Articles of interest

Pescription dog food

Prescription Diets

Did you know that "prescription diet" is an unregulated marketing term? No prescription is required to buy these foods, nor do they have to meet any special requirements or get approval from the FDA or AAFCO.

Certain health conditions do require dietary changes, though prescription diets are not always the best option (they are often formulated based on outdated and disproved hypotheses). One example is Hill's Prescription u/d, prescribed for dogs prone to forming calcium oxalate stones. U/D is low in protein, calcium, phosphorus, magnesium, and potassium and high in carbohydrates. Newer recommendations for dogs prone to forming CaOx stones say that diets should not be restricted in protein, calcium, or phosphorus. One study found that canned diets with the highest amount of carbohydrate were associated with an increased risk of CaOx urolith formation, and concluded that “canned diets formulated to contain high amounts of protein, fat, calcium, phosphorus, magnesium, sodium, potassium, chloride, and moisture and a low amount of carbohydrate may minimize the risk of CaOx urolith formation in dogs.” My article on Calcium Oxalate Stones, published in the WDJ in May 2010, will be available on my web site in November 2010 (email me if you need help before that).

In other cases, no dietary changes are needed for health conditions for which prescription diets are used, or any necessary changes can be more easily and effectively done using regular commercial foods and/or supplements. Examples:

• No prescription diet is needed to treat struvite crystals, which are normal and do not require treatment (other than of any associated urinary tract infection). See my article on Struvite Stones & Crystals for more information.
• Hill's Prescription r/d and w/d are used for weight loss. These foods are high in carbs and low in fat. They are exceptionally high in insoluble fiber, primarily cellulose (sawdust), indigestible ingredients that supposedly help the dog feel full without adding calories. Studies have shown, though, that dogs fed diets that are high in protein and low in carbs, with moderate amounts of fat, are much better at helping dogs lose weight and feel satisfied than high-carb, low-fat diets. See Overweight Dogs above and my article on Weight-Loss Diets for more information.
• Hill's Prescription j/d, used for dogs with joint disease, primarily adds a small amount of fish oil, which provides omega-3 fatty acids. Fish oil breaks down when exposed to light, heat or air, so any fish oil added to dry food is likely worthless. It is simpler, cheaper and more effective to feed a better diet and add fish oil yourself. Flaxseed is also included, which provides a form of omega-3 fatty acids that is not well utilized by dogs. See Supplements for more information. J/D also adds a tiny amount of glucosamine, chondroitin and manganese. These Nutraceuticals can be helpful for dogs suffering from joint disease, but once again are best added separately to a higher-quality diet. See Supplements and Diet Guidelines for Dogs with Arthritis for more information.
• Hill's Prescription b/d, prescribed for dogs with canine cognitive function, is similar. It adds significant amounts of vitamin E along with microscopic amounts of carnitine and tiny amounts of vitamin C . It uses flaxseed to supply omega-3 fatty acids (I believe that their flaxseeds are not even ground, making them totally ineffective). Feed a higher-quality food and add fish oil and an antioxidant supplement to better achieve the goals of this food at lower cost.
• Dogs with liver disease do not need a diet change unless they are showing signs of hepatic encephalopathy or have a portosystemic shunt.
• A prescription diet is not needed for dogs with diabetes -- see the K9Nutrition FAQ for more info; also this article that concludes, "Consumption of diets with low carbohydrate, high protein, and moderate fat content may be advantageous for prevention and management of obesity, impaired glucose tolerance, and diabetes in cats and dogs."

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