Sodium Selenite in Dog Food — Vital Nutrient or Dangerous Toxin?


Sodium selenite can be controversial substance when it’s used in a dog food recipe.
Selenium Capsule for Use in Dog Food
That’s because although the mineral is essential for normal cell function in all animals, selenium can be toxic in high doses.

What’s worse, the mineral’s toxicity also seems to be related to the chemical form used to make a each recipe.

Natural Selenium — or Sodium Selenite?

For example, one study using rats (not dogs) suggested sodium selenite was 2.94 times more toxic than natural selenium yeast.1

This more natural and organic form of selenium produced by yeast is known as selenomethionine. And based upon human studies, this compound is not only less toxic, it also more closely mimics the form of the mineral found in fresh food.2

So, it’s more biologically available to the animal.

Why Any Mineral Can Be Toxic

To be fair, it’s important to note that any mineral (copper, calcium, phosphorus, zinc, etc.) or vitamin can become toxic when fed in excessive amounts.

This dangerous “over-nutrition” condition is known as toxicosis.

The 2010 Blue Buffalo dog food recall is a perfect example of how even too much of a vitamin (in this case, vitamin D) can be toxic.

How Much Selenium Is Too Much?

According to AAFCO, the maximum amount of selenium used in a dog food should not exceed 2.0 mg/kg on a dry matter basis — or about 18 times the recommended minimum of 0.11 mg/kg.

And on a caloric basis, the maximum suggested selenium content is 0.57 mg per 1000 calories of food — which is about 19 times the minimum 0.03 mg for the mineral.

Although AAFCO sets a maximum for most minerals, the National Research Council3 has yet to determine the safe upper limit for many inorganic nutrients — including selenium.

Why It’s Controversial

The controversy appears to be over the use of sodium selenite to supply trace amounts of selenium to a dog food.

Those opposed to sodium selenite — or its close chemical cousin, sodium selenate — are concerned about what they believe to be a notably thin margin of safety between an effective “dose” of the mineral and the amount that could cause toxicity.

So, a supplement supplier that provides slightly too much selenium to a commercial nutrient mix could make it easy for a dog owner to unknowingly administer a toxic dose to her pet over an extended period of time.

Although this concern could certainly be justified, history doesn’t appear to support this view.

The Bottom Line

Unfortunately, it looks like the sodium selenite controversy might be creating unnecessary concern for dog owners. And favoring selenium yeast as a source of selenium might be a better idea.

“Indeed, selenium has an excellent safety record, and the only cases of selenium toxicity, which occurred several decades ago, were due to inadvertent dosage errors by inexperienced supplement manufacturers which were not using selenium yeast or selenomethionine in their products.” 4

However, simply seeing the words “selenium yeast” on a dog food ingredients list is no guarantee of quality. After all, some of these items may have been made with yeasts containing sodium selenite instead of the preferred organic compound — selenomethionine.

What’s more, the overwhelming majority of dog foods — even some of the very best — contain the sodium selenite version of selenium.

Since only a handful of foods are made with biologically superior selenium yeast, avoiding sodium selenite may be impractical.

What Can You Do?

Unfortunately, not much. That’s because when it comes to vitamin or mineral toxicity of any kind, it’s a matter of trust.

It’s more a matter of trusting a manufacturer to seek out quality supplements — and add them accurately — with care — to each batch.

Although no one can assure you any dog food will be 100% safe from containing excessive amounts of any mineral, you can take at least some comfort in the reasonable margin of safety between the AAFCO minimums and maximums for selenium.

In any case, those who still consider themselves “selenite-phobic” should simply look for foods that contain selenium yeast rather than sodium selenite.

And be sure to check out my review of your favorite brand. Look in the yellow dashboard area for the included ingredients. Sodium selenite — if present — is typically located near the end of the list.


  1. Vinson, J.A. and Bose, P., ‘Comparison of the Toxicity of Inorganic and Natural Selenium’ in `Selenium in Biology and Medicine’, Edited by: Combs, G.F., Levander, O.A., Spallholz, J.E. and Oldfield, J.E. Van Nostrand, NY., 1987
  2. Schrauzer GN, “Nutritional Selenium Supplements: Product Types, Quality, and Safety”, J Am Coll Nutr February 2001 Vol 20 No 1, pp 1-4
  3. National Academies of Science
  4. Schrauzer GN, “Nutritional Selenium Supplements: Product Types, Quality, and Safety”, J Am Coll Nutr February 2001 Vol 20 No 1, pp 1-4
  • Jennifer Huynh

    I have been buying my dog great quality food, from the honest kitchen company. She is a chihuahua so her food box will last for months. Recenlty i bought the exact same food for her and now the new thing added was this ingredient. Didnt realize it until i open the package.It kind of pissed me off, not only upset with myself but with the company as well.Have been a loyal customer. The difference I notice was that the food was more greener than the last same box of food without the ingredient. I don’t care of its a little bit greener as long as it doesn’t have any crap in it. That is why i bought and trust this brand of food. She doesn’t eat only this food but fresh and cooked veggies and fruits.

  • LunaLove

    it is weird that i was also told 2% about a year ago thats why i stopped feeding the trout and salmon and accoding to zignature at the time duck or lamb was the least so i choose to rotate between them. now i am seeing people say they were told trout and salmon was 2% awhile ago and now recently that it is much lower. so i emailed the company stating that everyone is getting different sodium levels. i still have the email from a yr ago saying it was 2% for trout and salmon. she said that was worng and gave me a list of % for every formula. i asked of any formula changes bc im wondering how they told everyone 2% and now its much lower. either way it seems the only dog food my dogs tolerate and the customer service even though it may have been wrong or updated has always gotten back to me right away and are very nice.

  • Francesca G

    I recently called their office several times and I talked to the woman and the dude who answer the phone. Salmon & Trout is around 2% sodium (I was told they just increased the sodium). The sodium used to 1.5%. Zignature has two fish lines one is Salmon Formula and the other line is Salmon & Trout Formula. Both have VERY high sodium levels. If you look on their website you will see they list all of their ingredients, proteins, fat etc but they do NOT list the sodium levels. If you read the comments below many people complained that their dogs were thirsty. Once I took my dog off Zignature she wasn’t as thirsty. She went from drinking 3 small bowls a day back to 1 1/2 small bowls per day.

  • Krissy Wejrowski

    2% is not true. I contacted them and they said the sodium level of that dog food is 0.57% MAX. All the sodium levels are listed under the comment section on their Facebook page if you’d like to look.

  • Krissy Wejrowski

    2% is not true. I contacted them and they said the sodium level of that dog food is 0.57% MAX. All the sodium levels are listed under the comment section on their Facebook page.

  • DQ

    Hi all,
    The only way to know if there is toxicity or deficiency, is to test the animal. If you want to know how much Selenium is in the other ingredients BEFORE they add Selenium, YOU have to test each individual ingredient first.
    You would be surprised how much Selenium is in Soybeans. If it is grown in South Dakota or Nebraska and some other states, it will be way higher than you think.
    Nobody would be the wiser if the animal did get sick or die from Selenium Toxicity because it mimics too many diseases. So testing is the only way to be sure. The problem is who is going to think to test the animals for Selenium levels?

  • Washington Gail

    first response that kind of makes sense to me.

  • Francesca G

    Zignature Trout & Salmon contains this ingredient. My dog was always thirsty while eating their kibble. I switched my senior dog from Zignature to Acana and my dog is no longer as thirsty. I called Zignature and I found out their sodium level is 2.00% which is very bad for a dogs heart. Stay away from Zignature and they do NOT list their sodium intake on the back of their bags. Red flag!!

  • TTeddy

    There’s a lot you can do about it. Don’t feed your pet processed pet food, easy. You have no idea what’s in it. There’s no guarantee that all ingredients are listed on the packaging.

  • Dee

    Great article! Now I understand why we use organic selenium yeast as opposed to sodium selenite in our foods.

    Dee Ivins
    Nature’s Select Super Premium Pet Foods

  • Mister Wu

    High selenium yeast contains mostly the selenium amino acid seleniomethionine which is less toxic as it substitutes for methionine in proteins. Inorganic selenium which is toxic in high doses however metabolical can become selenocystine and then part of the glucothione peroxidase system with all the outstanding health benefits. Selenomethionine doesn’t. Thyroid health and cancer cell apotosis,etc. This is one strange example where inorganic mineral may be better and the common organic yeast not so beneficial at all. Human population studies have shown selenite or selenate lowering cancer cases significantly, selenium nutritional yeast just slightly.

  • victor dog foods claims that selenium yeast is its sole

    source of added selenium.

  • Shar Tay

    RedMoon Customized Petfood has selenomethionine. 

  • christos_mama

    Thanks for all you do Mike S

  • michael s

    The msds for sodium selenite gives it a 3 for health, thats pretty bad.. I will look for sodium selenite free foods in the future. I read that sodium selenite accumulates over time in your dog so long term effects can sure be worse than the immediate toxic effects. Yeah I guess in a couple of years sodium selenite will be in the same category as menadione and they that defend it will become less and less. Why gamble with your pets I wont

    link for msds

    link for NTP Technical Report on Toxicity Studies of
    Sodium Selenate and Sodium Selenite

  • One more point. Selenium yeast still appears to be a biologically superior source of this essential trace mineral.

    For the record, I’m beginning to notice more and more products using this more natural form of selenium in some of newer and updated recipes.

    Sodium selenite was the first form of selenium approved for use in pet foods back in the 1970s. So, you’ll still see lots of it in pet food.

    Hopefully, this changeover to selenium yeast will begin to take over in the future. But I’m not holding my breath.

  • Toxed2loss

    LOL, sometimes it’s a relief to not wear one. They’re really hard to breathe through. And if it was toxic, I couldn’t even get near enough to pick it up. If I’m working sheep, it’s one of those blessedly clean days where the air is clear and heavenly to breathe. A little dirt (minerals) tastes and smells good! GFETE

  • Toxed2loss

    LOL thanks Labs, but I think in both our cases, for sure mine it’s more like “trial by fire.” ;-P

  • someone11111

    Yes, i definitely feel better, if @Toxed2loss:disqus is not worried, (cuz Toxed is VERY particular about ingredients!) that is comforting.  but IS that really you there, Toxed?  has someone taken over your keyboard while you were making a drink or something?

    (just joking)
      THANK YOU for info, everyone…so i don’t need to google “symptoms of selenium toxicity in dogs” then?  And Toxed, wear a facemask for pete’s sake!  

  • someone11111

    THANK YOU ALL!! where is the “love” button under each of these comments, and thank you also to Mike, for being so kind to reply, and, for this most awesome site, which i have linked about a bazillion times all over the net, cuz it is the BEST of all dog food rating sites, imo.

    darn my ability to “like” all these comments below is not working today.  (braces for LabsRawesome to tease me about this ongoing lack of basic computer skills, but for real, i can “like” the comment, and then, POOF! it disappears again, so everyone pretend there is a “like” under your comment.)  Hey, Labs, will you please “like” all the comments for me? thanks. ha ha.

  • LabsRawesome

     Toxed, that helps me. But, I really wasn’t all that worried about it. 🙂  I swear you and Shawna are like geniuses or something. Seriously.  🙂

  • Toxed2loss

    I hope this doesn’t muddy the waters even more. Selenium is a TRACE mineral. The necessary amount is a very narrow margin. Too little, you sicken and die. Too much, you sicken and die. But the quantity your dealing with here is tiny!

    Sodium selenium appears to be more toxic, but the fungal medium they’re growing the alternative on has issues of its own. Let’s take a step back and a big breath.

    I feed loose trace mineral to my livestock. It includes sodium selenium. I can pour the bag of loose dusty minerals into the feeder without adverse effect. As a walking, talking toxin detector, I’m here to tell you, in these minute quantities, it’s the least of your worries. Does that help?

  • Jess

    From what I have read it is only sodium selenite that is bad.

  • Hi Someone11111,

    You make a logical point. However, the problem unique to sodium selenite is that (as I mention in my article) one study showed sodium selenite 2.93 times more toxic than the natural form of selenium produced by selenium yeast.

    And this narrower margin of safety can make accurate dosing in a dog food’s supplement more critical.

    In any case, even though sodium selenite is controversial and since any mineral or vitamin can be toxic in excessive doses, I’ve decided to deactivate the red flag function for this form of the mineral.

    Thanks for your sensible comment.

  • someone11111


    Since selenium is both a needed nutrient,but is dangerous in too large of doses,
    thenshould not ALL vitamins be flagged in red lettering as this is true of many fat-soluable vitamins, as well?As well as salt, potassium, etc,————
    all are needed ingredients,
    BUT, too much is dangerous….so why not red-flag THOSE ingredients as well,
    why target THIS one only?

  • someone11111

    BUMMER!! ARE YOU KIDDING ME?  this is in almost all dog foods…..what?
    now, what would be symptoms a dog has had too much sodium selenite?Would such symptoms be similar to a salt overdose?Does a dog’s natural electrolyte balance even out such imbalances on it’s own?