1999 Letter to Dog Group re: Fluoride in Dog Food and Osteosarcoma

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1999 Letter to Dog Group re: Fluoride in Dog Food and Osteosarcoma

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Someone asked for info on fluoride in dog food. Here is a letter written 22 years ago to a large dog club in the US.
For a more recent article, please see the EWG report from 2009.

EWG: Dog Food Comparison Shows High Fluoride Levels
https://www.ewg.org/research/dog-food-c ... ide-levels


September 17, 1999

Subject: Re: Hypothyroidism in Dogs

Hello all,

I am writing to share information obtained while researching hypothyroidism and fluoride poisoning.

I have come across several websites which reported that hypothyroidism is THE major health concern among dog owners and breeders. I would like to make you aware of the role of fluorides as a cause of hypothyroidism.

Many people are not aware that fluorides were at one time given as _effective_ anti-thyroid medication to hyperthyroid patients, specifically to reduce thyroid activity (1a,b,c,d,e). Doses ranged from 0.9 to 4.5 mg a day, obviously much less than is consumed by a dog (or humans!) every day.

Many dog foods contain extremely high amounts of fluoride.

Studies report a "low" fluoride content as 55 or 56 ppm (or mg/kg), high as 460 ppm (mg/kg).(2,3)

In 1980 Thompson et al (4) reported that the phosphate industry, along with university researchers and the Association of American Feed Control Officials (AAFCO), set up standards for safe levels of fluoride in feed phosphates. A P to F ratio of 100:1 was adopted in 1952 for any product sold to the feed industry as "defluorinated phosphate." This level was considered "safe", although plenty of research already existed at the time documenting the toxic effects of F-. Thompson further writes that this level was still considered safe by the industry in 1980, which is simply outrageous considering the overwhelming amount of literature available with evidence to the contrary, on animals as well as humans.

According to Thompson, "industry has the technology to produce feed phosphates of lower fluoride content; however, there is an increased cost in further reducing fluoride content"...


Studies exist which claim to supply evidence that fluorides are not responsible for certain health effects in dogs. This is simply shoddy science. For example, studies were undertaken in Allegan County, Michigan, as part of an investigation of reproductive problems in Shetland sheepdogs (shelties). In 1980 the authors, Marks et al. (2), wrote that since 1970, at least 115 sheltie litters at this kennel had been grossly deformed and/or had died, generally within 3 days of birth. The causative factor(s) appeared to be associated with the environment, as the shelties had had successful pregnancies elsewhere. There was some concern that a potential threat to human reproduction also might exist in this area. It was discovered that fluoride in the dog food had caused mottled teeth and bony exostoses in dogs at this and at least two other kennels. The authors undertook a project in which they fed the dog food to rats (!) to determine the reproduction toxicity of fluoride. They fed groups the dog food containing either high (460 ppm) or low fluoride (56 ppm), later concluding that fluorides made no difference and only showed dental fluorosis and no other health effects, but they never indicated that they looked for any, and how. They further stated that rats cannot be used in the search for the cause(s) of reproductive problems in dogs in this kennel, something which should have been obvious from the start. At no time was a control group used, which had NO fluoride in the diet. [For your info, impaired thyroid function in rats has already been documented at 1 ppm!(5)]

The same authors undertook another study in 1990 (1b), this time funded by Uptown's pharmacological research department, where almost identical doses were used, but not a NO fluoride investigation. This time, although some abnormalities could clearly be observed, again the authors claimed that fluorides were not the cause. In 1994 Marks released yet another paper, discussing voltage abnormalities as the possible cause (1c)...

The toxicity of fluoride in reproduction has been documented many times in animal studies (6,7,8,9) as well as in humans.(10,11)

Here in Canada, government information on animals such as sheep and their mineral requirements clearly mark fluorides as the cause of mottled teeth, dry hair, lameness, and _ poor reproduction_. (12)

The fact that some dog foods can also contain high amounts of iodine, together with high fluoride content(13), poses an additional threat to the thyroid gland (14).

Utmost disturbing is the fact that fluorides continue to be promoted as an "essential nutrient" in animal feed when no such evidence exists. The FDA considers fluoride as an "unapproved" new drug, yet does nothing to address the high amount of fluoride in animal feed, the regulation of which is part of its mandate. The Salt Institute writes that fluoride in animal feed is needed for growth and anemia prevention. (15) That exactly the opposite has been demonstrated in cattle studies seems of no concern. Hillman et al.(16) showed that cattle afflicted with fluorosis developed hypothyroidism, anemia, and eosinophilia of leukocytes. Already in 1934 studies done by Chang et al. on the effects of mixing fluorine-containing phosphate in cowfeed showed comparable data.(17) Many more studies can be found within the last 80 years.

We have compiled over 150 symptoms and associations of hypothyroidism, all of which directly correlate with symptoms/associations found in literature documenting fluoride poisoning, at:

COMPARISON OF SYMPTOMS: FLUORIDE POISONING/HYPOTHYROIDISM [https://poisonfluoride.com/pfpc/html/symptoms.html]

We urge you to consider the role of fluorides in hypothyroidism in dogs and hereby hope that pressure will be applied by you and other similar groups in getting the FDA and AAFCO to re-evaluate the incredible fraudulent standards set for fluorides in animal feed.


In 1998 Langenbach reviewed 169 cases of osteosarcomas on dogs.(18)

Senior Toxicologist William Marcus of the EPA states that fluorides are the only compound known - including radioactive compounds - to induce osteosarcomas in rodents.(19)

In 1996 the New Jersey Department of Health discovered a 6.9 increase in osteosarcomas in young males who live in a fluoridated area.(20)


1a) Galetti, PM;Joyet, G - "Effect of Fluorine On Thyroidal Iodine Metabolism in Hyperthyroidism" J Clin Endocrinol 18:1102-1110 (1958)

b) Gorlitzer von Mundy - "Einfluss von Fluor und Jod auf den Stoffwechsel, insbesondere auf die SchilddrŸse" MŸnch Med Wochenschrift 105:234-247 (1963)

c) Gordonoff, T. - Fluor und die SchilddrŸse, Toxikology des Fluors Basel/Stuttgart (1964)

d) May, W - "Antagonismus zwischen Jod und Fluor im Organismus" Klin Wochenschr 14:790-792 (1935)

e) May, W - "Behandlung der Hypothyreosen einschlie§lich des schweren genuinen Morbus Basedow mit Fluor" Klin Wochenschr 16:562-564 (1937)

2) Marks TA, Schellenberg D, Metzler CM, Oostveen J, Morey MJ - "Effect of dog food containing 460 ppm fluoride on rat reproduction"J Toxicol Environ Health 14(5-6):707-14 (1984)

3) Schellenberg D, Marks TA, Metzler CM, Oostveen JA, Morey MJ -"Lack of effect of fluoride on reproductive performance and development in Shetland sheepdogs" Vet Hum Toxicol 32(4):309-14 (1990) Published erratum appears in Vet Hum Toxicol 32(6):527 (1990) Pharmaceutical Research and Development, Upjohn Company, Kalamazoo, MI.

4) Thompson DJ - "Industrial considerations related to fluoride toxicity" J Anim Sci 51(3):767-72 (1980)

5) Bobek S, Kahl S, Ewy Z -"Effect of Long Term Fluoride Administration on Thyroid Hormone Levels in Rats" Endocrinol Exp (Bratisl)10:289-295 (1976)

6) Maylin GA, Eckerlin RH, Krook L - "Fluoride intoxication in dairy calves." Cornell Vet 77(1):84-98(1987)

7) Hoffman DJ, Pattee OH, Wiemeyer SN - "Effects of fluoride on screech owl reproduction: teratological evaluation, growth, and blood chemistry in hatchlings."Toxicol Lett 26(1):19-24 (1985)

8) Eckerlin RH, Krook L, Maylin GA, Carmichael D - "Toxic effects of food-borne fluoride in silver foxes" Cornell Vet 1986 Oct;76(4):395-402

9) Schultheiss WA, Godley GA - "Chronic fluorosis in cattle due to the ingestion of a commercial lick" J S Afr Vet Assoc 66(2):83-4 (1995)

10) Tomas James Rees - The Toxicology of Male Reproduction, Literature Review in Applied Toxicology, Portsmouth University, February 1993

11) Susheela AK, Jethanandani P -"Circulating Testosterone Levels is skeletal Fluorosis patients" J Tox Clin Tox 34(2):187-189 (1996)

12) Ontario Ministry of Agriculture, Food and Rural Affairs http://www.gov.on.ca/OMAFRA/english/liv ... nernut.htm

13) Mumma RO, Rashid KA, Shane BS, Scarlett-Kranz JM, Hotchkiss JH, Eckerlin RH, Maylin GA, Lee CY, Rutzke M, Gutenmann WH, et al - "Toxic and protective constituents in pet foods" Am J Vet Res 47(7):1633-7 (1986)

14) Zhao W, Zhu H, Yu Z, Aoki K, Misumi J, Zhang X -"Long-term Effects of Various Iodine and Fluorine Doses on the Thyroid and Fluorosis in Mice" Endocr Regul 32(2):63-70 (1998)

15) Salt Institute: Salt and Trace Minerals in Animal Nutrition and Agriculture http://www.saltinstitute.org/25.html
Animal feed is a major market for salt. In the 1998 calendar year revenue was $86,684,000 for 1,739 tons supplied. Salt used for water conditioning amounted to a sales income of $285,642,000 for 2,986 tons.

16) Hillman D, Bolenbaugh DL, Convey EM - "Hypothyroidism and anemia related to fluoride in dairy cattle" J Dairy Sci Mar;62(3):416-23 (1979)

17) Chang CY, Phillips PH, Hart EB - "The Effect Of Feeding Raw Rock Phosphate On The Fluorine Content Of The Organs And Tissues Of Dairy Cows" J Dairy Science 17:695-700 (1934)

18) Langenbach A, et al.- "Extraskeletal osteosarcomas in dogs: a retrospective study of 169 cases (1986-1996)." J Am Anim Hosp Assoc. 34(2):113-20 (1998)

19) Marcus WL - "Facts for Fluoridationists", Earth Island Journal Special Report:Fluorides And The Environment (1998) see also: Letter By William L. Marcus, Ph.D (1995) http://www.rvi.net/~fluoride/marcus.htm

20) Cohn PD -"A brief report on the association of drinking water fluoridation and the incidence of osteosarcoma among young males" New Jersey Department of Health (1992).
Last edited by pfpcnews on Mon Apr 18, 2022 6:06 pm, edited 5 times in total.
Posts: 1015
Joined: Mon Apr 03, 2006 5:50 am

2009 Article by the EWG on fluoride in dog food.

Post by pfpcnews »

2009 Article by the EWG on fluoride in dog food.

Dog Food Comparison Shows High Fluoride Levels
https://www.ewg.org/research/dog-food-c ... ide-levels
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