I always love checking out labels and looking into the ingredients of dog products that go in or on our pets. Recently, I’ve been looking at dog dental products, as there seems to be a rash of slick marketing campaigns aimed at our pet’s teeth. You are probably being bombarded with “use this treat” or “add this to their water” on a regular basis – if you don’t, surely you don’t love or care for your pet enough.

But what is in this green goop or blue chew stick anyway? Recently I examined an ingredient in a dog dental water additive that had a couple of questionable ingredients.

Today we’re looking at Sodium Hexametaphosphate, an ingredient that is being used in pet products including dental treats and food. This ingredient is the active ingredient of a new pet dental stick currently making the rounds on pet blogs. Sodium Hexametaphosphate is being marketed as a benefit, said to reduce tartar and plaque buildup. This additive is the active ingredient in many “dental care” kibbles on the market, and dental treats. So what is this active ingredient? Let’s look a bit further.

Do note I’m not a scientist, and I am researching scientific studies that are posted online and wrapping up that research in this post. Please refer to the studies I link here, or your own common sense, and draw your own conclusions about what you want to feed your pet. This is my opinion only.

What is Sodium Hexametaphosphate, and does it belong in a dog treat?

Sodium Hexametaphosphate is an emulsifier, sequestering agent, and texturizer. It is used to prevent scale formation and corrosion, and to prevent the appearance of a product from changing. It is also known as Graham’s Salt, HMP, SHMP, a “polyphosphate salt”, and by several other names.

This chemical ingredient is used in all sorts of things, and is generally known as a food additive for many foods in your fridge and pantry. However, it is also used to treat water, in detergent, soap, metal plating, remove scale, to create polymers… and your dog’s dental treats.

According to BeFoodSmart.com and the Material Safety Data Sheet (MSDS) for sodium hexametaphosphate, it carries the following risks:

In animal studies, the following effects were reported: pale and swollen kidneys, increased kidney weights, bone decalcification, muscle fiber size changes, hyperplasia and severe skin irritations.

The chemical can be hazardous to humans if ingested, and slightly hazardous on contact. You can find out more about the health risks in this study, or the MSDS.

In foods that contain SHMP, DogFoodAdvisor.com advises visitors that the additive is “a man-made industrial polymer with no known nutritive value….we’re of the opinion that food is not the place for tartar control chemicals.” This is also echoed by veterinarian Dr. Marty Becker, who writes “Rather than roll the dice on a commercial “dental care” pet food or treat that won’t, by itself, keep your pet’s mouth healthy (and quite likely isn’t optimally nutritious), I recommend taking the following steps instead” and lists several other options, such as brushing, oral exams, and a raw diet (however, do be aware that bones can lead to bowel perforation and peritonitis in a small percentage of cases… like my dog Mort).

Long term chronic effects of consuming this chemical

While several sources state that long-term low dose of this substance causes cancer, I could not find a study to support this. In fact, I couldn’t find a substantial study that discussed or evaluated the long term consumption of this additive in humans or any other species, or the potential effects of bio-accumulation. However, according to this Material Safety Data Sheet, it’s a potential concern for this additive:

Substance accumulation, in the human body, may occur and may cause some concern following repeated or
long-term occupational exposure.

In long-term animal studies, inorganic polyphosphates produced growth inhibition, increased kidney weights, bone
decalcification, enlargement of the parathyroid gland, inorganic phosphate in the urine, focal necrosis of the
kidney and alterations of muscle fibre size. Inorganic phosphates have not been shown to cause cancer, genetic
damage or reproductive or developmental damage in animal tests.

Considering this passage, I’m incredibly concerned (for both us and the pets) about long-term consumption of this additive that’s essentially a polymer. The “longer term” studies noted seem to be in the 6 month range, which doesn’t seem overly comprehensive. I think it’s fairly safe to say I plan to avoid Sodium Hexametaphosphate going forward.

What about added color?

Some dental products also contain Titanium Dioxide, which also falls into a “not studied enough and potentially harmful when consumed” category. For more information on Titanium Dioxide, keep your eyes peeled for an upcoming article discussing this ingredient.

So is it safe or not?

With the “internet research” I performed I cannot say I feel that it is safe, or worth the risk. The study of long-term small doses, which could equal what’s in this product, does concern me due to the potential for bio-accumulation as noted in the MSDS. And for that reason, in addition to it being a chemical, the product would be a no-go for me personally.

So make sure you look past the marketing campaigns on pet blogs and make sure you read the labels and get a good idea of what you’re feeding your own dog. Don’t discredit small amounts or the weird-sounding ingredients near the end of the list. Be wary of marketing. At least this product isn’t being marketed as “natural” this time.

So that’s a thing… but does Sodium Hexametaphosphate even work in dental products?

In this study of this active ingredient’s effectiveness in squirrel monkeys, it was found to not help unless the teeth were pre-cleaned. It was found that:

At the end of 6 months, dental calculus did not differ significantly between the experimental groups. Therefore, we conclude that HMP is ineffective in squirrel monkeys with preexisting dental calculus.

So sodium Hexametaphosphate may be useless unless you perform a dental cleaning first

So then I found the study on dogs specifically. The study involved 27 Beagles who “received an initial dental prophylaxis” (a cleaning). So yes – this product might work, but only after you clean your dog’s teeth, and use these treats with these questionable ingredients regularly. If you don’t do that dental cleaning, studies show you’re probably wasting your money. But at any rate, your pet might be a science experiment if you choose to provide this unnatural additive for oral health.

About Author

Jen deHaan is graphic designer, small business owner, and dog person living in Bay Area, California. Jen enjoys learning about dog training and behavior, and has taken several courses and seminars since 2010. She also contributes articles to leading websites, such as Victoria Stilwell's Positively . It all started with a great dog called Mikey (aka "dude"), loved and lost but remembered forever. Jen also runs a freelance business focusing on graphic, web, and UI design at FoundPixel, and a small business creating hand crafted dog products at Stylish Canine.

  • Very informative Jen. Its wonderful that you help spread awareness about what goes into pet products. I think totally natural chews for a pet’s dental hygiene are neem sticks (tiny branches of the Neem Tree). I give these to both my dogs who love to chew on the stick, which then turns into a bristle (looks like a rope toy) and the neem juice that they end ingesting as a result of chewing the stick also help keep intestinal parasites at bay. Its great for oral hygiene as well as overall health of the pet. And every 2-3 days a week I brush their teeth with the Curry n Pepper neem tooth powder which is completely free of any additives, artificial sweetners or other chemicals found in most toothpastes.

    • Fantastic addition, Hetal! I love the treats and food you make, I should absolutely try your Neem tooth powder. Do you sell the sticks as well? I\’m looking for some high-quality natural products – Mort lost 2 teeth in an accident, and the teeth below the ones that came out are quite covered in tartar since he doesn\’t chew in that area of his mouth.

  • I liked this post because it is a reminder to take a closer look at the ingredients of any type of product our pets consume, whether it’s food, treats, supplements or water additives. I think you make some great points that products containing sodium Hexametaphosphate may not be worth the risk, because do the products actually make that much of a difference for the pet’s health? I doubt it.

    As you said, our best bet for helping our pets’ teeth is simply to brush the teeth, give them something appropriate to chew on, feed them raw or have their teeth professionally cleaned.

  • siful

    Thank you so much for your informative post. for this post we learn that we should keep in mind everything what we use/give to our pet.

  • DogFactThusiast

    This article is alarming. If you Google “adverse effects of water/protein/tea/organic food” or ANYTHING you will always get a few odd-ball studies that state something is bad for you. If you want to find accurate and relevant scientific information please read review articles where they summaries all the pertinent information about a subject.

    If you did your homework correctly you would find out the sodium hexametaphosphate is found in TOOTHPASTE. Because it is SAFE. It has been on the market for over 20 years in humans and has been completely safe so much so it is on the FDA “GRAS” label (generally redarded as safe) so your monkey reference is irrelevant.

    There have been numerous studies that prove that adding sHMP prevents plaque from turning into tartar and it affects the WHOLE mouth as opposed to chews which only act on the teeth your dog prefers using.

    Those side effects you mentioned are also inaccurate as they are side effects of EXCESSIVE phosphorus intake. A dog’s food is always completely balanced because it must meet state regulations. The phosphorus in the dental agent is included in the balanced diet so these problems with bone density and parathyroid gland enlargement are not valid points.

    Others should very much heed your disclaimer wherein you state that you are not a scientist because this blog has misleading and fear-mongering information.

    I hope your other articles are much better researched since it seems like you have a follower base that is happy to take anything you say as truth.


    • A few quick notes as it doesn’t appear like the article was read all that closely. First of all, the “monkey” study was regarding (and referenced on) efficacy in a particular usage, not safety. So yes it’s irrelevant to your point, but only because it’s on a completely different topic. I was not discussing safety in that section of the article, nor did I say that the product was ineffective. I actually said that it could be effective in a particular use case and was quoting both of those studies as to how the product should potentially be used (after a calculus cleaning). To be helpful if someone chooses to use it, but I suppose those points were missed (they were near the end).

      As for it being in human toothpaste for many years and on a GRAS list, I personally don’t take that as a reason for safety in dogs – I do seek specific studies. If we blindly accept GRAS ingredients as safe for dogs, so is fluoride, aluminum and other ingredients in toothpaste and other cosmetics that are widely scrutinized and considered by many to be unsafe regardless of “GRAS” status.

      Regarding safety, I said I simply did not have enough information due to the few short studies found to deem whether or not bioaccumulation could be an issue for dogs, because I searched for days and could not find any such study on long-term use. Basically the entire article is on the standpoint that I do not have enough information to deem whether or not it is safe for my own dogs, so until then I choose not to use it.

      I keep these comments open so other people can add any information that they wish to add. I do not think it’s effective fear-mongering or irresponsible in the least to put big disclaimers at the beginning of an article as I have, and leave my comments section open for input. And I have no links to the industry to incentivize me to write any of the above, for or against, only my own dogs’ health – I was simply searching for a safe product to use, and was considering one with this ingredient that led to research I felt may assist others doing the same. Anyway, regarding comments I do ask and hope that the comments left will also leave links to relevant studies, which I do not notice above. If you do have links to data to support the “odd ball” studies I linked were inaccurate (which are the only scientific studies I could find relevant to this ingredient, and a vet’s opinion – but perhaps there are new ones or ones that are difficult to find), I’m all ears as all I’m trying to do is figure out what to use and maybe help a few folks out on their own path.