Light-Colored Stools and Low-Carb Diets

Yep, a high-protein diet and stool color are connected. An unexpected potential side effect of low-carb diets is changes in your stool color. Fatty or high-protein diets can cause light-colored stools, and many people on keto diets experience poop changes as well. Here's what you should know.

Changing your diet can also change your stool color.
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What Changes Your Poop Color?

The Mayo Clinic explains that the color of your stool is typically influenced by two things: what you've been eating and the amount of bile in your digestive system. Bile is a fluid that helps your body digest and absorb fats and break them down into waste products to be removed from the body.

Various medications, health conditions and your diet can influence your stool color:

  • Green stool can be caused by diarrhea or a diet rich in leafy greens. Another potential cause is green food coloring.
  • Yellow stool or yellow diarrhea on keto may be a result of excess fat in your stool.
  • Black stool is potentially serious. The Mayo Clinic says it can be a sign of bleeding in your upper intestinal tract. Other potential causes include eating licorice, taking iron supplements or taking some over-the-counter diarrhea medications.
  • Red stool can be caused by bleeding in the lower intestinal tract, hemorrhoids, red foods such as beetroot and red food coloring.

Read more: Causes of Fresh Blood in Stool

High-Protein Diet Stool Colors

One potential side effect of a high-protein diet is constipation. Increasing your protein intake generally means decreasing your intake of carbs and therefore decreasing the amount of fiber you eat. Fiber helps absorb water and adds bulk to your stool, which keeps your digestive system running regularly. Too little fiber can cause constipation. If you're constipated, your stools may appear darker in color than usual.

If you're eating a diet high in fat, you may notice light-colored fatty deposits in your stool or experience yellow diarrhea while on keto. Having too much fat in your stool is called steatorrhea, and it's potentially a sign that your body is passing fat through your system without digesting it properly.

If the fatty deposits in your stool don't go away after a few days or weeks, maybe the ketosis and stool changes are not linked. In that case your doctor can conduct something called a qualitative fecal fat test, which counts the number of fat globules present in your stool. In some cases, steatorrhea can signal various medical conditions or malnutrition.

Read more: Your Quest for More Protein Might Just Lead to Constipation

Ketosis and Stool Changes

If you're following the keto diet, you'll be restricted to eating very few carbs per day — between 20 and 50 grams. For reference, the Dietary Guidelines for Americans, 2015-2020, recommends that adults ages 19 and over consume 130 grams of carbohydrates per day.

Generally, people following the keto diet hope to enter ketosis, which is when your body burns stored fats for energy. Signs that you're in low-carb ketosis include bad breath, diarrhea, headaches, a loss of appetite and nausea. The digestive symptoms of ketosis are usually temporary, though bad breath and body odor may be consistent.

Any major change in your diet can cause changes in your poop, but if you notice any long-term color or consistency changes in your stool, it's worth speaking to a doctor about.

Read more: Causes of Black Stool Color

Other Causes of Pale Stools

Aside from the link between ketosis and stool changes, there are a number of things that can cause your stools to turn a pale, light or clay color:

  • A biliary obstruction (the blockage of any duct carrying bile from your liver to your gallbladder or from your gallbladder to your small intestine) can cause pale-colored stools. In this instance, the pale stools indicate a lack of bilirubin, an orange-yellow waste product created during the normal breakdown process of your red blood cells. Potential causes of a biliary obstruction include gallstones, a traumatic injury, cysts, tumors or inflammation.
  • Side effects from medication. Some drugs can discolor your stool. In particular, over-the-counter diarrhea medications like Pepto-Bismol and some antacids can cause light stools, but the Mayo Clinic says this is a temporary side effect that will go away when you stop taking the medication.
  • Cholestasis of pregnancy. If you're pregnant and consistently experiencing pale stools, you may be experiencing a pregnancy-related liver problem that slows down or stops the flow of bile from your gallbladder. This is more common in the second and third trimesters of pregnancy, though doctors aren't exactly sure what causes it. Treatment options for cholestasis of pregnancy include medication and fetal monitoring, and the condition typically resolves itself within a few days of delivery.
  • Celiac disease, which is an autoimmune reaction to ingesting the gluten proteins found in wheat, barley, rye and triticale. According to the Celiac Disease Foundation, there are over 200 potential symptoms of celiac disease including fatigue, anxiety, constipation, joint pain and missed menstrual periods. One potential symptom of celiac disease is pale, fatty stools. The recommended treatment for celiac disease is cutting gluten out of your diet entirely and sticking to a strict gluten-free meal plan.
  • Hepatitis. According to Intermountain Healthcare, one symptom of Hepatitis A, B and C is stool that's light in color. Hepatitis is an inflammation of the liver, and viral hepatitis can be spread from person to person through sexual contact, sharing fluids, contact with infected blood and contaminated needles. Other symptoms of hepatitis include dark urine, a low-grade fever, stomach pain, fatigue, aching joints, jaundice and a loss of appetite. Hepatitis can be diagnosed by a blood test, and Hepatitis B and Hepatitis C can be treated with drugs. There is no known cure for Hepatitis A at this time.
  • Pancreatic cancer. The American Cancer Society lists light-colored stools as one potential symptom of pancreatic cancer. Other symptoms include jaundice, belly pain, nausea, vomiting, weight loss, blood clots and poor appetite. Treatments for pancreatic cancer include surgery, chemotherapy, radiation, ablation, immunotherapy and pain control.

If you do experience white or light stools, the Mayo Clinic recommends speaking with your doctor about what's going on.

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