A study by researchers at the University of Missouri finds that eating canned dog food may increase a pet’s exposure to the endocrine-disrupting chemical, Bisphenol A (BPA).
While the study was short-term, the results were “very revealing,” says investigator Dr. Cheryl Rosenfeld, an associate professor of biomedical sciences in the MU College of Veterinary Medicine. Fourteen healthy pets were switched from their usual diet of kibble to canned food. Could a two-week menu change raise the dogs’ BPA levels?
It did, three-fold, and that could really be an issue for dogs that eat the same diet every day.
Over 300 studies have linked BPA to health problems from reproductive disorders to cancer, and now research is shedding light on how people and animals are exposed to the plastic-hardening chemical. While the FDA has reviewed the studies, they still consider BPA “safe at the current levels occurring in foods.”
By measuring BPA’s escape from packaging, scientists are narrowing the focus. One study settled the debate over whether BPA—banned in baby bottles but used in many other items—seeps from metal can linings and taints human foods. (It does).
And in August, a long-term study in the UK found a sharp decline in canine fertility associated with exposure to other endocrine-disrupting chemicals. The researchers considered food packaging a possible source, finding the chemicals in a range of dry and wet foods.
Some plastic dog toys have also been found to leach the chemical. A study at Texas Tech by environmental toxicologists Phil Smith and Kimberly Wooten found that BPA and phthalates leached from plastic bumpers into dishes filled with artificial dog saliva.
Wooten, who wasn’t involved in the present study, says that while it isn’t clear if dog health is being harmed long-term, “it’s still important information to have since there’s so little data on canine exposure to these types of chemicals.” She knows of no other studies that have looked at the effects of a specific BPA source on the concentrations in the blood.
“I’d say a 3-fold increase suggests that for dogs that eat canned food, their diet is the most important contributor to their total BPA levels.”
The current study highlights another concern; with the pet food industry being held by about five companies, it seems commercial foods aren’t as diverse as packaging suggests. Of the two (unnamed) brands in the study, one was declared “BPA-free” by the manufacturer.
So, skip the can and spare your dog? It turned out, the dogs already had a small amount of BPA circulating in their blood, shown by initial baseline samples. The researchers then analyzed both the cans and the food for BPA. They also checked for any disturbances in gut bacteria and metabolic changes.
Although one of the diets was presumed to be BPA-free, feeding either brand for two weeks resulted in a three-fold increase of BPA levels in the animals. At the same time, the dogs showed gut microbiome and metabolic changes, with potential health consequences. Increased BPA may also reduce one bacterium known to metabolize BPA and related environmental chemicals, according to the study.
Bagged kibble might also contain BPA, since the dogs had some BPA in their blood before the study, possibly from their dry diets.
“This is the point that it is not clear,” Rosenfeld says. “It could be that the food already contains BPA. However, we saw minimal levels when the dogs were on kibble.” In some cases, very low amounts can lead to equally if not greater harmful effects as high doses, she says. The greatest concerns may be at the low and high doses.
“The doses we found in the dogs after being on canned food though were comparable to what has been linked to health problems in humans and rodents,” a list that includes diabetes and obesity, among others.
If the dogs continued to eat the canned food, would BPA keep building up in their bodies?
“We did not see what would happen if we took the dogs off the canned food or kept them on it longer,” Rosenfeld says. “These are definite follow-up studies.” Ideally, based on the results of this one, she says they would pursue long term studies to test BPA concentrations after long term feeding of canned food, examining the dogs for metabolic disorders—such as obesity and diabetes—and neurological ones, using MRI and behavioral testing.
In a previous rodent study, they did find that the longer mice were on a diet containing BPA, even though it was being metabolized, it would start accumulating in their system so that greater amounts would persist over time, she says.
In humans and primates, BPA is excreted through urine. “It is not clear how it is cleared in dogs.”
While BPA affects the reproductive system, Rosenfeld says they did not find any gender differences in this initial study—“but we would need to test more dogs to confirm.”
The main concern about the gut microbiome changes is that they have been linked with various diseases, including neurological, metabolic, immunological, gastrointestinal, and possibly even cancer, she says. “Thus, by affecting the gut microbiome, BPA could induce such secondary effects.”
Unfortunately, a supposedly safe substitute for BPA, BPS, didn’t fulfill its goal. Rosenfeld says that in rodents and fish, BPS has already been shown to lead to similar health concerns as BPA. Their study didn’t test BPS in the cans. “It is not clear if some dog foods are using this substitute,” she says.
“By feeding fresh food, dry food, and minimizing canned food, it will reduce exposure to BPA and BPS.”