Keto Diarrhea: When Does This Unpleasant Side Effect Start?

The keto diet is a low-carb, high-fat diet that has become popular in recent years. While it may help with weight loss and improved blood sugar control, it can also lead to an unfortunate side effect: keto diarrhea. This condition is characterised by loose, watery stools and can be caused by several factors, including an increase in fat intake, a decrease in fibre intake, and changes in gut bacteria. Some people may experience keto diarrhea within the first few days of starting the diet, while others may not see any effects until weeks or months later.

High-fat content

The keto diet is a low-carbohydrate, high-fat diet. The basic idea behind the keto diet is to restrict carb intake so that the body switches from burning glucose (sugar) for energy to burning fat, including stored body fat and dietary fat. This shift in metabolism is known as ketosis.

The high-fat content of the keto diet can cause keto diarrhea. Fat takes longer to break down in the body than carbs or protein. When you suddenly start eating a lot of fat, your digestive system can struggle to keep up. Some of the fat may be malabsorbed—not broken down properly and, thus, not completely absorbed by your body—and excreted in your poop. This can lead to steatorrhea, a specific type of diarrhea caused by too much fat in the stool. Steatorrhea is typically pale, foul-smelling and might be coated in a thick, greasy film.

The time it takes for your body to adjust to digesting high amounts of fat can also cause keto diarrhea. This can lead to slight malabsorption diarrhea that usually resolves with time. As a registered dietitian, Johna Burdeos, explains, fat is typically harder to digest compared to protein and carbs, and takes longer as well. When following the keto diet, you're likely to consume a greater amount of fat than you normally would to compensate for restricting carbs.

To break down fat, the liver needs to produce bile. A diet high in fat requires the liver to release extra bile. As bile is a natural laxative, an excessive amount may push waste through the digestive tract quicker than usual, leading to diarrhea. The high-fat and low-carb content of the keto diet may also lead to other gastrointestinal symptoms, such as nausea and bloating.

If you experience keto diarrhea, there are a few things you can do to help relieve the symptoms:

• Drink more water and electrolytes: It is important to replace fluids lost due to diarrhea. Drinking water and sugar-free electrolyte beverages can help replace these fluids and any lost electrolytes.
• Eat more fiber: Fiber can help relieve constipation or diarrhea. Greens, cucumber, broccoli, and cabbage are some high-fiber foods that are suitable for a keto diet. However, be mindful that insoluble fiber, which turns to gel when mixed with liquid, is better for preventing diarrhea.
• Eat less dairy: As whole dairy products are high in fat, people starting on a keto diet may consume more of these than they previously did. This dietary change may reveal an intolerance to dairy, common symptoms of which are diarrhea, bloating, and gas.
• Ease into the diet: A sudden change in diet may disrupt the GI bacteria. Easing into a keto diet by slowly reducing carbs and increasing fats may help the body adapt better.
• Add probiotics and prebiotics: Taking a probiotic supplement or increasing the intake of probiotic- and prebiotic-rich foods may effectively support gut bacteria during a keto diet and reduce the GI effects of the diet.
• Eat fermented foods: Eating fermented foods, such as sauerkraut and kimchi, can help improve digestion, possibly reducing constipation or diarrhea.

Artificial sweeteners

When following a keto diet, people may consume more artificial sweeteners and sugar alcohols than usual as they seek low-carb alternatives to foods and drinks they previously consumed. For example, they may use sweeteners in tea and coffee instead of sugar. Many keto-friendly cereals, protein bars, and yogurts also contain sugar alcohols such as erythritol and mannitol.

These sugar-free substitutes are known to cause significant digestive distress, and sugar alcohols, in particular, have been shown to have a laxative effect, leading to diarrhea.

If you are experiencing keto diarrhea, it is worth examining whether you are consuming foods that contain sugar alcohols and artificial sweeteners, as the symptoms may be attributable to the fact that these compounds are not readily digestible.

To alleviate diarrhea caused by artificial sweeteners, it is recommended to reduce your intake of these substances and opt for unsweetened foods and drinks.

Gut microbiome changes

The keto diet can cause changes in the gut microbiome, which can lead to gastrointestinal problems such as diarrhea. Gut microbiota refers to microorganisms in the GI tract, mainly bacteria that are important for health in many ways, including helping the body break down food and absorb nutrients.

A 2019 study found that diets high in fat might cause inflammation of the digestive tract, a decrease in healthful fatty acids, and unfavourable changes in the gut microbiome. Some small studies have found that after three months on the ketogenic diet, the bacteria in the gut change, which could cause diarrhea in some people. If the body is not used to eating more fats, this could alter the gut bacteria, causing diarrhea and looser stools from poor digestion.

However, it is important to note that more high-quality research is needed to determine the exact effects of the keto diet on gut health. While some studies have shown that a keto diet may have positive effects on gut bacteria, others have found that it can lead to adverse changes in the gut microbiome.

If you are experiencing diarrhea while on the keto diet, it is recommended to seek advice from a healthcare professional, especially if the diarrhea is severe or lasts longer than a week.

Dairy consumption

If you are experiencing diarrhea when starting a keto diet, it is recommended that you reduce your dairy intake to see if this improves your symptoms. In addition, it is important to stay hydrated, increase your fibre intake, and consider taking a probiotic supplement to support your gut health.

It is worth noting that not everyone who follows a keto diet experiences diarrhea, and the severity and duration of symptoms vary. However, if your diarrhea is severe or lasts longer than a week, it is recommended that you consult a doctor.

Laxatives and anti-diarrhoeal medication

Laxatives are meant to induce diarrhoea by drawing water into the gut or by causing the muscles of the intestines to contract. However, laxatives can cause diarrhoea that is problematic if they are overused. Antacids containing magnesium may also cause or worsen diarrhoea.

There are several types of laxatives:

• Bulk-forming laxatives – these add “soluble” fibre to your stool, allowing it to absorb more water and create larger, softer stools.
• Lubricant laxatives – these coat the surface of your stools to make them more slippery and easier to pass.
• Stool softeners – these mix fluid into stools to soften them, making them easier to pass.
• Osmotic laxatives – these cause your intestine to hold more fluid, softening your stools and helping your bowel move them out.
• Stimulant laxatives – these cause your bowel to squeeze or contract to move your stools out. This type of laxative should not be used for more than a few consecutive days, as overuse can cause the bowel to lose its muscle tone and forget how to push out stool unassisted.

If you are experiencing diarrhoea, anti-diarrhoeal medications can be purchased over the counter without a prescription. These include:

• Loperamide (brand name: Imodium)
• Bismuth subsalicylate (brand names: Kaopectate, Pepto-Bismol) – this medication can also be used to treat an upset stomach.

Loperamide slows intestinal movement, allowing your body to absorb more fluid and produce more formed stools. Bismuth subsalicylate balances fluid movement in the intestines, reduces inflammation, and prevents bacteria and viruses that cause diarrhoea from growing in the stomach and intestines.

It is important to read the instructions on the medication label before taking any anti-diarrhoeal medication. If you have any questions, consult your doctor or pharmacist. Do not take more than the recommended amount, as this can be dangerous. Additionally, do not take more than one type of anti-diarrhoeal medication at a time, unless advised by your doctor, as they may contain similar active ingredients, leading to excessive medication intake.

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