Dry Cat Food: A Popular Yet Controversial Choice
Dry cat food is the most popular form of food fed to domestic cats today. It’s convenient, clean, easy to feed, inexpensive, and available in high volumes. Until recently, dry food was considered the “best” option for cats. It was heavily advertised and widely recommended by veterinarians.
However, recent studies have shown that dry cat food may not be the best choice, especially when fed exclusively over long periods. In fact, diets based on dry cat food have been linked to chronic dehydration, urinary tract disease, and renal failure.
The Evolutionary Diet of Cats
Cats are descendants of true carnivores. Having evolved in the deserts of Africa, cats adapted to their environment by meeting their moisture needs solely through the moisture found in their prey. This natural diet contained at least 65% water, while commercial dry food contains no more than 10% moisture.
You may be wondering, “But what about supplemental water intake?” We all provide free-choice water to our cats, but how often do you see your cat actually drinking it? Cats drink water, but because drinking is a learned behavior, it cannot be relied on to meet the moisture requirements that dry food fails to provide. For over 40 million years, cats have not needed to rely on supplemental water.
The Impact of Dry Food on Health
As mentioned earlier, the natural diet of cats would contain around 70% water. To consume that much moisture from a dry diet, a cat would need to eat seven times as much food, or it may suffer from chronic dehydration.
By contrast, commercially prepared canned food contains 40-45% water, which, while not equivalent to a wild cat’s diet, is much better than dry food.
In addition to its low moisture content, dry food absorbs moisture from the stomach once ingested, causing further dehydration. Long-term, this chronic dehydration can lead to urinary tract diseases and renal failure.
Urinary Tract Issues and Chronic Dehydration
Although urinary tract problems in cats are not new, they are more frequent in cats fed primarily dry food. Feline Lower Urinary Tract Disease (FLUTD) occurs when struvite or calcium oxalate crystals form in the urine, leading to bladder blockages. Decreased moisture content in dry food reduces urine volume, which increases the amount of crystals in the bladder.
Treatment often involves increasing urine volume, which can be achieved with prescription diets or simply switching from dry to canned food. Cats that are switched to wet food have a lower incidence of bladder obstructions than those kept on a dry food diet.
Additionally, long-term reduced water intake and chronic dehydration can contribute to chronic renal failure (kidney failure) in cats. Renal failure is a progressive, terminal condition with no cure—only supportive care. The kidneys filter waste from the blood, regulate electrolytes, and concentrate urine. As kidney failure progresses, these functions diminish. Symptoms often don’t appear until 70% of kidney function is already lost.
The Role of Grain Proteins and Obesity
Grain proteins in dry food release more waste during digestion, increasing the workload for the kidneys. Aside from the dehydration and kidney issues, dry cat food is also linked to higher rates of obesity. In the wild, a cat’s natural diet contains only 1-2% carbohydrates. However, carbohydrates in commercial dry foods often make up 45% of the diet. Cats metabolize fats and proteins for energy, so most of these carbohydrates are converted into body fat, leading to obesity and hepatic lipidosis (fat in the liver).
Should You Switch from Dry to Wet Food?
Despite these concerns, does that mean you should throw away your 20lb bag of dry food and stock up on canned food? Not necessarily. Some adjustments to your cat’s feeding plan may go a long way toward promoting long-term health.
If your cat already has kidney or urinary issues, dry food may not be the best option, and canned food could even help manage their condition. For healthy cats, a mix of wet and dry food might strike a good balance between convenience, cost, and health.
Ultimately, if you’re concerned about the use of dry cat food or have any questions about your cat’s nutrition, your veterinarian will be the best resource for selecting the best diet for your cat’s long-term health.
