Yes, there are some studies.
Pro raw food studies
I've found this article which mentions two studies:
A study conducted in Stockholm, Sweden by Dr. Kollath showed that young animals fed a cooked, processed diet initially appeared to be healthy, but once they reached maturity, they began to rapidly age and develop degenerative disease symptoms. The control group that was raised on a raw, uncooked diet did not age as fast and showed no degenerative disease symptoms but remained healthy.
Unfortunately they mentioned no source for this study. For the second study they linked this source:
Another study out of Belgium used data gathered from more than 500 domestic dogs over a consecutive five year time period (1998-2002). The authors, Lippert and Sapy, were able to statistically show that dogs fed a homemade diet, consisting of high quality foods used from their owners’ meals versus dogs fed an industrial, commercial pet food diet had a life expectancy of 32 months longer – that’s almost 3 years!
Cons
Nutritional imbalance
Just reading this it seems that raw feeding is really the best. But I found a summary of studies about the risk of raw food diets:
Hypervitaminosis A was reported in a cat fed a pork liver-based raw food. The cat returned to normal health when the diet was changed back to a commercial canned food. Feline pansteatitis was reported in 10 cats fed a homemade diet of cooked pig brain or raw and cooked oily fish. Nutritional osteodystrophy was reported in 2 litters of 6-week-old large breed puppies fed a bones and raw food (BARF) diet from about 3 weeks of age. Nutritional secondary hyperparathyroidism has also been reported in a litter of German shepherd puppies fed a diet of 80% rice with 20% raw meat. The diet contained excessive amounts of phosphorus. Not all puppies fed the diet experienced problems, suggesting individual or genetic susceptibility.
A nutritional analysis of 5 raw food diets (2 commercially produced and 3 home-made) found low calcium and phosphorus in 3 of the 5 diets. Two commercial diets were high in vitamin D. Two of the diets were deficient in potassium, magnesium, and zinc.
These are just some individual cases so it is not possible to say that in general the raw food diets are bad. So the same article mentions:
Supporters of raw food will argue that feeding a variety of foods will lessen the risk of nutritional imbalance.
Infectious disease risk
The same article mentions a study about the infectious disease risk:
There are several studies that document the presence of infectious agents in raw foods and the potential for contaminating or shedding these agents in the pet’s environment. A recent study analyzed 240 samples from 20 commercially prepared raw meat dog diets (beef, lamb, chicken, or turkey), 24 samples from 2 commercial dry dog foods, and 24 samples from 2 commercial canned foods. The commercial foods were collected on 4 different dates, 2 months apart. Three samples were collected from each product at each sampling point and were evaluated by culture for Escherichia coli, Salmonella enterica, Campylobacter, and by polymerase chain reaction (PCR) for Cryptosporidium, Neospora, and Toxoplasma. The PCR was performed only during the third and final sampling period. Almost 6% of the raw food diets were positive for Salmonella, while none of the conventional diets were positive. Escherichia coli were isolated from all types of diets. It
was found in almost 50% of the raw food diets but in only 8/24 (33%) dry and 2/24 (8%) canned diets. There were no significant association between the type of raw meat and the agents isolated.
In conclusion you should know which incredients your dog needs to avoid nutrition imbalance and you should keep the food fresh and cool in a clean environment, if you want to feed your dog with homemade raw food diet.
Is canned food really that bad?
I do not know what kind of food the dogs of the Belgium study were fed. In Germany dog food is handled by the German food law and the German Feedstuffs Act. That means that only ingredients humans are able to eat are allowed to used for dog food. The quality has to be the same as for humans. Indeed scrapings of slaughter are used, too, but from pigs, cows, birds, etc. which were slaughtered for human food. So the quality of the meat is very good.
There is still the question if the meat has to be raw. To answer that it is worth reminding what is happening in the stomach of a dog. The gastric acid degenerates the proteins of the meat, so that the enzyms are able to degrade the proteins. The same degenerating process is happening by cooking meat. So for old dogs it can be comfortable to eat cooked meat, because it is easier to digest.
Today there are many good dry or canned food diets for dogs. It is possible to adapt the food to the age and health condition of the dog. That is a big benefit as compared to homemade food.
So a good quality canned food is as good as a raw diet food but less risky of infectious disease.
Conclusion
At the end it is a question of believe if you prefer raw food diet or not.
It may depend on the region where you live, if you can trust the dried and canned dog food. If you buy it, (if possible) take care of the quality and how much meat is in there. The main ingredient have to be meat.
If you decide to feed raw meat homemade food, please inform yourself about the needs of a dog. They are different to humans. Take care of the quality of the food and that it is kept clean and fresh.
