Is Soy Bad for Dogs?

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We are now up to the letter “S” in our dog food ingredient series. Today we are writing about the somewhat controversial Soy, an alternative protein source in some dog foods.


What is Soy?

Soy and its derivatives come from the soybean, a legume that is native to East Asia.


Common names for Soy

Common names for soy include soybean, soya bean, large bean and yellow bean. In dog food we see soy listed in many forms including soy protein, soy flour, soybean meal, soy fiber, soybean mill run and soybean oil.
green soybeans on white background

Why is Soy in Dog Food?

Soy is added to dog food because it is an inexpensive source of protein. Soy is also a good source of the many vitamins and mineral (see below).


Is Soy Commonly Used in Dog Food?

Soy is a fairly common ingredient in dog food. We found soy in about 17% of all dog foods. It is used often in both dry and wet recipes.


Common Benefits or Risks of Soy

Soy is high in protein and omega 3 fatty acids, as well as B vitamins, vitamin K, and the minerals iron, manganese, and zinc.

There is some research that supports other health benefits of soy:

Diabetes: research suggests that taking soy products reduces blood sugar levels in people with diabetes.

Cardiovascular health: researchers at the College of Medicine at the University of Kentucky analyzed previously published studies involving soy protein and risk of coronary heart disease (CHD) and found an overall decreased risk of CHD when approximately 30 grams of soy protein was consumed on a daily basis.

Cancer: although there is conflicting evidence, some studies that suggest that diets containing ample soy can lower the risk of some cancers including lung and thyroid cancers.

Brain function: some research suggests soy can improve memory.


Despite the aforementioned benefits, there is also a growing number of health concerns regarding the long term use of soy, some of which are in direct contradiction to benefits reported elsewhere. In an article published in the Huffington Post, Dr. Mercola lists several possible risks including malnutrition, digestive distress, immune system breakdown, thyroid dysfunction, cognitive decline, reproductive disorders and infertility and even cancer and heart disease. One of the primary reasons that soy is so controversial regarding its benefits and risks has to do with how it is farmed and processed.


GMO and Pesticides: according to the New York Times, more than 90% of the soybean crop in the U.S. is genetically modified. Further, a majority of the soybean crops are heavily sprayed with chemical pesticides, some of which are linked to cancer.


Anti-nutrients and Fermentation: soybeans contain “anti-nutrients” such as saponins, soyatoxin, and phytoestrogens. Traditional fermentation destroys these anti-nutrients, enabling the body to enjoy soy’s nutritional benefits. Commonly used fermented soy products include Miso and Soy Sauce. Some of the adverse health effects due the anti-nutrients in soy include reduced assimilation of many minerals, reduced protein digestion, pancreatic disorders, and thyroid problems to name a few.


A 2004 study was conducted at the University of Pennsylvania to determine the amount of phytoestrogens in 24 random commercial dog foods. Results revealed all the foods containing soy ingredients had concentrations of phytoestrogens (an antinutrient) in large enough quantities to have a biological effect on the pet in the long term.   Said another way, the levels of soy in the randomly selected foods were high enough to be a concern if ingested over time.


Soy has been linked to gas and deadly bloat in dogs. It is high in purines and is therefore not an appropriate protein source for urate-forming dogs.

slimdoggy frown 

Slimdoggy Ingredient Comfort Level

Most normally healthy dogs should obtain their protein from the flesh of animals, not from plants or legumes like soy. Furthermore, unfermented and nonorganic soy, the form that is used in dog food, appears to have significant health risks with long term use. Thus, we give soy the SlimDoggy frown.


Miscellaneous Facts about Soy

Soy plants can grow as high as 6 feet.

Once a crop found only in the Far East, soybeans are now a major crop in the United States, Brazil, Argentina, and India.


Sources and further reading


Editor’s note: to view all of the dog food ingredients we have covered, search on the tag “ingredients” or click here:

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  1. I agree with you, we stay away from food with soy. It has a very bad aftereffect, you can’t stay with Easy in one room when he had food with soy beans…not even for 5 minutes :o)
    easy rider recently posted…easyblog MISCHIEF MOANDAYMy Profile

  2. Agreed!! Soy gets the sibe frown too!
    ღ husky hugz ღ frum our pack at Love is being owned by a husky!
    Jenna,Mark “HuskyCrazed” Drady recently posted…Proud to have PrideBites – Day #2 SALE!My Profile

  3. Hubby & I, and Callie, all have to take thyroid pills to regulate our hypothyroidism so I do my best to avoid soy in anything. However, I have yet to find a multivitamin that does not contain at least a trace of soy. But all 3 of us have annual blood work done that includes a thyroid test, so I don’t worry about it too much. Shadow and Ducky seem to be “normal”, though Shadow is borderline. We just have to keep an eye on her.
    Callie, Shadow, and Ducky’s Mom recently posted…Getting Revenge on the DuchessMy Profile

  4. Such a gassy food for me, I try to stay away from it myself. Can’t imagine both Harley and I eating it – Phew…

  5. It’s interesting soy has both positive and negative effects on people as well. Having a deep chested dog that could be prone to bloat, this is good information to know. Thanks!
    Elaine recently posted…Tips for a Holiday Road Trip with Your DogMy Profile

    • You’re welcome…we want to keep our friends healthy!
      mkob recently posted…Is Soy Bad for Dogs?My Profile

  6. Soy doesn’t sound good to us either.

  7. I totally agree. I avoid soy because of the GMO implications.
    Jan K recently posted…Tuesday’s Tails – Happy National Mutt DayMy Profile

  8. Any product used to create a cheap and filling ingredient in dog food can be a bad idea.

    On the other hand, I found that giving a small amount of tofu to my dogs every day helped treat their spay-related incontinence. And it meant I didn’t have to pay for estrogen pills.
    Pamela recently posted…12 Things I Learned While Fostering DogsMy Profile

    • Interesting. Jack has a little of that age-related incontinence and is on meds for it.
      mkob recently posted…Is Soy Bad for Dogs?My Profile

      • I wouldn’t expect the soy to work for Jack. The reason it works for female dogs is because soy has isoflavones that mimic the effect of estrogen.

        I assume Jack’s med is not estrogen.
        Pamela recently posted…12 Things I Learned While Fostering DogsMy Profile

        • Nope – Proin (Phenylpropanolamine)- works by increasing the sphincter tone of urethra, which tightens the bladder sphincter muscles thereby preventing urine leakage.
          mkob recently posted…SlimDoggy Wishes Come True?My Profile

  9. Wow didn’t know about the health concerns.
    Sand Spring Chesapeakes recently posted…Wordless Wednesday~Really? No More Photos!My Profile

  10. I am perfectly comfortable with soy as an ingredient. Neither of the foods we use have it as an ingredient, but I would not discount a food I otherwise like if it was an ingredient.
    2 Brown Dawgs recently posted…Thursday Barks And Bytes–Odds And Ends From VacationMy Profile

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