– Considering that dogs often eat the same food daily for long periods of time, sometimes even their whole lives, we need to acknowledge the risk for long-term accumulation of contaminants such as toxic metals. Arsenic is widespread in the environment and accumulates especially in the rice plant. Since rice is a common ingredient in dry dog foods, we wanted to know if this could be a risk for chronic arsenic exposure in dogs, says PhD student Sarah Rosendahl from the Faculty of Veterinary Medicine.
The pilot study compared hair arsenic levels from seven dogs that were eating rice-based (having rice as first or second ingredient) dry dog foods and nine dogs whose diet did not contain any rice. All dogs were of the breed Staffordshire bull terrier and had been eating their diets for a minimum of one year prior to the study.
According to the study, the dogs that were eating rice-based dry dog foods had higher hair arsenic levels compared to the dogs that were not eating any rice. The mean arsenic level in the dogs that were eating rice-based dry dog foods was also higher than the arsenic levels seen in dogs in previous studies.
– It was interesting to see that the dogs with the lowest arsenic levels were all eating raw food diets. For example, the dog with the most arsenic had a 3.5 times higher arsenic level than the dogs with the least arsenic, says Rosendahl.
Even though the difference in mean arsenic levels between the two groups was statistically significant, the difference was quite small. This means that from a toxicity viewpoint, the differences might not be significant. Research on arsenic toxicity in dogs is limited and has mostly focused on kidney damage associated with higher levels of arsenic than was seen in this study. However, a variety of chronic diseases, such as cancer, diabetes and neurological disorders, have been associated with low-level arsenic exposure in humans. Especially people eating gluten-free diets, in which rice is a common staple, have been found to have elevated arsenic levels.
– Based on what we know today, our results do not indicate that eating rice-based dry dog foods is toxic or dangerous for dogs. However, due to the negative health effects associated with chronic arsenic exposure in humans, we cannot ignore the possibility of similar effects in dogs. Until there is more research, it would be advisable to avoid feeding dogs rice-based diets for very long periods of time and instead feed a more varied diet, says Rosendahl.
The study used hair mineral analysis by inductively coupled plasma mass spectrometry (ICP-MS) to measure arsenic levels from the dogs’ fur. This method has been widely used in human research, and lately it has been getting increasing attention in dog research as well. The benefit of using hair is that it gives a better reading of long-term levels, while blood levels can fluctuate rapidly. Based on the results of this study, hair mineral analysis can be considered an informative, cheap and non-invasive method to measure arsenic levels in dogs.
– We were very excited to confirm the usefulness of hair mineral analysis in this study. Hair mineral analysis is a very interesting method and we plan to use it in future studies as well, Rosendahl says.
Rosendahl, S., Anturaniemi, J., Hielm-Björkman, A.
(2019) Hair arsenic level in rice-based diet-fed Staffordshire bull terriers
Veterinary Record Published Online First: 30 October 2019. doi: 10.1136/vr.105493