Constipation
Written by Natascha Wille
One of the first things many cat owners notice when switching to a raw diet is that their cat’s poop is smaller, firmer, and far less smelly. While this is often a welcome change, it can also raise concerns—some worry their cat might be constipated.
Feeding raw can come quite close to replicating the nutritional profile of a wild diet—what cats would naturally eat in their native habitat. But it’s not a perfect replica. The only way to truly mirror a natural feline diet is by feeding small whole prey. One of the biggest differences between a homemade raw diet and true prey feeding is the absence of fur.
Fur has no nutritional value, but it plays two key mechanical roles that are difficult to replicate in a homemade diet. First, when cats bite down on whole prey, the fur brushes against their teeth, helping to clean them and reduce plaque buildup. Second, fur acts as a natural stool bulker. Without it, stool volume on a raw diet tends to be much lower.
Unfortunately, fur is virtually impossible to substitute in a homemade raw food recipe—we simply can’t add hair or fur to the mix.
In his younger years, my cat Charlie hunted and ate wild Eastern Cottontail rabbits. The juvenile rabbits he mostly caught weighed up to 500 grams (about one pound), and he consumed nearly the entire animal. He always left behind the stomach, intestines, and cecum, as well as the feet. The head was often eaten. Otherwise, Charlie consumed the whole rabbit—skin, fur, and bone included. Notice how his teeth sink into the fur, wiping away plaque as he bites down.
The resulting scat is passed as small, dry pellets that are surprisingly light—almost like dense felt. Their contents are a crumbly mixture of digested bone, a large amount of hair, some grass, and even rabbit teeth.
Having evolved in the dry climates of Africa and the Near East, cats are exceptionally well adapted to conserving water. They don’t sweat and rarely pant. They concentrate their urine to a high degree and extract nearly all moisture from their faeces before elimination. Cats are so efficient at water conservation that they can survive entirely on the fluids contained in their prey. As a result, their faeces are naturally firm, pellet-like, dry, and typically off-white or yellowish in colour. The contents are crumbly and held together largely by hair—both from the cat and from prey.
Below is an image of scat from a wild African Wildcat (Felis lybica), courtesy of the Hoedspruit Endangered Species Centre in South Africa.
The following image is scat from a wild Scottish Wildcat (Felis silvestris grampia) courtesy of Highland Tiger (Royal Zoological Society of Scotland).
If your cats’ feces look similar to the above images, it is probably perfectly normal and your cat is not constipated.
Above: A scat study I conducted in 1998 with my own cats. The left column of images shows scat from cats eating frozen mice. The right column shows scat from the same cats eating my raw food, which also included psyllium husk. There was no difference.
Some cats do experience genuine constipation. Signs include restlessness, loss of appetite, vomiting, and repeated but unsuccessful attempts to defecate—these symptoms warrant veterinary attention. A vet can help determine the cause, which isn’t always diet-related, and prescribe appropriate treatment. This often involves an enema, medication, or the use of osmotic laxatives like Lactulose or PEG 3350.
For cats with recurring constipation, a as-needed dose of a laxative such as PEG 3350 (polyethylene glycol 3350, sold in Canada as “RestoraLAX”) is a reliable and very effective choice. It’s important to note that polyethylene glycol is not the same as ethylene glycol—commonly known as antifreeze—which is highly toxic and deadly to cats. While both are glycols, they differ in molecular size. The molecules of polyethylene glycol are too large to be absorbed by the body, which is precisely why it works: PEG acts as an osmotic laxative, drawing water into the bowel and into the stool, softening it and making it easier to pass.
Because it is not absorbed into the bloodstream and simply passes through the gastrointestinal tract, PEG is even considered safe for patients kidney disease. I’ve personally used it almost daily for years with one of my own cats, who developed constipation due to anatomical changes following a radical tail amputation. PEG is an odourless, tasteless powder, and only a small amount is needed to be highly effective. It is available at most drug stores. “Lactulose” may be a preferred choice for cats with kidney disease, because of it’s dual function as a PRE-biotic. Cats with chronic kidney disease often suffer a shift in gut microbes. An introduction of PRE-biotic like Lactulose can help restore populations of beneficial gut microbes. Lactlulose is available from your Veterinarian or Pharmacist without the need for a prescription.
Complications of Constipation
Constipation is often just a digestive problem, but sometimes its effects can extend well beyond the colon. Left unresolved, chronic constipation can contribute to complications involving the urinary tract and can negatively affect cats living with Chronic Kidney Disease.
Constipation and Urinary Tract Health
One frequently overlooked consequence of constipation is its effect on normal urine flow. The colon and urethra occupy a limited amount of space within the pelvis. When the colon becomes filled with large amounts of dry, retained stool, it can place pressure on the urethra and partially restrict the flow of urine from the bladder.
This mechanical compression may prevent the bladder from emptying completely, resulting in urine retention. Urine that remains in the bladder for prolonged periods gives naturally occurring minerals additional time to form crystals. In cats predisposed to feline lower urinary tract disease (FLUTD), incomplete bladder emptying may, therefore, contribute to the formation of struvite crystals.
Constipation and Chronic Kidney Disease (CKD)
Constipation is especially common in cats with chronic kidney disease. As kidney function declines, affected cats lose the ability to concentrate urine efficiently and often produce large volumes of dilute urine. This continual loss of water can leave them chronically dehydrated, even when they appear to be drinking more. To conserve fluid, the body compensates by reabsorbing more water from the colon, causing stools to become increasingly dry, hard, and difficult to pass.
Retained fecal material remains in the colon longer, allowing intestinal bacteria additional time to break down proteins and generate waste compounds. Some of these compounds may be absorbed into the bloodstream, increasing the burden placed on kidneys that are already functioning below capacity.
Among the treatments commonly used to manage constipation in cats with CKD, Lactulose deserves special mention. In addition to drawing water into the colon and softening stool as an osmotic laxative, Lactulose reaches the large intestine undigested, where it serves as a PRE-biotic food source for beneficial bacteria. The fermentation products produced by these bacteria help acidify the colonic environment, which may discourage the growth of bacteria associated with the production of potentially harmful waste compounds. For this reason, Lactulose is often considered particularly valuable for managing constipation in cats with chronic kidney disease.
Are there more natural alternatives?
Water: Adding more water to food to soften stools generally doesn’t work for cats. Their physiology is designed to extract the maximum amount of water from food and feces before elimination. While more water in the food will increase urine output, it also dilutes the calorie density of the food. This can lead to reduced overall food intake, which results in less stool volume—and potentially worsens constipation.
Increased food intake: Kittens are rarely constipated. They produce healthy bowel movements daily on a raw diet. Compared to adult cats, kittens eat much more in proportion to their body size to support growth. Similarly, active adult cats that consume more food to meet their energy needs also produce more frequent and larger bowel movements. Simply put: more food in = more poop out. In contrast, sedentary cats on calorie-restricted diets naturally produce fewer feces. It’s normal for some cats to defecate only every second or third day. When they do, stools may be drier due to prolonged water absorption in the colon.
Cat hair: If prey fur is an ideal natural stool bulker, then cat hair is a close second. Cats ingest plenty of their own hair while grooming, and this should not be discouraged. Excessive brushing or bathing may reduce this natural source of “fibre.” In healthy cats on a raw diet, hair typically passes through the digestive system without issue. These cats rarely vomit hairballs. Frequent vomiting, grass eating, or regurgitation, however, may indicate nausea, gastric inflammation or other underlying illness that a Veterinarian should investigate.
Bone: Feeding raw bones or ground bone can contribute to constipation. Although the indigestible collagen bone matrix may help create more stool bulk, the large quantity of bone needed to create a balanced diet and meet the correct Calcium : Phosphorus ration causes excessive Calcium intake which is likened to constipation.
Magnesium: Calcium may promote constipation, while magnesium can help relieve it. Magnesium supports smooth muscle function and helps maintain healthy gut motility. It also attracts water into the colon, softening stools. While essential in the feline diet, magnesium is often restricted in commercial foods due to concerns about urinary crystals, which may contribute to magnesium deficiency and related constipation.
Dry cat food: For those open to feeding a mixed diet, adding some dry food can help bulk the stool. As long as raw or wet food remains the primary diet, feeding some dry food may help keep cats regular without exposing them to the risks associated with feeding exclusively dry food—namely, obesity, chronic dehydration and increased risk of urinary or kidney issues. That said, a diet made up solely of dry food can cause constipation. Dry diets often lead to chronically low moisture intake and produce hard, bulky stools that are difficult to pass. Some cats will begin to avoid defecation altogether, increasing the risk of megacolon.
Raw liver and fat: Raw liver has a mild laxative effect. Increasing the fat content in a homemade diet can help speed up gastrointestinal transit and encourage regular elimination. Vegetable oils mild in flavour like canola or sunflower oil may also help. Some cats enjoy olive oil and will lick it up straight. Vegetable oils are less digestible for cats and may act similarly to petroleum-based laxatives.
Pumpkin: Canned pumpkin is one of the most popular home remedies for feline constipation. Results are mixed. It contains about 90% water and 2.8% fibre, according to USDA data. So while it adds moisture, the actual fibre content is quite low. It may not bulk the stool, but it seems to have a mild laxative effect for some cats. However, this effect often wears off over time. Some cats accept foods with pumpkin added, but others may reject it.
Ground sunflower seeds: These are a gentle and nearly flavourless option for bulking stools. They pass through the cat’s digestive system mostly unchanged and can be easily ground into a powder with a coffee grinder before being added to food.
Ground flax seeds: Use with caution. While popular as a fibre source for humans, raw flax seeds contain cyanogenic glycosides that can release toxic hydrogen cyanide in the presence of water. The longer flax sits in moisture, such as raw food, the higher the toxin concentration. To make flax safe, boil it first or add it fresh just before feeding. Boiled flax also becomes gelatinous, which can improve food texture and add moisture to stools. Alternatively, use defatted, pre-treated flax fibre supplements.
Psyllium husk: Commonly sold as Metamucil, psyllium is often recommended for cats with constipation. It may be helpful short-term, but tends to lose effectiveness with prolonged use. Cellulose gums work similarly and may also lose effect over time. In our observational research, long-term inclusion of Psyllium husk in the diet eventually lead to an increase of hair ball regurgitation, or regurgitation of stomach fluids containing residual Psyllium husk. We are not sure of the actual underlying reason, but these symptoms are similar to those observed in association with irritation of the stomach.
Bran: Bran from wheat, oats, or rice is a well-known fibre source, but not an ideal one for cats. Wheat and rice bran are poorly palatable, and oat bran is high in starch. In cats, bran can cause regurgitation, gas, vomiting, or diarrhea. I would not recommend it.
Do cats need fibre? Fibre is not considered essential for obligate carnivores like cats. Their natural diet includes no plant fibre, and their digestion does not rely on fermenting bacteria. Fibre is important in the diets of omnivores and herbivores, but not carnivores. Introducing fibre and starch creates an environment in the gut for bacterial growth, which may cause fermentation, gas, and inflammation. Inflammation can lead to loose stools or diarrhea. Excess fibre may also reduce nutrient absorption and displace essential nutrients.
