With so many benefits reported on the internet anecdotally, it's unsurprising that the raw food movement has become so popular. We've listed the most commonly claimed 'benefits' below and delved into each one a little deeper.
1. Palatability.
Many pet owners find their cats or dogs prefer the taste of a raw meat diet, and that it's easier to tempt fussy eaters. This is easy to imagine, and is of course more of a general statement. While there has been research which suggests that dogs prefer to eat high meat diets over high carbohydrate diets1, there has not been the same level of research into whether raw meat is more palatable than cooked meat or other types of pet food. We are happy to conclude that the palatability of a raw diet depends on the diet itself and your pet's personal preference.
2. It Mirrors The Ancestral Diet.
Many believe that a raw diet is better because it is closer to your pet's natural, ancestral diet. The theory goes that dogs should be fed a diet that mirrors their wild ancestors, the Grey Wolf, due to DNA similarities. This 'ancestral diet' theory argues that the dog's anatomy (ie teeth designed for cutting and slicing, shorter intestinal tracts) is built for a carnivorous diet.
This is a nice thought, but if this idea is to be considered as justification for a raw meat diet, there are a few important points to consider:
- Your dog is not a wolf. Dogs were domesticated by humans approximately 33,000 years ago, and consequently have evolved considerably. While there is evidence to suggest that dogs do not require carbohydrates1, they have certainly evolved the ability to digest them. A life alongisde humans brought with it a much more varied diet, which over time saw dogs evolve a number of features that allowed them to digest plant-based foods2. These features include an increased gene expression for pancreatic amylase, the ability to convert maltose to glucose, and increased uptake of intestinal glucose. Therefore, dogs are generally considered biologically omnivorous. Early wolves had none of these genetic abilities. In fact, dogs share only 98% of their DNA with wolves - about as much as humans share with bonobos.
- Early wolves had a very short lifespan. Depending on their size and breed, the average domestic dog can live up to 20 years (sometimes longer!). Whereas the lifespan of a wild wolf is only around 5 years. This not only demonstrates the difference between the two species, but it also helps us understand how 'living wild' doesn't always mean 'living better'.
- Hunted meat is not the same as meat from your local shop. There is a perception that feeding your dog raw meat from the butcher is as good as your dog consuming freshly killed prey. But think about how different it is in terms of hygeine. Meat from freshly killed prey is just that - fresh. Wild dogs devour meat from their prey within 1-2 hours of the kill. Whereas, store bought meat has been handled in an abattoir, transported, and refrigerated over at least 1-2 days by the time it is finally fed (and that is fresh, human grade product). So, there is a lot of time for nasty bacteria to grow. This is why us humans don't eat raw meat from the butcher. Contrary to popular belief, dogs are just as likely to get food poisoning as we are. Dogs on raw meat diets often experience mild bouts of loose stool, and have been found to shed much larger quantities of harmful bacteria in their faeces - including Salmonella, Listeria and Yersinia spp3,4,5, which can be spread to humans. Read more about this below.
3. Increased Digestibility
Raw diets are believed to be easier to digest because essential nutrients such as enzymes, vitamins, and amino acids haven't been destroyed by cooking.
- On the enzymes: Yes, it's true that certain enzymes found within food are destroyed during the process of cooking6. But in general, these enzymes aren't necessary for digestion. Cats and dogs already have all the enzymes they need within their gastrointestinal tract and pancreas, and don't require exogenous enzymes for digestion. Plus, most enzymes from raw food are destroyed in the stomach anyway.
- On the digestibility: Regardless of enzyme activity, are raw diets still more digestible? There are actually a number of studies7,8 in different species of cats that have indeed found raw food to be more digestible - however one of these studies found that this is mostly just in terms of protein (ie, the digestibility wasn't improved for fat, carbohydrates, or energy).
So does this mean that protein is more bioavailable if it has been cooked? Interestingly, the effect cooking has on protein depends on what type of ingredient the protein is drawn from - in particular, whether it is from plant material or meat. (Remember - plants provide protein too!). For protein derived from meat, heat processing can have negative effects and reduce its bioavailability. But for protein derived from plants, cooking can actually improve the bioavailability. This is because the heating process denatures some of the antinutritional factors that are naturally found in plants. For instance, legumes contain trypsin inhibitors that reduce bioavailability of protein. Heat processing denatures these inhibitors and therefore increases protein bioavailability, making legumes easier to digest after cooking.
What does improved digestibility mean? Ultimately, higher digestibility = smaller, firmer poos. (See our next point for more about this!)
4. Smaller, firmer stools with less odour
Another proposed benefit of raw diets is that they create smaller, firmer stools with less odour. In general, this is believed to be true - but it may not be due to whether the food is raw or cooked, but more about the meat vs carbohydrate content. (Typically a higher meat content diet produces smaller, firmer stools)1. Plus, whether there is a 'difference' or an 'improvement' really depends on what you compare it to. For example, if you swap your dog onto a raw diet after previously feeding them cheap, poor quality supermarket food, then you will likely notice a big reduction in stool size. However, if you already feed a premium diet that is already high in meat content, you might not notice much of a difference in stool size if you swap over to a raw diet.
What causes smaller stools?
As mentioned, a high meat content can contribute to smaller stools. But in general, it really comes down to digestibility. If the diet has a high level of digestibility, this results in less digest in the colon, and therefore less faecal output.
But are smaller stools actually a good thing? Smaller stools are without a doubt better for the pet owner, as it means you'll have smaller, less smelly landmines to pick up in the yard! But with regards to your pet, small stool size doesn't automatically mean a happier tummy.
It's easy to assume that smaller stool size must mean that your dog has a healthier gut. For the most part, this is true - however it is a little more complicated, and depends on why the faeces is so bulky. In particular, it comes down to the ingredient in question, and whether the ingredient is of plant or animal origin.
Bulky faeces could be due to undigested plant matter, or undigested meat (or a combination of both). Undigested plant matter in the form of fibre has been shown to be beneficial for the gut, as it feeds the 'good bacteria' present in the colon. (So a bit of bulky poop could be good for your dog if it's due to high quantities of beneficial plant fibre!)
However, undigested meat protein can result in unfavourable compounds such as ammonia, phenols, insoles, and amines - which can play a role in diseases such as colorectal cancer9.
Ultimately, this means that while a raw meat diet may in fact create smaller stools, this doesn't automatically mean your pet has a healthy gut, as a little bit of 'bulk' can be a good thing if it's due to plant fibre.
5. Improved Immune Function.
Another claimed benefit of raw diets is that it can improve your pet's immune system. Interestingly, this claim may also hold some merit. A study conducted on domestic cats fed a raw diet for 10 weeks observed a significant increase in lymphocyte (immune cells) and immunoglobulin production, compared to a control group who were fed a commercial canned diet10. However, it's possible that these increased levels of immune cells were due to exposure to Salmonella in the raw meat, as the cats fed the raw diet were also found to be shedding higher levels of this bacteria in their faeces. Other possible reasons for this immune cell increase include exposure to pathogens, changes in the gut bacteria, or nutritional deficiencies.
So ultimately, it's possible that a raw diet could stimulate the immune system and improve immune function. But it's also possible that this is simply due to higher levels of bacterial contamination, which brings with it its own risks. See below for more about this.
6. Decreased risk of cancer.
Many pro-raw advocates claim that a raw meat diet can reduce your dog's risk of cancer. There is actually potential for this claim to hold merit, but further testing is required.
How could a raw diet decrease your dog's cancer risk?
The mechanism comes down to the effect cooking has on the food. When muscle meat is cooked at high temperatures, it produces compounds called heterocyclic amines.11 In very high concentrations, these compounds have been associated with cancer. While the concentrations of heterocyclic amines found in pet food are quite low12, it's possible that they still may have mutagenic activity. It's unknown whether there is a cumulative effect of excess exposure to these compounds, but further testing is required to know for sure.
