By Jean Hofve, DVM

According to a report by the Environmental Working Group, excessive amounts of fluoride were found in 8 major national brands of dog and puppy food. The foods contained fluoride at levels between 1.6 and 2.5 times higher than the U.S. Environmental Protection Agency’s maximum legal dose in drinking water. These amounts were also higher than those associated with bone cancer in young boys in a 2006 study by Harvard scientists (Bassin 2006). Scientists have not studied the safety of high doses of fluoride for dogs, and fluoride is not listed as a necessary ingredient in pet food under the nutrient standards set by the Association of American Feed Control Officials (AAFCO).

According to the report, fluoride occurs naturally in the earth’s crust, rocks, and soil, and in some water supplies. But two-thirds of Americans — and their pets and livestock — are exposed to the chemical via tap water that is artificially fluoridated in an effort to prevent tooth decay (CDC 2006). The fluorine atom is also common in many drugs, such as Prozac, and other substances such as freon and teflon. High levels of drug and other residues have been found in groundwater, which may be directly consumed by livestock.

Ingestion of fluoride appears to cause gastrointestinal upsets at relatively low levels. Consumption of excess fluoride over long periods can cause accumulation of fluoride in the bones, a condition known as skeletal fluorosis. This may result in weakening of the bones (as calcium atoms are replaced by fluoride) and increased fractures, as well as bone cancer (osteosarcoma). It may also cause irritable-bowel symptoms and joint pain. Fluoride is a suspect in certain types of kidney and liver damage and possibly hypothyroidism.

The 8 high-fluoride brands tested by EWG’s lab contained ingredients that include chicken by-product meal, poultry by-product meal, chicken meal, beef and bone meal. Large breed puppy and adult dog foods contained some of the highest fluoride levels. Large breed dogs are extremely susceptible to bone problems, including osteosarcoma; some research ties fluoride levels to these conditions.

Chicken meal and the other cited ingredients are very common in dry cat food as well as dog food. Even natural and super-premium foods often contain chicken meal. Cats are far more sensitive to a wide variety of chemicals than other species. Levels of fluoride in cat food have not been studied, nor have the potential effects of long-term ingestion of excess fluoride. In other words, we have no idea whether fluoride in cat food is a problem or what kind of problem it may be. However, because the rendered ingredients found to be problematic in dog food are also found in cat food, it is an area that needs research to be done.

The Pet Food Institute (PFI)  released a statement about the EWG report: “The EWG report makes a scientifically invalid extrapolation on the safe consumption level of fluoride for dogs based upon the established level for the water that people drink.  The report contains no new research data beyond the cited pet food test results and it ignores a key fact: the biology of humans is very different from the biology of dogs.” It goes on to discuss several studies showing species differences in sensitivity to fluoride, without providing the actual references or disclosing essential details such as how long the studies ran. Their response ignores the typical situation where a dog or cat would eat the same food for many years, and does not address the potential chronic effects of such exposure. It would have been nice to hear something from PFI like “This is an interesting report, and although we feel that this is not a real danger to our pets, more research is clearly needed.” Instead, the smug, dismissive tone of their press release just reminds us that real science is not high on the list of these well-paid political lobbyists.

Little Big Cat does not recommend feeding dry food to cats for many reasons; and this is just one more. On the other hand, the fresh, non-rendered ingredients found in canned and raw diets are not currently considered to pose this risk. High-moisture, high-protein, low-carbohydrate diets (such as canned, raw, and homemade) are the most appropriate for cats.