By Cat, Jan 30, 2018 (photo of my cats, right, by Cat)
It is generally known that heavy metals are toxic; metals such as mercury, aluminum, cadmium, lead, arsenic and free-iron. There is a common ingredient present in most pet foods that can be very damaging to the health of your dog or cat, even though it is present in very minute amounts: sodium selenite (NaSeO3). It may be toxic to blood, kidneys, liver, skin, central nervous system of your pet.
Selenium is an essential mineral for most animals, but only when it is present in “organic” forms (meaning it is chelated by proteins or amino acids), such as that in selenium yeast (a form of nutritional yeast that has been grown on selenium). In “inorganic” forms which are typically salts (e.g., sodium selenite), it can be quite toxic, even in very small quantities. Also, as counter-intuitive as this sounds, it is a truth: the smaller the concentration of toxic selenium, the greater the harm because small concentrations mimic hormones, especially estrogen.
NOTE: If you take (or give to your pet) a multi-vitamin, multi-mineral, or specific mineral supplement that contains sodium selenite, stop using it and find a safer brand. For example, a widely used supplement that contains this toxic ingredient is Centrum.
See also: Miscellaneous & Information Menu (scroll down to “Pets”) on my Cat’s Kitchen blog.
Sodium selenite toxicity
Science Lab is a company that provides Material Safety Data Sheets (MSDS) about potentially toxic substances for humans, but is also applicable to other animals including our pets. Here’s what they have to say about sodium selenite (scroll to section 3 of the report (2). Note that I have put part of the text in bold for emphasis:
“Sodium selenite… may be toxic to blood, kidneys, liver, skin, central nervous system. Repeated or prolonged exposure to the substance can produce target organs damage. Repeated exposure to a highly toxic material may produce general deterioration of health by an accumulation in one or many human organs.” (1,2)
I feed kibble to my cats, but use only those brands that do not contain grains or soy which are known to be problematic for obligatory carnivores like cats. I just checked the two brands I am currently using and was shocked to see they both contain sodium selenite. I will no longer buy those brands. One of my cats, Charlie, has kidney issues according to blood tests, and my other cat, Chloe is also showing signs of the same trouble; both cats are overly-warm in the kidney area (just above the hip), indicating inflammation. They also drink lots of water and pee a lot.
NOTE: You have to read the small print in the ingredients section of the pet food, and look toward the end of the list. Here’s the list from one of the brands I had been using; I put the sodium selenite in red; note that it does not include one of the safer forms: selenium yeast:
Trout, ocean fish meal, sweet potatoes, potatoes, pea protein, potato protein, canola oil, smoked salmon, natural flavor, choline chloride, DL-methionine, taurine, dried chicory root, tomatoes, blueberries, raspberries, yucca schidigera extract, dried Lactobacillus acidophilus fermentation product, dried Bifidobacterium animalis fermentation product, zinc proteinate, vitamin E supplement, niacin, manganese proteinate, copper proteinate, zinc sulfate, manganese sulfate, copper sulfate, thiamine mononitrate (vitamin B1), vitamin A supplement, biotin, potassium iodide, calcium pantothenate, riboflavin (vitamin B2), pyridoxine hydrochloride (vitamin B6), vitamin B12 supplement, manganous oxide, sodium selenite, vitamin D supplement, folic acid.
A better way to provide essential selenium in pet food is to add an organic form of selenium; selenium yeast is one of the least expensive, similar in cost to the toxic sodium selenite. The Truth About Pet Food (1) is quoting from a scientific study (3). Note that “Se” is the chemical symbol for selenium:
The simple solution, as recent science has proven, seems to be adding non-toxic selenium yeast to animal feeds including pet foods. “Of about one dozen supplementation studies, none has shown evidence of toxicity even up to an intake level of 800 microg Se/d over a period of years. It is concluded that Se-yeast from reputable manufacturers is adequately characterised, of reproducible quality, and that there is no evidence of toxicity even at levels far above the EC tolerable upper intake level of 300 microg/d.” (1,3)
I have written to the manufacturers of the food I’ve been using, asking them to replace sodium selenite with Se-yeast. I will note that I have stopped using their products that contain this toxic heavy metal in the sodium selenite form. I’ve since learned that while the safer form (selenium-yeast) can be added to dog foods, it cannot be added to cat food per regulations from the AAFCO (Association of American Feed Control Officials) regulatory body for commercial pet foods.
I have found two brands of kibble that do not include any form of selenium: Acana and Orijen; their kibble is much more expensive than what I had been using, but well worth it for the betterment of my cats’ health. I also feed them raw cat food (thawed from the frozen state), which is naturally free of the toxic form of selenium, but it is also quite expensive.
The main diet for my cats is canned paté-style food that is selenite-free, because it is more affordable. I’ve found two brands at my local grocer that are selenite-free: Friskies and Fancy Feast canned food. (NOTE: not all of Friskies canned foods are selenite free, so read the label!). Because these foods contain no form of selenium, I add a sprinkling of Nutritional Yeast that contains Se-yeast to each serving of canned food.
Cat health update, April 28, 2018
After 2 months on sodium-selenite-free cat food, by beloved kitties are showing signs of improvement. Inflammation in their kidney area is much less (not as warm); however both still drink water almost constantly and consequently pee a LOT.
Safe Brands of Pet Food
The following lists are from Best Cat Food for Cats: (4) Note that I have crossed out those whose formulas have changed (due to action by the AAFCO) since the referenced article was published.
Wet or dry brands that do not contain sodium selenite:
- BFF (Best Feline Friend) – All canned and Oh My Hydration pouches.
- Fancy Feast
- Feline Natural
- First Mate
- Friskies – Tasty Treasures line [and certain other canned food]
- Fromm – four-star canned.
- Fussie Cat – canned.
- Hill’s Science Diet – most canned.
- Nature’s Logic – canned and dry.
- Soulistic – Pate & Shreds, and Original canned.
- Tiki Cat – all the Grill canned foods. Some Luau.
- Ziwipeak – canned
Dry-only brands that do not contain sodium selenite:
- Royal Canin – Aroma Selective dry.
Brands that contain the safer form (selenite yeast): (4)
- Farmina dry (US formulas) [Cat’s note: Be aware they may also change their formula to use sodium selenite, similar to Nutro and Ziwipeak, as indicated below,, due to action by the AAFCO]
Nutro (Hairball Control and High Protein dry only) Edit: Nutro changed their formulas. Used to be all dry formulas contained selenium yeast. Now only two dry foods have it. [Cat’s note: 3/13/18 update: Nutro has replaced the safe selenium yeast with the toxic sodium selenite per email reply from them. I believe this is because they are required by AAFCO* to do so. Ziwipeak (canned or air-dried)[Cat’s note: per their website: canned contain no selenium at all; all air-dried contain sodium selenite, not Se-yeast. I sent them an email requesting confirmation. Their response is that their canned and kibble dog foods use se-yeast, but that form is currently not allowed in cat food by AAFCO* regulations.]
‘* AAFCO is Association of American Feed Control Officials. My take is that they should still remove the sodium selenite.