In August, a report warning about fresh food causing a new type of urinary tract stone in dogs has many dog lovers concerned. Some veterinarians even sent out warnings, without doing the proper research. What are the risks and how worried should you be if you are feeding one of these fresh food brands? We discuss the science and dig into the research to find out. Before that here is a fall recipe that your pup will love.
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A rare kidney stone becomes slightly more common
Researchers at the University of Minnesota recently published a report linking a rare type of urolith (urinary tract stone) called calcium bitartrate tetrahydrate uroliths (CTT) to fresh dog foods. This has caused alarm for many consumers because kidney stones can be very painful and sometimes require surgery. Since we advocate for fresh food we wanted to understand the cause and offer our thoughts. We dug into the study that the researchers published and examined their sources of funding.
TLDR: CTT is very rare, affecting approximately 1 in 1,000,000 dogs. Official communications at the University of Minnesota (supported in part by Hill’s, the makers of Science Diet) publicly misrepresented fresh foods as the cause of rare uroliths (urinary tract stones) in dogs. The rare stones are associated with tartaric acid, a byproduct of choline bitartrate. Choline bitartrate is a synthetic vitamin that some fresh AND dry dog food manufactures use in their formulations. There were other sources of tartaric acid in the study. Because the study only looked at dogs with CTT and had no comparison group, it can’t show that choline bitartrate causes CTT—let alone make any claims about ‘fresh’ food. Thus we believe the researcher’s claims are both misleading and irresponsible.
Inaccurate claims from The University of Minnesota
The Minnesota Urolith Center processes more urinary stones than any other veterinarian center in the world. Because of this volume, their recommendations carry significant weight. Unfortunately the claims on their website are misleading.
Beginning several years ago, researchers led by Dr. Jody Lulich discovered a spike in the incident of CTT uroliths. Previously extremely rare, the new type of stone began to show up with increasing, but still low, frequency.
According to their case study, outside veterinarians asked how to prevent new stones and Dr. Lulich had a hunch. He conducted a retrospective observational study (which provide lower-certainty evidence than RCTs, see evaluating scientific evidence for more) where he concluded that the supplement choline bitartrate, a supplemental form of the nutrient choline, was often fed to dogs with CTT uroliths.
CTT uroliths are rare. According to University of Minnesota the incident is approximately 1 in 5000 submitted stones. Since uroliths themselves are rare, affecting 0.25 - 1% of dogs, this makes the incident of CTT uroliths lower than 1 in 1,000,000 dogs. Because of this limitation, the data set in the study was very small. Only 33 cases of these stones had data on dogs’ diets. Importantly, the study does not mention fresh food. Instead, researchers report that 25 out of 33 CTT cases had tartaric acid in their diet and choline bitartrate was the source of tartaric acid in 24 of those 25 dogs. Because some fresh food companies use choline bitartrate in their products, this was used as evidence on The University of Minnesota’s website (shown in the image above) to insinuate that fresh food causes the stones.
Choline bitartrate is generally in fresh food diets that are minimally processed - Dr. Jody Lulich, Co-director of the Minnesota Urolith Center
Saying that choline bitartrate is generally in fresh food is factually inaccurate. Though choline bitartrate was shown to be in formulations of several fresh food brands, other forms of choline are more common. According to researchers choline chloride is the most common form in dog foods. Furthermore, choline bitartrate is also used in kibble, for example Purina Pro Plan Elemental.
What’s wrong with their claims?
The study Dr. Lulich and his team conducted was not designed to test causation. The study only showed that there was an association between CTT and tartaric acid. Why does this matter? Since CTT is very rare and choline bitartrate appeared in many formulations, we can infer that the number of dogs who were exposed to choline bitartrate and DID NOT develop CTT is likely far greater than those dogs that DID develop CTT. Thus, their research cannot even claim that choline bitartrate causes CTT—let alone that fresh food causes it.
Veterinarians don’t do their research and rush to publish warnings about fresh food
Subsequently, a number of veterinarian practices published warnings about fresh food based on this report. Many singled out fresh food brands as being dangerous, despite the very low incident of this disorder.
Unfortunately, it appears that these vets or their teams did not read the research paper. We’ve covered in depth the challenges healthcare providers have with understanding statistics. Therefore the responsibility of the researchers to accurately report on their findings is even more important. This is particularly true of diet, as nutrition information for all the animals that vets care for is extremely diverse. It would be a herculean task to be an expert in the diets of herbivores (rabbits), obligate carnivores (cats), facultative carnivores (dogs), herbivores (horses) and more! We shouldn’t expect that of anyone.
The Minnesota Urolith Center is funded, in part, by Hill’s, the makers of Science Diet
A Hill’s press release dated November 26, 2012 indicates financial support of this group for over a decade. We requested comment from the University of Minnesota and the Minnesota Urolith Center for comment, however neither commented. This is just one of many cases raising questions about industry funding veterinary research, and a pattern of business practices by Hill’s.
This has caused some chaos, but changes nothing
We advocate for fresh whole-food nutrition. Poorly conducted studies, misinterpretation and fear-mongering by vets is disappointing, but doesn’t change the fact that all animals on earth are made to eat whole, natural foods.
There’s no way to conclude that fresh, whole foods cause rare CTT uroliths based on the data provided by researchers at The University of Minnesota,
There’s no way to even conclude that choline bitartrate causes these rare stones, because so many companies use the supplement and the incidence of CCT is still rare. We can infer that most dogs that consume it do not develop these stones.
That’s it for this week!
All the best,
Joelle and R.A.