animal health consulting

"Purina Pro Plan Veterinary Diets CC CardioCare represents a breakthrough in the role nutrition offers for dogs with early stage mitral valve disease. The novel scientific approach has led to the development of a transformational diet that slows progression of the condition in dogs." — Dr. Jason Gagne, DVM, DACVIM (Nutrition)

Now let's talk about the dogs in this study and then finish with a closer look at the diets.

The study

In 2019, the folks at Nestlé Purina Research in St Louis, Missouri published the study on which their claim ("slows progression") is based:

Li Q, Heaney A, Langenfeld-McCoy N, Vester Boler B, Laflamme DP. Dietary intervention reduces left atrial enlargement in dogs with early preclinical myxomatous mitral valve disease: a blinded randomized controlled study in 36 dogs. BMC Veterinary Research 2019; 15: 425. full text here

Note the publication date: only 3 years ago.* We don't yet have any independent data on how this diet performs in the real world.

* Submitted 22 July 2019, accepted for publication 07 November 2019,  published online 27 November 2019.

The study was funded by the Nestlé Purina PetCare Company, and all authors were either employees or paid consultants of the company. In other words, this was not independent research.

We've examined most of the published data. I simply want to note here that, when a company is both funding and conducting a study, results that are not favourable to their financial bottom line tend to be left out or diminished in some way.

The dogs

As the title of the paper indicates, a total of 36 dogs were enrolled in the study. However, that is rather misleading, as it appears to suggest that 36 dogs with early mitral valve disease were fed this CardioCare prototype. In fact, only 10 dogs with mitral valve disease were fed this diet.

Of the 36 dogs, 35 dogs completed the 6-month study. One dog with mitral valve disease fed the CON diet was removed after 3 months because s/he had lymphoma that was not present/apparent at the start.

While it may be tempting to blame this junkfood diet, we should make nothing of this one dog's removal. In pretty much every clinical study that follows a group of individuals for a period of weeks or months, there are drop-outs, and the reason(s) may have nothing to do with the study. It would not be unusual for lymphoma to be lurking, undetected, for 3 months or more before diagnosis. So, we'll let this poor dog lie, except to note that her/his removal from the study further reduced the number of dogs in that control group...

What I haven't mentioned at all yet is that there was a separate Control group of 17 healthy dogs. They were divided into two groups, one fed the CON diet and the other fed the CPB diet. Their outcomes were not particularly interesting, so I won't spend any time on them when there's so much more to discuss.

Here is the final breakdown of the 36 dogs into their respective groups:

* HEALTHY, fed CON diet (8 dogs)

* HEALTHY, fed CPB diet (9 dogs)

* MITRAL VALVE DISEASE, fed CON diet (initially 9 dogs)

* MITRAL VALVE DISEASE, fed CPB diet (10 dogs)

There are four things about the dogs that I want to highlight, in relation to how well the results of this study can be applied ('generalised') to all dogs everywhere:

1. Most of the dogs (32 of the 36 dogs, or 89%) were Beagles; the other four dogs were Miniature Schnauzers.

There was one Min. Schnauzer assigned to each of the four groups, so in all groups the predominant breed was the Beagle.

How well do these two breeds represent those at high risk for mitral valve disease, such as the Cavalier King Charles Spaniel? Probably not as well as this study would have us believe.

2. The study was conducted in a research facility, using research animals.

The dogs were selected from those "living at a Nestlé Purina PetCare Center." (The mind boggles...) We aren't told much more about these dogs, but generally such dogs are purpose-bred research animals, rather than purchases, rescues, or donations.

The dogs were "housed individually in adjoining indoor-outdoor runs with natural and additional lighting on a 12 h cycle. Open access was provided between adjoining runs except during feeding. In addition, all dogs were provided regular exercise such as walks and time in play yards, and daily socialization with other dogs and caretakers."

"Dogs were individually fed once daily to maintain stable body weight throughout the study. No treats or other supplements were allowed during the course of study."

That's good, in terms of uniformity in diet and lifestyle factors that may affect heart health. But how well does such a study reflect the diet, lifestyle, and social interactions of pet and performance dogs belonging to people who love them? All of those things matter in heart health.

3. The study lasted for only 6 months.

Most of the dogs were seniors (average age, 10-11 years), which is good, but we have no idea what happens after 6 months on this diet, nor what happens when the diet is started before there is any change in mitral valve structure and function in high-risk breeds.

Oh, and the Healthy group included dogs as young as 19 months, whereas the youngest dogs in the mitral valve disease group were 8 years old. I think that may have been incidental or considered inconsequential, but it is an avoidable error (or a typo, which is also an avoidable error).

4. There were only 10 dogs with mitral valve disease fed the CPB diet, and another 8 fed the CON diet.

Of the 19 dogs with early mitral valve disease who were enrolled in the study, only 10 were fed the CPB diet. Initially, 9 other dogs with early mitral valve disease served as the diseased-control group (fed the CON diet), but only 8 of them completed the 6-month trial.

These are very small numbers on which to be basing the claim that this diet "slows progression of the condition in dogs."

One of the hallmarks of good study design is that the results can reliably be generalised to the population the study participants are meant to represent (e.g., all dogs, or at least all dogs with/at risk for mitral valve disease), and so the results are later validated by real-world use.

But when almost all of the dogs were Beagles, all were research animals housed in a research facility, the dogs were studied for only 6 months, and there were only 8–10 dogs per group, it is a real stretch to claim that these results are generalisable to the entire dog population or to all dogs with early preclinical mitral valve disease ("slows progression of the condition in dogs").

The diets

Now to the most important stuff: what these dogs were eating!

(Thank you for reading this far. It was important that you did, but I realise it was quite the slog :-)

CON diet

Here are the constituents of the CON diet:

* basal diet mix, 90.7%

This mix was "composed of grains (corn, rice, wheat), proteins (poultry, corn gluten, corn germ meal), dietary fibers (beet pulp, cellulose), vitamins and minerals, and flavouring additives."

In other words, junkfood. And by the way, "poultry" is a bit of an overstatement... the fourth ingredient in CardioCare is "chicken meal," which is any and all parts of the chicken not fit for human consumption; it can legally include '4D' birds (dead, dying, diseased, or down).

* egg protein, 2%

* beef fat, 9.3%

Those two additions to the basal diet mix were made to ensure that both test diets (CON and CPB) were similar in protein, fat, and total calorie content. That's good, as a difference in these nutrient classes between diet groups could have influenced the results.

(BTW, if you added up those numbers — which I triple-checked — and arrived at a total of 102%, well done! How did that get past the reviewers?!  I despair...)

CPB diet

Here are the constituents of the CPB diet:

* basal diet mix, 86% [contents as above]

Note that the first three ingredients listed for the commercially available CardioCare are "oat meal, corn gluten meal, rice"...

Both the CON and CPB diets were ~ 45% carbohydrates.

* MCT oil, 5%

MCT = medium-chain triglyceride. (I'll let you look that up on Wiki if you're interested.) MCT oil is typically made from coconut oil, purified to isolate and concentrate the medium-chain triglycerides. It's now widely available in grocery stores. It's a clear, tasteless, odourless oil that's only a little more expensive than other high-quality vegetable oils.

* fish oil, 2.9%

* fish meal, 3.4% [akin to "chicken meal"... parts not fit for humans]

* L-lysine, 1.3% [lysine is an essential amino acid]

* DL-methionine, 1% [methionine is an essential amino acid]

* taurine, 0.13% [taurine is an amino acid that, while not essential, may be beneficial]

* magnesium sulphate, 0.2%

* DL-alpha tocopherol, 0.15% [synthetic vitamin E]

Based on research in humans and lab animals, all of these additions have a potentially beneficial role in heart health. One thing I really like about this paper is that the authors discuss each nutrient/foodstuff and the specific role it may play in heart health. In that regard, it's a very handy reference, and I encourage you to download it and read it in full.

However, those nutrients are doing some very heavy lifting by being added to the standard, grain-heavy, byproduct-laden, highly-processed Purina fare. The best we may be able to say about the CardioCare prototype (CPB diet) is that it performed a little better than Dog Chow or whatever Purina product the dogs on the CON diet were fed. (And what an amusing abbreviation CON is here... :-)

Incorporating what we've learned

Here is my main take-away from this study: adding some of these "heart-healthy" nutrients to a fresh, species-appropriate diet might be able to delay the onset and slow the progression of mitral valve disease in at-risk breeds.

MCT oil is easy to come by, as I mentioned above. You'll most likely to be able to find it in your grocery store. Natural grocery stores will definitely carry it if you strike out closer to home.

As for what 5% of the diet looks like, let's keep it simple. If you take 100 grams (a little under half a cup) of moist food, canned or fresh, 5% = 5 grams = 5 mls (cc), or roughly 1 teaspoon. Scale up or down from there, as appropriate.

Don't overdo it at first if the dog has a history of pancreatitis. Start low and work up to the amount used in this CPB diet.

Fish oil is also easy to come by, although here (as in most areas of nutrition) quality matters. Spend the money on the good stuff, tested and guaranteed to have negligible amounts of mercury and other heavy metals.

As for what 2.9% of the diet looks like, I would question whether amount is all that important in a wholesome, species-appropriate canine diet. If you're emphasising grass-fed and -finished, pasture-raised, or wild-caught meats, dairy products, and eggs, and including leafy greens as well, then you're probably doing pretty well on the omega-3 fatty acids already — especially if you're including oily fish (sardines, kippers, salmon) in the dog's diet at least a couple of times a week.

That brings me to the fish meal component of the CPB diet. Fish meal is a very unpleasant and not very healthy byproduct of the human food industry. It's all the parts not fit for humans to eat.

Fish itself is a high-quality protein source, and is well used by dogs. However, I would not feed fish meal; instead, I would feed fish as a component of the meat portion of the dog's diet. Feeding oily fish for their omega-3 fatty acid content is doing double duty by also providing a higher-quality protein than fish meal could ever hope to provide.

As for lysine and methionine, they too should be well supplied by a wholesome, species-appropriate diet. That said, there is no harm in adding them to the diet in a dog who has already been diagnosed with mitral valve disease, or who is a mature dog of a high-risk breed. How much? Who knows! This is all still experimental, and don't let Purina convince you otherwise.

From the NRC guidelines (Nutrient Requirements of Dogs and Cats, 2006), the basic or maintenance requirement of each for an adult dog weighing 23 kg (50 lb) is 1.14 grams/day. (That's 1,144 milligrams.)

Same goes for taurine. A species-appropriate diet, which for dogs is a meat-based diet, should supply ample taurine. But if you want to feed more taurine, then feed heart at least a couple of times a week. Chicken, lamb, and beef heart are widely available, although you may need to special-order heart through your butcher if it's only sometimes available in the refrigerator or freezer case at your local grocery store.

There is no specified requirement for taurine in dogs as there is for lysine, methionine, and various other essential amino acids. That should tell you something about the importance of adding taurine to an already wholesome, species-appropriate canine diet.

Magnesium, ditto: a healthy, species-appropriate canine diet should supply ample magnesium. If you simply must supplement it or you'll burst with anxiety, then be conservative. Magnesium needs to be supplemented with due consideration for the calcium, phosphorus, and vitamin D content of the diet.

Really, it's best to let nature do it. As long as you're including some dark-green plant foods in the dog's diet, you'll likely be supplying ample magnesium — because chlorophyll (the green pigment in plants) is rich in magnesium. (Magnesium is to chlorophyll what iron is to haemoglobin, the molecule that makes blood red.) Bone, fresh or as bone meal powder, also contains magnesium.

From the NRC guidelines (Nutrient Requirements of Dogs and Cats, 2006), the basic or maintenance requirement of magnesium for an adult dog weighing 23 kg (50 lb) is 205 mg/day. That's not a lot, and all of it should be coming from the dog's diet, not from a jar.

BTW, magnesium sulphate (MgSO4) is only ~ 20% magnesium; the rest is the sulphate ion. So, the inclusion rate of 0.2% MgSO4 supplies ~ 40 mg magnesium per 100 grams of this food.

Lastly, vitamin E. Again, if you're feeding a wholesome, species-appropriate canine diet, then your dog is probably getting ample vitamin E. As vitamin E is a fat-soluble vitamin, the fatty foods in the dog's diet, both animal and vegetable, primarily supply vitamin E. If you want to supplement it, which isn't a bad idea in mature and senior dogs dealing with chronic disease of any sort, then be conservative. More is not necessarily better.

From the NRC guidelines (Nutrient Requirements of Dogs and Cats, 2006), the basic or maintenance requirement of vitamin E (alpha-tocopherol) for an adult dog weighing 23 kg (50 lb) is 10.4 mg/day. Make sure it's a natural-source vitamin E, not the synthetic stuff.

Here's a link to a handy calculator for figuring out how much of each nutrient your dog needs, according to body weight.

*****

That's it for now. If I think of anything else, I'll add it later. Here's wishing you and the dogs you love health and wellness for many years to come!

© Christine M. King, 2022. All rights reserved.

First published 21 September, 2022. Last updated 24 September, 2022.

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