the scientific study of pet nutrition by veterinary nutrition specialists and experts.

Much Ado About Therapeutic Diets

Much Ado About Therapeutic Diets
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In December, a class-action lawsuit was filed in California alleging that several major pet food manufacturers and retailers are engaging in price fixing by limiting specific diets to sales only by veterinarians or with veterinary permission. This lawsuit highlights the numerous misunderstandings that many pet owners have about therapeutic diets (AKA “veterinary diets”) and how they are regulated by the government.

The Food and Drug Administration (FDA) currently broadly prohibits foods or supplements being sold that are intended to “diagnose, cure, mitigate, treat, or prevent disease”. Products that make any of these claims are considered to be drugs, and must complete a multi-year, complex, and costly drug-approval process before being marketed to the public. The FDA is continuously warning, fining and even prohibiting the sale of supplements and foods that make these claims. The major exception to this rule for many years has been veterinary therapeutic diets.

What is a therapeutic diet?
Therapeutic diets by their very definition are intended to diagnose or treat disease – they are diets to dissolve or prevent bladder stones, help slow the worsening of kidney disease, and diagnose food allergies, as examples. Depending on the disease being addressed, they may be very different from the diets you can buy at any pet store – they may contain levels of nutrients below what is legally allowed to be sold for a healthy pet, for instance. (NB: While many people call these diets “prescription diets”, this term is trademarked by the Hill’s company for their therapeutic diets and should not be used for those made by other companies.) Most of these diets have undergone extensive testing to prove their efficacy, yet the majority have not undergone the level of scrutiny that would be required for them to be sold as drugs. The FDA has gotten around their own regulations by providing an exception to these foods, so long as they are purchased through or with the permission of veterinarians. In this manner, they are allowing veterinarians to weigh the evidence and decide which foods to recommend for which pets and making them responsible for monitoring the pets that are eating these diets. Recently, however, the FDA has become concerned because a number of new companies are starting to market therapeutic diets directly to pet owners, without the involvement of a veterinarian. The FDA issued new guidelines on therapeutic diets in April to clarify their stance.

So getting back to what makes these diets special, what’s the big deal that they need to be fed under the supervision of a veterinarian? There are two reasons why it is critical to have veterinarians involved in making the diet decisions and monitoring their use:
1. Some of the diets have nutrient levels that while appropriate for certain diseases could be unsafe for healthy pets, as mentioned above.
2. If your pet has a health issue that warrants a special diet, it should be closely monitored by a veterinarian, even if the diet contains nutrient levels safe for healthy pets.

A great example of the first concern is diets designed for pets with kidney disease. These diets are generally lower in protein than is recommended for healthy animals and may be deficient in phosphorus for a pet with fully functional kidneys. While this nutrient profile has been shown in numerous studies to prolong the life of dogs and cats with kidney disease, it can lead to nutritional deficiencies and health issues in animals with normal kidneys.

An example of the second situation would be a pet that has a history of developing bladder stones. While most stone prevention diets are safe to feed to healthy animals, pets that develop stones should be closely monitored because the diets are not 100% effective and stones can block urine outflow and cause life-threatening disease. Some stones are caused by other health problems (such as liver disease or urinary tract infection) that cannot be corrected with diet. Another example would be a dog or cat with a suspected food allergy – many pet owners try to diagnose food allergies using diets purchased at the pet supply store and this frequently leads to false diagnoses and inappropriate management.

Why are the diets so expensive?
In general, therapeutic diets, while they may contain very common ingredients, have undergone extensive testing to ensure that they are appropriate for the disease for which they are recommended. Examples of testing for kidney diets includes feeding the diets to pets with kidney disease for many months and monitoring how they do compared to pets fed more typical diets with lots of bloodwork and other diagnostics. For diets for bladder stone prevention, the diets are fed to animals, their urine is collected and tested and the diet ingredients are then optimized to reduce risk of stone development. For pets with certain gastrointestinal conditions, fiber can be very important. The most accurate way to measure it in pet food is by analyzing for total dietary fiber; total dietary fiber can be as much as 3 times higher in a diet than the “crude” fiber measured for most diets. While total dietary fiber is typically available for therapeutic gastrointestinal foods, it is rarely, if ever, available in non-therapeutic foods due to the expense of the test (10-20x more expensive than crude fiber). Therapeutic diets designed for food allergies typically contain only the purest ingredients (such as proteins that have been cut up into tiny pieces to evade the immune system) and many are thoroughly tested to eliminate the risk of cross-contamination. Unfortunately, cross-contamination is extremely common in the “limited ingredient” diets that you can buy at any pet supply store.

As you can probably imagine, all of this testing can be VERY expensive – costing hundreds of thousands of dollars per diet, and these tests often need to be repeated every time there are any changes made to the diet. These costs must then be incorporated into the cost of the diets. It’s typically not the ingredients that make therapeutic diets expensive – it’s the science that goes into putting them all together.

Vets are NOT getting rich selling pet food
While many pet owners believe that veterinarians make a lot of money selling diets, this is not true. The mark-up on therapeutic diets is typically less than that of most regular pet diets; many veterinarians stock therapeutic diets more as a convenience to their clients than as a money-maker and it is common for pet owners to purchase these diets at online retailers or even at pet retail stores with a prescription, just like many drugs can be purchased from an outside pharmacy. Veterinarians want your pet to be healthy – if they recommend a therapeutic diet, it is because they think it will help your pet. If you have concerns, ask your veterinarian why they have recommended the diet and what makes the diet different from diets that you can purchase at the pet store.

Potential implications of the lawsuit
Back to the lawsuit – the cost of therapeutic diets, while high, is justified by the costs of developing and testing them. Keeping them under the control of a veterinarian protects pets and pet owners. If a lawsuit like this ends up going in the favor of the plaintiffs (the pet owners and their lawyers, which seems unlikely based on current FDA guidelines), it will only hurt pet owners and pets with medical conditions that could benefit from these diets. Forcing therapeutic diets to be approved as drugs or allowing them to be sold without the supervision of a veterinarian could mean that the companies can no longer recoup the money it takes to develop them (and may stop making them altogether!) or that new therapeutic diets could be marketed directly to pet owners with no testing (but certainly plenty of fancy advertising!) to ensure they fulfill their purpose. Either way, our pets lose!

Update: July 2017 – A federal judge ruled that the pet owner plaintiffs in the class action suit “failed to sufficiently allege that the pet food manufacturers were involved in price fixing”. The plaintiffs have until the end of this month to file an amended complaint.

Happy Feeding!
Cailin R Heinze, VMD, MS, DACVN


Dr. Cailin Heinze is a Board-certified Veterinary Nutritionist® and the Executive Director and Chief Academic Officer of the Mark Morris Institute, a non-profit organization whose mission is to promote optimal companion animal health by providing educational opportunities for veterinary students and veterinarians in clinical nutrition. She has also done some consulting work for Balance IT, a company that makes software and supplements for home-cooked pet diets. She is an expert in home-cooked diet formulation and general pet nutrition and has a special interest in feeding pets with kidney disease and cancer.

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