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Thursday, April 1, 2021

Pondering Prescription Diets: Science or Scam?

As our pets age (sometimes even in youth) it is a sad reality that they may develop chronic health conditions requiring long-term management. Luckily, as modern medicine marches forward, the treatment options available continually expand. Astute pet owners may take notice of the ever-growing array of dietary solutions marketed for disease management in companion animals. These diets, available both online with a prescription or directly through veterinarians, provide tailored nutritional support for conditions of the skin, gut, liver, kidneys, urinary bladder, and even brain. Par for the course of nutrition information available online, however, misconceptions and misplaced criticism abound. A common allegation states that these diets are scams, because they don’t contain specific medications, they use ingredients similar to those of traditional diets, and they’re often expensive. This has led some pet owners to question why a prescription is even necessary! Like with most pet food misconceptions, a bit of background information readily remedies these concerns.

Why don't these diets contain medicine? 

Therapeutic diets are not intended as a way to deliver medications to pets. Rather, they are meant to modify nutritional factors as they relate to certain diseases. In many cases, these diets are given along with, not instead of, medications. The good news is, they don’t need to contain ‘medicine’ to help pets! The nuance can get complicated, but simplified examples can illustrate this. For pets with kidney disease, diets lower in phosphorus and protein can help slow the progression of disease. Phosphorus, in particular, can exacerbate damage to the kidneys in animals that have kidney injury (though it is safe and essential as a nutrient at recommended levels for healthy pets!). Animals with liver disease can develop problems with copper storage, necessitating a diet low in copper. They may be unable to clear certain waste products from their blood as effectively (a major job of the liver!), and benefit from a lower protein diet, since some of those waste products come from protein digestion. To reduce the formation of urinary crystals and stones, diets may be low in calcium, phosphorus, and magnesium. With less of these compounds in the diet, less end up in the bladder, which reduces the risk of them combining to form stones. Urinary diets are also often high sodium, to encourage water intake and dilute the urine. It might surprise some to know that studies have shown that a high sodium diet is safe for an otherwise healthy animal, as normal mechanisms in the body encourage additional water consumption and offset the sodium intake. These diets may not be appropriate for an animal with kidney or heart disease, though. A specific feline diet for treating hyperthyroidism is very low in iodine. Iodine is essential for normal function of the thyroid, but for a cat with an overactive thyroid, limiting iodine intake can help reduce the overproduction of thyroid hormones. All of these examples are to say that by modifying the levels of normal nutrients, it's possible to help manage disease, and no medication needs to be in the diet for those nutrient levels to be controlled. 

Why are these diets prescription only? 

Once consumers know that these diets don’t contain ‘medication,’ they wonder why a veterinary prescription is needed to purchase them. There are both safety and regulatory reasons for this. When the body has disease, the way nutrients are utilized by organs changes too. Pet foods on the shelf for anyone to purchase are formulated to meet certain nutrient requirements for the average, healthy animal. These minimums are outlined by organizations like AAFCO (Association of American Feed Control Officials) and the NRC (National Research Council). When the nutrient compositions of diets are changed to better accommodate certain disease processes, the nutrients may fall below or above the levels recommended for an average, healthy animal. While an animal with a specific disease may benefit from the diet, a healthy animal may be harmed by it. Additionally, many of these diets (and diseases) require ongoing monitoring by a veterinarian to make adjustments over time, or decide when the diet may need changed again. Not all of them are necessarily safe for long-term use, but may have benefits that outweigh the risks to certain groups of severely ill pets. That risk-benefit needs to be continually re-evaluated. For those reasons, it is best if the diets are only used under the recommendation and supervision of a licensed veterinarian. 

There is also regulatory reasoning! Under FDA definitions and statutes, a diet marketed to treat or prevent a disease is technically classified as a ‘drug,’ as well as a ‘food.’. This has the potential to complicate the use of these diets, which do not undergo the same approval processes as pharmaceuticals generally considered ‘drugs.’ Such approval processes are often lengthy, and requiring every prescription diet to undergo that process could effectively limit their availability and keep them from pets who benefit from them. In recognizing this, the FDA has said that enforcement action will likely not be taken so long as several factors are present, including that the diet is only available under the direction of a veterinarian. 

Why do they cost so much?

While the types of ingredients used may be similar, the manufacturing process for these diets is sometimes more stringent. For example, hypoallergenic prescription diets have to be made on a pristine manufacturing belt to avoid cross contamination that could cause a reaction in a dog eating the diet to avoid food allergens. These foods may also sometimes contain greater amounts of potentially therapeutic ingredients, which may be more expensive than the amounts provided in traditional diets. Even when general manufacturing practices don’t differ, the overhead cost of these diets is often more for a simple reason: extensive research! These diets are the product of decades of nutrition research to identify what interventions might benefit sick animals and assess how well the diet actually achieves those goals. Funding the research translates to higher retail price. Despite this, and perhaps surprisingly, while the diets are often more expensive than their traditional counterparts, Dr. Doherty, economic analyst for the Ontario Veterinary Medical Association, found that they cost about the same as some ‘premium’ pet store diets. Even with the higher end price tag, it’s also worth considering the indirect savings associated with dietary disease management. A urinary diet could prevent surgery, for example, and that is a big monetary savings! An animal benefiting from a renal diet may stave off the need for intensive hospitalized care. While these diets can’t always prevent the eventual decline of patients with severe disease, and they don’t eliminate risks, they can often reduce the severity or speed of a disease, and that may save money as well as provide a longer, more comfortable life for a pet.

With the above considerations in mind, it’s easy to see that prescription diets are indeed science, not scam! While they do not contain medication, and they often use the same or similar ingredients, they are formulated with certain nutrient changes in mind to tailor to specific disease states and help sick animals, based on extensive nutrition research. Always be sure to talk with your veterinarian if you have any specific questions about your pet and their diet needs. 

Has your pet benefitted from a prescription diet? Leave a comment below with your experience!!

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(Image via Pexels, Emma Charles DVM, author at


  1. Interesting that these diets are prescription only where you are. In the UK they are freely available to buy. I can see the benefits of having them prescription only but would be curious to know if this means you're limited to whichever brand your vet prefers.

    My understanding is that over here, a diet is 'prescription' and held to that higher standard if they are making specific health/treatment claims. For me, this gave me more confidence shopping around for what was most suitable for my dogs and budget. I've had to use renal and urinary diets for my dogs and so far, so good.

    1. Thanks for commenting! In my experience, you typically aren't limited to your veterinarians preference. Most of the vets I've worked with will make an initial recommendation based on which one they have the most experience with, but they'll still write a prescription for a similar diet from a different brand if a client requests they'd like to try it.

      Alternatively, some vets will make their recommendation less about the preferred brand and more about which brand's diet is the best fit for a specific pet. Purina and Hill's and Royal Canin all have diets for kidney disease... but they differ slightly in terms of calorie content, macronutrients, and the micronutrients. Depending on what stage of kidney dysfunction a patient has, one diet may be better than another, and a veterinarian can help guide the client through that decision.

      The prescription diets available here do have a "higher standard" so to speak in that their label claims are supported by research and evidence that they actually do help to treat or prevent a specific condition. The position here is essentially that it isn't safe for a consumer to decide what is most suitable for their dog without veterinary input, because ultimately it is a medical decision. That doesn't mean there isn't room for a conversation with the veterinarian about what options are available and how they fit into a budget, though.

      I'm glad you've seen success with the diets for your dogs so far! My dog had to be on a prescription weight loss food, she wasn't staying lean on the calorie restricted diets available over the counter, and she did wonderful.


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