Originally Answered: [Sticky] Hyperthyroid cat that cannot be on thyroid meds and not ideal candidate for radioactive iodine treatment. What should I do?
I am not a veterinarian. I am an owner of multiple cats. In the last 2 yrs I've had 4 cats with hyperthyroidism. I have had 2 vets blindly attribute this to age, rather than trying to find the source of the problem. I don't believe that this trend is coincidence. I strongly believe that this 'trend' is largely due to a common toxic pet food ingredient called sodium selenite. I have no proof of exactly which pet food companies added this ingredient, nor exactly when they started adding it. I did, however, find information that indicates that sometime in 2016, AAFCO changed minimum pet food requirements with regard to sodium and selenium levels. Many petfood companies are fulfilling that requirement with a toxic inorganic source of selenium called sodium selenite. Below is some information that I found on sodium selenite:
--It may be toxic to blood, kidneys, liver, skin, central nervous system
--Is Selenium Toxicity a Concern for Our Pets?
Is raw selenite safe for cats?
-Damage to the liver and spleen in animals has also been observed, according to The National Institute for Occupational Safety and Health (NIOSH). According to the 1986 edition of the Handbook of the Toxicology of Metals, daily intake of about one milligram of selenium as selenite can be toxic.Aug 24, 2011
-The EPA (reminder: the EPA sets NOAEL – No Observed Adverse Effect Level – based on very detailed reviews of numerous studies) determined the highest allowable daily intake of selenium (for a 121 pound human, but based on animal studies) to be 0.853 milligrams per day.
-The American Association of Feed Control Officials (AAFCO) has determined an adult maintenance dog food can have a maximum of 0.57 milligrams per day (based on recommended daily calorie intake, not body weight);
-AAFCO has no maximum level of selenium established for cat food within their pet food regulations.
--Beware: Sodium selenite in pet food is toxic
...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.
--Role of Selenium in Pets Health and Nutrition: A Review
Research (Fan and Kizer, 1990; Olson, 1986) proved that inorganic selenium sources can be toxic in high doses; affecting an animal’s blood, liver and muscles. Inorganic selenium cannot be fully metabolized or stored in the body. Consequently, selenium deficiencies still arise in animals that are supplemented with inorganic selenium (Lopez et al., 1969).
Selenium concentrations in pet foods is highly variable.
However because inorganic selenium cannot be stored in the body, organic forms of selenium are being increasingly used as they are safer and more efficiently used in the body.
The role of trace mineral selenium in animals particularly pets is discussed and reviewed. Selenium deficiency is found to be one of the key factor behind many diseases like Kashin beck disease, cardiomyopathy, etc., Selenium levels and its forms in the diets play an important role in managing the trace mineral level in the body of the pet animal. However, toxicity associated with the high dose of selenium makes it vulnerable to pets and other animals due to the narrow difference between its required dose and the toxic dose. Current selenium supplements are mainly dependent on inorganic sources like sodium selenite which are found to be less bioavailable and also toxic. However, relative uses of selenium and its forms would be dependent on its nature of application and end use requirement. Keeping safety of the pet animals and environment as main focus areas, organoselenium compounds would be a good and alternate prospective choices for research scientists working in pet animal nutrition.
--[###### This announcement below indicates the likely timeframe when other pet food companies started adding sodium selenite to cat food. This makes sense to me in that before this timeframe none of my cats--even aging ones--were having any hyperthyroidism issues.######]
ADDITIONAL INGREDIENT ADDED TO OUR HUMAN GRADE PET FOODS
[The Honest Kitchen] August 14, 2016
Equipped with the above info, I now ensure that my cat food does not contain sodium selenite.
I also had a cat that had CKD, so I also stay away from foods with high phosphorus levels.
(You can find food lists for that here: Tanya's Comprehensive Guide to Feline Chronic Kidney Disease https://www.felinecrf.org/