Is Selenium Toxicity a Concern for Our Pets?

Selenium is an essential (trace) mineral required in our pets diet.  The most common form of delivering the required selenium in pet food is the supplement ingredient sodium selenite.  Is sodium selenite safe for our pets?  Further, is selenium toxicity sickening our pets?

Mercola.com recently posted an article warning human consumers of the potential risks of some multi-vitamins that contain sodium selenite.   The Mercola.com article states “both sodium selenite and sodium selenate are classified as “Highly Toxic”, based on oral administration trials using rabbits and rats.”

“Studies have shown that:
•    Long-term exposure to selenium, sodium selenite, sodium selenate, or selenium dioxide may cause paleness, coated tongue, stomach disorders, nervousness, metallic taste and a garlic odor of the breath. 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.
•    In one study, sodium selenite was found to induce substantial DNA damage in human fibroblasts.
•    More recent research also indicates that too much selenium may contribute to the onset of diabetes.”

Ok…with pet food…

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.  AAFCO has established a minimum requirement of selenium for both cat food and dog food at 0.03 milligram per day (again, based on recommended daily calorie intake).

EPA – maximum 0.853 mg per day for a 121 pound human.
AAFCO – maximum for dog food 0.57 mg per day – maximum for cat food none, based on recommended daily calorie intake.

It needs to be emphasized that EPA recommendations for maximum intake of selenium are based on mg per kg of body weight (I converted kg of body weight to pounds above).  AAFCO recommendations for maximum intake of selenium for dogs (no maximum for cats) based on calorie intake (oh, by the way – AAFCO still hasn’t decided on requiring calorie information on pet food labels yet).

So, lets say a pet consumes the exact recommended calorie intake, a 30 pound dog would be consuming 0.57 mg of selenium (regardless of the type of selenium supplement) per day.  According to EPA’s maximum a 30 pound dog should be consuming only 0.21 mg per day (regardless of calorie intake) to be within the No Adverse Effects level.

EPA – (based on human maximum) 0.21 mg per day for a 30 pound dog.
AAFCO – 0.57 maximum per day for all size dogs; no maximum established for cats.

Setting the EPA/AAFCO maximum and/or lack of maximum levels aside for a moment, here is some more to think about regarding selenium…

Some pet food manufacturers utilize ingredients that naturally provide the needed selenium such as organ meats, seafood, and plants.  Some pet food manufacturers provide the needed selenium to a pet diet with the use of selenium yeast.  (Selenium yeast can be a safer form of to deliver the required selenium to a pet diet; according to one study Sodium Selenite is “2.94 times more toxic than Selenium Yeast”.  But, sadly, the FDA has not yet approved the use of selenium yeast for use in cat food – only dog food has FDA approval.)  Most pet food manufacturers provided the needed selenium yeast to a pet diet by use of sodium selenite.  And by the way, some of those same pet foods that add the potentially risky sodium selenite supplement also contain internal organs by use of by-product, by-product meals, and grains.  By-product ingredients – by definition – include numerous internal organs — internal organs are one of the food sources of selenium.  Grains as well can be a food source of selenium.  So, not only are some foods adding a selenium supplement, some of these same foods contain a variety of ingredients rich in selenium content.

As well, selenium content in various foods can vary greatly depending on the soil the food was grown in (grains, vegetables) and depending on the selenium content of the feed the livestock animal (cattle, poultry) was fed.

A pet food manufacturer would actually need to test each and every ingredient (almost) of each and every batch of pet food for selenium content and then only add the remaining needed selenium supplement to the pet food in order to assure the pet is not consuming high levels of selenium.  What is your guess as to how many pet food manufacturers do this?  (Mine too!)

How would we know if our pets are suffering from selenium toxicity?

According to the Oregon State University Linus Pauling Institute Micronutrient Research for Optimum Health Information Center “The most frequently reported symptoms of selenosis (selenium toxicity) are hair and nail brittleness and loss.”  Again, for humans.  But…

What is a common complaint of pet owners regarding their pets?  Shedding.  Hair loss.

“Other symptoms may include gastrointestinal disturbances, skin rashes, a garlic breath odor, fatigue, irritability, and nervous system abnormalities.”  Besides the garlic breath odor, all symptoms that could be frequently seen in pets.

From Molecular, Clinical and Environmental Toxicology: Volume 2: Clinical Toxicology “In acute selenosis (in animals), selenium accumulates in and causes damage to heart, liver and kidneys.”

If your pet has unexplained gastrointestinal concerns or excessive shedding, don’t hesitate to ask your veterinarian to test your pet for selenosis.  Should you test your pet for selenosis and they test positive, PLEASE report these test results to the FDA and your State Department of Agriculture.  As well, for those that might test a pet food for answers to questions of a sick or dead pet, you might want to consider testing the food for selenium content too.  Should you test a pet food for selenium content  and the pet food tests high, report your findings to the FDA and your State Department of Agriculture.

If the pet food you trust uses the supplement sodium selenite, ask the manufacturer to consider using selenium yeast instead.  For cat owners, please ask your pet food manufacturer to contact the FDA/CVM and ask for them to approve the use of selenium yeast in cat food.  It wouldn’t hurt for cat owners to write the FDA/CVM and ask them to approve this ingredient too.  Also cat owners, please contact your State Department of Agriculture (ask for the person in charge of pet food) and request that maximum levels of selenium in cat foods be established.

Don’t hesitate to ask your pet food manufacturer if they test for selenium content of the pet food, and how often they test; don’t hesitate to ask to see these test results too.

Wishing you and your pet(s) the best,

Susan Thixton
Pet Food Safety Advocate
Author, Buyer Beware
Co-Author Dinner PAWsible
TruthaboutPetFood.com
PetsumerReport.com

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