Prescription diets

November 14, 2013   |   By David Jackson,

There's no doubt that diet can make an enormous difference to your dog's health so when he's ill, it's only right that your vet should suggest a diet change. Over the last decade or so, the 'veterinary' or 'prescription diet' has become the vet's food of choice but as we will see in this article, they might not be the best options for your dog or your wallet.

prescription veterinary diets article

Veterinary foods are promoted as the ultimate in dietary therapy for your dog - so good in fact that only your vet can give it to you. The pristine packaging, the massive price tag, the fact that they are only available through vets, even the names 'Prescription Diets' and 'Veterinary Diets' all give the overwhelming impression that these are not mere foods but medicinal treatments and must, therefore, be the best choice for your sick dog. Unfortunately, in most cases, this couldn't be further from the truth.

The most important thing to realise is that the majority of veterinary diets are just standard pet foods. Most of them don't contain anything remotely medicinal and no prescription is required to buy them. They are only available through vets because the manufacturers choose not to sell them elsewhere. They could equally choose to sell them in pet stores, feed merchants or at car boot sales if they wanted to but that would damage the air of exclusivity they have worked so hard to create. I repeat, most prescription diets are just standard pet foods.

I say most because there are still a couple of instances where veterinary diets are probably the best choice. This isn't because they are good, nutritious foods (which they certainly are not) but because they contain a certain active ingredient or property that can make all the difference to dogs with certain problems. For example, for dogs with bladder stones (also known as uroliths) specific veterinary diets are able to make the urine more acidic in order to dissolve the stones. Clearly, no normal food is going to have this effect so if your dog has bladder stones, it would certainly be best to stick with your vet's suggested food, at least until your dog gets the all-clear. Another example is dogs with severe intolerance or allergies to a wide range of ingredients. Certain veterinary diets are scientifically tailored to remove or breakdown all potentially problematic molecules so that there is literally zero chance of it causing an upset. Again though, it is best only to use these kinds of foods short term until a safe, more nutritious food can be found.

Nevertheless, these are the exceptions to the rule. Out of all the hundreds of veterinary foods out there, only a handful can claim to have any real medicinal properties. The rest, as we will see, are little more than a collection of run-of-the-mill pet foods in shiny white packaging.

Example: Hill's i/d

Hill's Prescription Diet i/d is probably the most popular veterinary diet in the UK. Vets recommend it for all sorts of gastrointestinal disorders from colitis to pancratitis, IBD to bloat. According to Hill's, it is ideal for these sorts of problems because of its high digestibility, low fat content and its high level of fibre. It also contains electrolytes to help replace losses caused by vomitting and diarrhoea and antioxidants to neutralise free radicals.

That all sounds great but actually there's really nothing unique about it. The market is awash with digestible, low fat, high fibre foods. Electrolytes (sodium, potassium, chloride, and bicarbonate) are found in abundance in any complete dog food and antioxidants have to be added to dry dog food to stop it going rancid immediately after production. So, contrary to what your vet might tell you, Hill's i/d is just one of many diets that might fit the bill for a dog with digestive upsets but, as we will see from the ingredients, it certainly isn't the best.

Hills i/d dry ingredients: Ground MaizeClick to see what we think about Maize / Corn in dog food, Ground RiceClick to see what we think about Rice - White in dog food, Dried Whole EggClick to see what we think about Egg in dog food, ChickenClick to see what we think about Chicken in dog food and Turkey MealClick to see what we think about Turkey in dog food, Maize Gluten MealClick to see what we think about Maize Gluten in dog food, DigestClick to see what we think about Digest in dog food, Dried Beet PulpClick to see what we think about Sugar Beet in dog food, Animal FatClick to see what we think about Unspecified Animal fats in dog food, Vegetable OilClick to see what we think about Vegetable Oil in dog food, Calcium CarbonateClick to see what we think about Calcium Carbonate in dog food, FlaxseedClick to see what we think about Linseed in dog food, Potassium Citrate, SaltClick to see what we think about Salt in dog food, Potassium ChlorideClick to see what we think about Potassium Chloride in dog food, Dicalcium PhosphateClick to see what we think about Calcium Phosphate in dog food, TaurineClick to see what we think about Taurine in dog food, L-Tryptophan, Vitamins and Trace ElementsClick to see what we think about Vitamins and Minerals in dog food. Contains EU Approved AntioxidantClick to see what we think about Artificial Preservatives in dog food.

It doesn't take a nutritionist to tell you that this is not a great food, but I'm going to anyway. The first, and therefore most abundant ingredient in Hill's i/d is maize - a grain that has become increasingly associated with dietary intolerance and actually causing digestive upsets. Add in the second ingredient rice and the added maize gluten further down and it's clear that i/d is a very grain heavy food. As dogs are primarily designed for digesting meat, this is not the best characteristic for a food to aid digestion. Meat, in fact, is only the 4th ingredient on the list and since the percentage isn't specified, the actual amount in the food could be very low indeed. The remaining ingredients really aren't anything to write home about either - digest, unidentified animal fats, added salt and even artificial antioxidants - all hallmarks of a low grade food. All of this adds up to the fact that Hill's i/d is a pretty bad dog food - by our standards, it scores just 1.8 out of 5 and yet your vet will charge you upwards of £60 for a 12kg bag!

The story is the same for just about all of the veterinary diet ranges out there:

  • Hill's r/d dry for overweight dogs: 2.4 out of 5
  • Hill's j/d dry for joint support: 1.7 out of 5
  • Hill's t/d dry for oral hygiene: 1.8 out of 5
  • Royal Canin Anallergenic dry for reducing intolerances: 1.4 out of 5
  • Royal Canin Dental dry: 2.0 out of 5
  • Royal Canin Gastro Intestinal dry: 2.1 out of 5
  • Purina HA Hypoallergenic: 1.2 out of 5
  • Purina EN Gastroenteric dry: 2.0 out of 5
  • Purina OM Overweight Management 1.2 out of 5

So why do vets sell veterinary diets?

There are several reasons why prescription diets have become so prominent within the veterinary industry: Firstly, as disillusioning as it might be, many vets just don't know any better. Nutrition makes up a very small part of veterinary training and of the few modules that are available, many are 'sponsored' by the manufacturers of veterinary diets themselves. Veterinary undergraduates learn that a dog suffering from condition x must be fed veterinary diet y. Other brands and feeding philosophies just don't get a look in so by the time newly graduated vets join their first vet practice, veterinary diets really are the extent of their dog food knowledge.

Then, of course, there's the money. Veterinary diets are incredibly expensive, the markup for the vet practice is huge and since you can't get them elsewhere, it makes good business sense for a vet to get you on to them. The manufacturers and distributors of the veterinary diets also offer massive cash incentives to practices that meet their sales targets - so large in fact that winning or losing the bonus can make a considerable difference to a practice's prosperity. With so much at stake, it's no surprise to find vets pushing veterinary diets so vigorously.

The Golden Rule

These days, specialist veterinary diets are available for everything from obesity to 'brain ageing' (whatever that is). The golden rule: if your dog is overweight or has problems with his teeth, digestion, joints or skin, he does not need a veterinary diet, he just needs a good diet - in fact, there are dozens of 'normal' foods that will probably be far more beneficial at half the price. You can use our Dog Food Directory to find the best food for your dog.

Prescription diet alternatives

Even a lot of more serious conditions like heart problems, diabetes, kidney disease and liver disease can arguably be managed just as effectively on some normal foods as on veterinary diets. The table below shows some of the biggest selling prescription diets and the characteristics that apparently make them uniquely suitable for dogs with particular health problems. As you can see, there is nothing extraordinary about any of these prescription foods - no medicines or active ingredients at all and every nutritional characteristics that they do have (like being highly digestible or low in fat for example) can be found in other over-the-counter foods at a fraction of the price.

Category of illness Condition Top vet diets Nutritional characteristics
Gastro Intestinal Gastritis / enteritis / IBD / colitis / EPI / Pancreatitis Hill's i/d
Royal Canin Gastro Intestinal
Purna EN Gastroenteric
High digestibility
Low fat
High fibre
Diabetes Diabetes Melitus Hill's r/d
Royal Canin Diabetic Dog DS37
Purina DCO Dual Fibre Control
High fibre
No added sugars
Kidney Chronic kidney disease Hill's k/d
Royal Canin Renal
Purina NF Kidney Function
Low phosphorus
Low sodium
High fibre
Urinary stones / crystals Urate / cystine / oxalate - prevention only Hill's u/d
Royal Canin Renal
Low protein (high quality)
Low calcium
Low nucleic acids
Low phosphorus
Low Sodium
Struvite / calcium phosphate - prevention only Hill's c/d
Royal Canin S/O
Low protein (high quality)
Low magnesium
Low phosphorus
Liver Liver disease Hill's l/d
Royal Canin Hepatic
Low protein (high quality)
Low copper
High fibre
Low sodium
Heart Heart disease Hill's h/d
Royal Canin Cardiac
Low sodium
High taurine / l-carnitine

The bottom line

Vets are there to help so we certainly recommend following their advice in all aspects of your dog's health but when it comes to diet, it's always best to ask a few questions. If your vet suggests moving to a veterinary diet (or any other diet for that matter), make sure you ask them why. Don't take "because it's specially designed for dogs with this condition" as an answer - we need specifics. If there's a genuine reason why that food would be the best choice for your dog, then go for it. If not, look for alternatives and if in doubt, get in touch.


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