruit Has Polyphenols

Scientists started looking at diets rich in fruits and vegetables in the late 1900s. They learned that eating fruit helped protect people from cancers, heart disease, diabetes and more. Now they’ve learned that polyphenols are responsible for those health benefits.

Only fruit and plants contain polyphenols, which are naturally occurring compounds. When the polyphenols in fruit reach your dog’s colon, bacteria eat them. This process produces healthy by-products like short-chain fatty acids. You’ll also find polyphenols in some spices, herbs, nuts, vegetables but they are really high in fruits. Apples, pears and berries contain high amounts of polyphenols … about 200 to 300 mg per 100 grams of fresh fruit.

RELATED: Here are the best probiotics for dogs …

2. Fruit Can Reduce Cancer Risk For Dogs

Research shows polyphenols lower the risk of cancer. They inhibit cells that create DNA methylation, a major driver of cancer. They also create apoptosis … or cell death in cancer cells.

Resveratrol is a polyphenol found in fruits like apples. A study showed reduced activity of bacteria linked to colon cancer. Polyphenols like this can also limit cancer cell growth and division. So when your dog eats fruit, cancer cells are controlled and less likely to spread in your dog’s system.

3. Fruit Controls Chronic Inflammation

Inflammation isn’t always a bad thing. It’s part of your dog’s self defense system when he gets injured. If he’s sick or hurt, acute inflammation brings immune cells to the injured area. These cells fight disease and help repair tissues.

Inflammation is helpful in the short term for issues that resolve quickly. When it goes on too long it turns to unhealthy chronic inflammation.

More and more cases of chronic inflammation in dogs are leading to these common diseases: :

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

In 2014 researchers fed three groups of rats different diets for two months. One group ate rat chow while another ate a diet of high fat and high sugar. A third group ate the same high fat, high sugar diet but had cranberry juice added.

When researchers analyzed the rats’ livers, they found the rats who got cranberry juice had fewer inflammatory markers. It seems the polyphenols in the cranberries suppressed inflammatory enzymes. Polyphenols also limit cytokines which are pro-inflammatory immune cells. 

There’s another common cause of chronic inflammation. And polyphenols in fruit are valuable in fighting it too.

4. Polyphenols Are Antioxidants

Free radicals lead to inflammation. They are unstable molecules with one or more unpaired electrons. When free radicals steal electrons from their neighbors to stabilize themselves, they create more free radicals

When there are billions of molecules reacting at any given second, that’s a lot of damage to molecules. Free radicals also damage cell membranes. Free radicals build up in the body, causing chronic inflammation, chronic disease and premature aging.

Fortunately, antioxidants can control free radicals to restore the balance and provide electrons to free radicals.  Polyphenols in fruit are powerful free antioxidants. Foods like curcumin and resveratrol can really help combat oxidative stress. 

Polyphenols can sometimes be pro-oxidant, causing the same damage that free radicals do. Luckily, these free radicals seem to only seek out cancer cells. When they find them, they inject toxic amounts of free radicals into cancer cells to kill them.

When you feed polyphenols and fruits to your dog, you’re helping his body build up a credit balance, so he’s prepared to fight challenges like: 

  • Poor diet
  • Environmental toxins
  • Stress

5. Fruit Balances Your Dog’s Gut

Your dog’s food also feeds trillions of bacteria that live in his gut. Protein and healthy fats are important in feeding the friendly bacteria, which help …

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

When your dog eats starch and toxins, they feed bacteria that create inflammatory by-products. That’s why it’s important to have a strong population of friendly bacteria to crowd out the harmful bacteria. Polyphenols feed the friendly bacteria and help them flourish. 

There’s a polyphenol called catechin that limits growth of some bacteria like E coli, Bordetella bronchiseptica (kennel cough bacteria) and Salmonella. Quercetin is another polyphenol that prevents E. coli from spreading. 

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

6. Polyphenols Support The Liver

It’s a toxic world and that includes your dog’s environment. Pesticides and toxins are in his food. Plus he’s exposed to many other chemicals, drugs, vaccines and cleaners. These toxins build up in your dog’s system and lead to chronic health problems. But there’s good news … your dog’s liver can process and remove most toxins he absorbs from food and his environment.

But the liver has difficulty metabolizing toxins that are fat-soluble. So these toxins accumulate in the liver over time. And that means free radicals can also build up in the liver. 

The liver uses its own 2 step process to eliminate these fat-soluble toxins. In phase 1, enzymes neutralize toxins by converting them to less damaging molecules.

But they’re still harmful to the body. So phase 2 enzymes make those byproducts water-soluble so they can exit the body when your dog pees.

Polyphenols in fruits activate phase 1 and phase 2 enzymes in the liver. 

RELATED: 5 signs your dog needs a liver detox …

The Best Fruits For Dogs

Your dog should eat a good selection of fruits, veggies, seeds and herbs. Even wolves do this … up to 25% of their stomach contents is fruit and other plant matter during the summer. 

The nutrients of each type of fruit provide a range of health benefits and polyphenols. That means variety is important. Consider these 4 major classes of polyphenols to be sure you’re getting a good selection:

  • Flavonoids
  • Phenolic acids
  • Lignans
  • Stilbenes

Flavonoids is the largest class, with over 5,000 different compounds.


Flavonoids are valuable because they’re anti-inflammatory, help fight cancer and improve brain function. Subclasses of flavonoids include … 




Hot peppers




Genistein is an isoflavone that prevents the formation of tumors. 






Quercetin is a flavonol that can lower inflammation and combat cancer.


Red, blue and purple berries like:





Citrus fruits like:




Includes hesperidin, a special antioxidant that protects the brain.




Includes catechin that limits growth of pathogenic bacteria.

Phenolic Acids

You’ll find these free radical scavengers in the seeds and skin of fruits and in vegetables. Curcumin is a phenolic acid you’ll recognize as the active ingredient in turmeric. Curcumin disrupts cytokine activity, and that leads to a reduction in chronic inflammation. 


Lignans are antioxidants and are also useful in cancers where hormones are involved. Apricots, broccoli, leafy greens, and flax seeds are rich sources of lignans.  A 2016 study found lignans fed bacteria in the gut known to kill tumor cells.


Stilbenes include resveratrol, which you’ll find in blueberries, raspberries and mulberries. Resveratrol is well known as an anti-inflammatory and can combat cancer.

Now you know why you need to be adding fruits (as well as vegetables, herbs and seeds) to your dog’s diet. As well as nutrients, fruits and berries offer your dog remarkable disease-fighting benefits.

And if you’re thinking that your dog’s kibble contains fruits and veggies, there’s one more point to cover …

Why Kibble Doesn’t Provide Good Nutrients

Kibble requires heating and processing and that substantially reduces its nutrition and changes the food molecules. An average of 5% to 50% of vitamins are destroyed in cooked food. 

And the polyphenols you’ve been learning about? Scientists have found that many of them are destroyed when fruits and vegetables are cooked. When foods are boiled, more than half of their polyphenols are lost. Steaming results in a 20% loss. And their ability to scavenge free radicals decreases by 60% when boiled and 30% when steamed.

So fresh fruit for dogs is always best. But be aware of a few things …

When you’re feeding fruit to your dog, introduce it slowly and make sure it’s ripe. Unripened food and giving too much too soon can cause an digestive upset and diarrhea. Be careful to remove stones from fruit like plums and peaches as they can cause blockages. And use caution when feeding fruit to a diabetic dog or if your dog has a lot of inflammation. 

And even though there are great benefits to feeding your dog fruit …  remember that some fruits can be very toxic to dogs! Always double check to make sure you’re feeding dog-friendly fruits and veggies. That way your dog will enjoy all the benefits and good health fruits bring! 


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.