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Thomas Dock, CVJ, Vet. Technician  
Male, 49
Indianapolis, IN

Interests: animals, Reading (sci-fi and fantasy)
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Preservatives Cause Cancer??  Probably not...

Jul 02, 2009 - 12 comments
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pet food preservatives cancer

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pet food

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preservatives



Another pet food myth that continues to abound is that the presence of certain preservatives causes cancer in our pets.   This tall tale has been around since I first started working in the pet industry way back in the late 1980s!  The controversy centers on three compounds, BHA, BHT, and ethoxyquin.

I recall hearing how the preservative, ethoxyquin, had been implicated by dog owners as causing allergic reactions, skin problems and, of course, cancer.   There was little to no scientific evidence to support these claims, yet any pet food manufacturer who utilized ethoxyquin was often shunned.   I distinctly remember this because the store I worked for sold Iams and Eukanuba products as our sole food.  (This was back before Iams was purchased by Procter and Gamble).

Ethoxyquin has been added to pet foods and animal feeds for more than 35 years.  It is very useful to help stabilize and protect fats and oils during the high temperatures needed to cook and extrude many pet foods.  Without good preservation, the fats will go rancid causing the food to lose calories and certain fat soluble vitamins.  The FDA did allow up to 150 parts per million(ppm) of ethoxyquin in pets foods but has asked pet food manufacturers to reduce that to less than 75 ppm.   It is a rare pet food that exceeds the 75 ppm level.  

BHA and BHT (butylated hydroxyanisole and butylated hydroxytoluene) are two other preservatives that get a lot of bad press despite the fact that a good percentage of us eat these almost every day.  These preservatives can be found in our butter, cereals, baked goods, snack foods, and even my precious beer!   Both of these compounds keep fats from becoming rancid, thus protecting the food.  The FDA allows up to 200 ppm of the fat or oil content of the food of BHA or BHT.  Opponents of BHA/BHT often quote a study in rats in which BHA caused cancer of the forestomach in rats.   Since we don’t have a forestomach, the conclusions that BHA will cause cancer in us are not perfectly valid.  Furthermore, the FDA has said that we would need to ingest 125-150 times as much BHA as most people currently do in order for it to potentially cause any problems.  So, while the FDA does admit that these products need more research, they are generally regarded as safe (GRAS) in the levels currently found in our foods.   Pet foods use much lower levels.

I think the more telling argument for me is “why would a pet food company purposefully add something known to cause cancer to their food?”  Surely, all of these companies have intelligent, well paid attorneys who will remind them that the American consumer is savvy and won’t tolerate this kind of deliberate alteration of their pet’s food.

Now, other preservatives are being used in ever-increasing amounts.   Vitamin E, citric acid and mixed tocopherols are considered to be a more “natural” solution to the preservative issue.  There is some concern over shelf life of foods preserved this way.

My final point is to also toss the ball back into the court of individuals who originally propagated their version of issues with BHA, BHT, and ethoxyquin.  Did anyone ever look at the breeds and lineages of the pets who were cancer-stricken?   Was there a potential for a genetic component or even a family sensitivity to these compounds?


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by zodiacqueen, Jul 02, 2009
If preservatives do not cause cancer, then please explain why so many dogs and cats get stricken with cancer.  Our pets' cancer rates are MUCH higher than humans.  There IS a reason for this.  I do not think that genetics is the only answer, either.

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by Thomas Dock, CVJ, Vet. TechnicianBlank, Jul 02, 2009
That's a good question zodiacqueen...one that I don't have a good answer to.  BUT..consider the fact that breeds like Goldens and Boxers are much more prone to cancer than other dogs.   I think you would have to agree that genetics plays a pretty big part in the development of cancer in our pets.  Genetics is not the only answer, but it can have a pretty profound effect!

And please note, I did say that these compounds CAN cause cancer, in laboratory animals and at extremely high dosages.  If BHA and BHT were significantly carcinogenic, we would probably see similar cancer rates in pets and people as both of our diets contain BHA and BHT.  From what I have read, levels of BHA and BHT are MUCH lower in pet foods than in the foods we eat routinely.

I think the answers lie somewhere in the levels of these compounds needed to provide the antioxidant effects.   As some ancient person (Aristotle?) once said, the difference between a medicine and poison is the dose.

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by Tammy2009, Jul 02, 2009
Answer for that zodiacqueen:  inbreeding, there is no survival of fittest.  We want 2Ib yorkies, so the smallest runts are breed together.  Dogs are bred for looks or particular traits, not always the healthiest animals.  

A interesting point would be comparing the cancer rates in dogs to cats, since cats eat similarly processed food but are not bred in the same way for looks (not comparing the full bred cats like siamese, bengals and such).  

I REALLY like that quote Thomas.  

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by ginger899, Jul 02, 2009
I don't think cancer is just a food issue, or a 'what we or our pets put in our mouths' issue. Basically the development of a cancer is because the immune system did not do its job at the moment a mutant cell started dividing (which can happen more regularly, in all of us, than we think!) Usually the immune system, unnoticed by us, does its job. Anything which weakens the system to some 'tipping point' could cause cancer to develop. Whole lifestyles have to be examined. That goes for dogs or other pets, as well as people.

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by jedmu, Jul 03, 2009
JEDMU
As a human, I take 250mg of BHT everyday since 1983 after reading several books on Life Exrension. I agree with Thomas
that the rat study was flawed as the human anatomy is not the same.Rancid oils have a serious long term effect on
humans & you're pets health.Oil starts to become rancid as soon as you open it and needs to be proteted with BHT.
I am 68 years old and in perfect health. 250mg of BHT is taken along with my daily vitamins & minerals.

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by LDK123, Jul 04, 2009
How about all the flea-dip and pest treatments they are subjected to as well and lawn chemicals?

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by Thomas Dock, CVJ, Vet. TechnicianBlank, Jul 04, 2009
LDK123:  Sounds like I should do a blog on that topic as well!!  Lots of controversy about the flea and tick topicals right now

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by Tammy2009, Jul 04, 2009
yes please about the flea and tick .... there have been a lot of bad rep on the particular brand (zodiac) that pet stores can sell.

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by JessOneill, Jan 20, 2010
Does BHA cause cancer in Dogs?

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by Thomas Dock, CVJ, Vet. TechnicianBlank, Jan 20, 2010
Hi Jess...to my knowledge, there is no evidence that BHA, at levels found in dog food (or in our own foods) causes cancer in dogs.


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by Piparskeggr, Jan 20, 2010
Counting our current 4; Anita and I have had (ourselves or in our younger lives) about 20 over the past 50 years or so, plus there have been at least another 40 or so owned by close family and friends.

I'd say the dog count is similar within a similar subset of families.

Everyone I know uses commercially prepared pet foods.

No cancer.

Most of the pets have lived above average life spans...balanced diets, preventative vet visits (including recommended vaccines), enriched habitats, and a caring/loving attitutde towards these furry members of the family...

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by oscarguy, Feb 25, 2011
Dr. Denham Harman did a lot of research tests using mice dosed with BHT and achieved an average lifespan increase of 40% to 50% in the mice dosed with BHT. He is the originator of the free radicals concept of aging. His critics argued that all he was doing was eliminating cancer in the BHT dosed mice and that accounted for the increased lifespan average. If that is ALL he did I think it is something VERY important.   ...Oscar

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