Foods That Can Cause Dark Stool
Health ConditionsDigestive Health

Foods and Supplements That Can Turn Your Bowel Movements Dark

Foods and Supplements That Can Turn Your Bowel Movements Dark
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Updated on July 31, 2025
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Stools that appear very dark in color can be alarming. But a change to the color of your poop doesn’t necessarily indicate a serious health problem, and in many cases it’s caused by something you ate.

Let’s take a look at some foods and supplements that can potentially turn your bowel movements dark.

1. Iron Supplements

A common culprit behind color changes in bowel movements is iron supplementation.

Iron supplements can cause stool to become dark, and even black.

 If you are being treated for iron-deficiency anemia or are pregnant and taking prenatal vitamins that are high in iron, you may have darkened stools. It’s a common side effect and is generally harmless.

2. Antacid Medications

The medication bismuth subsalicylate (found in Pepto-Bismol and Kaopectate, among others), which is used to treat diarrhea, indigestion, heartburn, and nausea, may turn your stool black.

 In some people, these medications can lead to lighter white or clay-colored stools as well. These medications can even turn your tongue black. Again, this is usually a harmless side effect that should resolve after you stop taking the medicine.

Taking activated charcoal, which is sometimes used as a home remedy to treat heartburn, may also cause a dark stool.

3. Colorful Foods

While it’s certainly a good idea to “eat the rainbow,” don’t be alarmed if your healthy habits show up in your stool.

Dark leafy greens can cause stools to be tinged with green pigment, while tomato products, beets, cranberries, and red gelatin may lead to stools with a bright red hue.

Black licorice, blueberries, and blood sausage can darken stools to almost black.

 Artificial food coloring, common in drink mixes or ice pops, can also tint your poop a range of colors, from red to green.

It Might Be Because You Have Diarrhea

If you are experiencing diarrhea, your stools may be greener or lighter than usual, regardless of what you’ve been eating. That’s because bile, a fluid your liver produces to digest fat, starts off as a yellow-green color.

As bile travels through your digestive system, its pigments are chemically altered by enzymes and change from green to brown, which is why normal stools are generally brown. But when you have diarrhea, food is moving through your system so quickly that bile doesn’t have time to turn brown, resulting in green-tinted and lighter stools.

When to See a Doctor

While there are many foods that can cause dark stools, a change in color can also indicate an underlying medical condition, including a peptic ulcer, gastritis, and even certain cancers.

Stools that are brown, tan, yellow, or green are typically normal. But stools that are black, red, or white may indicate a problem.

“Black stool or bright red stool (in any amount — specks, streaks, etc.) should prompt medical attention,” says Lindsey Albenberg, DO, an attending physician in the division of pediatric gastroenterology, hepatology, and nutrition at the Children’s Hospital of Philadelphia.

If you haven’t eaten any foods or taken supplements recently that would cause this change in stool color, it’s important to talk to your doctor.

Along with noting blood in your stool, other warning signs that merit a trip to a healthcare provider include vomiting blood or feeling dizzy or lightheaded.

The Takeaway

  • Certain foods and supplements, including iron pills, antacids, and colorful foods, can cause your stool to turn dark, but it is generally a harmless side effect.
  • If you experience unexplained black or bloody stools, it’s important to consult with a healthcare professional to rule out serious conditions like gastrointestinal bleeding or a peptic ulcer.
  • While many cases of colored stools are normal, if you experience additional symptoms like lightheadedness, dizziness, or vomiting blood, see your doctor right away.
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Taking Iron Supplements. MedlinePlus. July 8, 2023.
  2. Stool Color: When to Worry. Mayo Clinic. October 10, 2024.
  3. Side Effects of Pepto-Bismol. National Health Service. August 3, 2025.
  4. Black or Tarry Stools. MedlinePlus. June 11, 2024.
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Yuying Luo, MD

Medical Reviewer

Yuying Luo, MD, is an assistant professor of medicine at Mount Sinai West and Morningside in New York City. She aims to deliver evidence-based, patient-centered, and holistic care for her patients.

Her clinical and research focus includes patients with disorders of gut-brain interaction such as irritable bowel syndrome and functional dyspepsia; patients with lower gastrointestinal motility (constipation) disorders and defecatory and anorectal disorders (such as dyssynergic defecation); and women’s gastrointestinal health.

She graduated from Harvard with a bachelor's degree in molecular and cellular biology and received her MD from the NYU Grossman School of Medicine. She completed her residency in internal medicine at the Icahn School of Medicine at Mount Sinai, where she was also chief resident. She completed her gastroenterology fellowship at Mount Sinai Hospital and was also chief fellow.

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Maya Dusenbery

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Maya Dusenbery is a journalist, editor, and author of Doing Harm: The Truth About How Bad Medicine and Lazy Science Leave Women Dismissed, Misdiagnosed, and Sick.

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