What Foods Make Stools Darker? Your Guide to Dietary Causes

December 9, 2025 •

4 min read

According to health sources, a variety of dark-colored foods and supplements can temporarily and harmlessly change stool color. Understanding what foods make stools darker can prevent unnecessary alarm. While it is always wise to be aware of changes in your body, seeing a blackish or dark green stool can often be attributed to something as simple as your diet.

Quick Summary

Stools may become darker due to consuming certain foods and supplements, such as black licorice, blueberries, iron pills, or activated charcoal. The temporary change is typically harmless, but distinguishing it from other potential causes like GI bleeding is important.

Key Points

Dietary Factors: Dark foods like blueberries, blackberries, and black licorice can temporarily turn your stools a dark color.
Iron is a Cause: Taking iron supplements or consuming large amounts of iron-rich foods, like red meat and spinach, can result in black or dark green stools.
Medication Effect: Certain medications containing bismuth, such as Pepto-Bismol, and activated charcoal supplements are also known to cause black stools.
Distinguish from Melena: Dark, tar-like, and foul-smelling stool (melena) can signal internal bleeding and should be evaluated by a doctor, unlike the non-tarry changes from food.
Watch for Symptoms: If dark stools are accompanied by dizziness, weakness, or abdominal pain, seek immediate medical attention, as this is a sign of a serious issue.

Common Dietary Culprits

Changes in stool color are a common occurrence and often directly related to the foods and beverages we consume. Several items in your pantry and refrigerator can contribute to a darker, or even black, stool color. The effect is temporary and resolves once the item has passed through your digestive system.

Pigment-Rich Fruits and Vegetables

Natural food pigments are a primary cause of dark stool. When these pigments, like anthocyanin in berries, are not fully absorbed during digestion, they can exit the body via stool. The most common culprits include:

Blueberries and Blackberries: The deep purple and blue pigments in these popular fruits are a frequent cause of dark or black stools, and may also leave black flecks from the undigested skins.
Beets: Beets contain the powerful pigment betanin. While beets most famously cause reddish stools and urine, sometimes this can appear very dark, especially if combined with other darkening factors.
Dark Leafy Greens: Consuming large quantities of vegetables high in chlorophyll, like spinach and kale, can sometimes lead to very dark green or blackish stools.

Iron-Rich Foods and Supplements

Iron is a major contributor to dark stools, both from dietary sources and from supplements.

Iron Supplements: Oral iron tablets, used to treat or prevent anemia, are a very common cause of black stools. The unabsorbed iron oxidizes in the gut, turning the stool a dark green or black color. This effect is harmless but can be visually startling.
Red Meat: Eating large portions of red meat, such as beef or liver, which are high in iron, can also lead to stools with a darker hue.
Blood Sausage: As the name implies, this food item contains blood and can result in black stool upon consumption.

Beverages and Confections

Beyond whole foods, other items we consume can change stool color.

Black Licorice: The natural compounds used to create black licorice candy can be very concentrated and easily darken stool.
Dark Beer: Certain dark stouts and beers are known to darken stool.
Grape Juice: The dark pigment in grape juice, especially when consumed in large quantities, can cause a noticeable darkening effect.
Artificial Food Coloring: Foods or drinks with artificial black, blue, or purple dyes can also cause discoloration.

Medications

Certain over-the-counter medications also have a darkening effect.

Bismuth Subsalicylate: This active ingredient in products like Pepto-Bismol and Kaopectate combines with trace amounts of sulfur in the digestive system to create black bismuth sulfide.
Activated Charcoal: Taken for poisonings or as a supplement, activated charcoal is a black, powder-like substance that will naturally cause black stools.

Is it Food or Something Serious? A Comparison

To help you distinguish between a dietary cause and a more serious medical issue, consider the key characteristics below. It's crucial to remember that any persistent or tarry black stool should prompt a call to a healthcare provider.


Feature	Food/Supplement-Related Dark Stool	Melena (Upper GI Bleeding)
Appearance	May be dark green, dark brown, or black; typically solid and not sticky.	Dark black and shiny; has a sticky, tar-like consistency.
Odor	Normal or slightly different, but not particularly foul.	Has a distinctively foul, strong odor due to digested blood.
Duration	The color change is temporary and resolves within a few days of stopping consumption.	Can persist for several days, especially if the bleeding source is ongoing.
Associated Symptoms	Typically none, or only minor GI upset from supplements.	May be accompanied by abdominal pain, dizziness, weakness, or vomiting.

When to Seek Medical Attention

While most cases of dark stools are harmless, it's vital to recognize the red flags that indicate a more serious condition, such as bleeding in the upper gastrointestinal (GI) tract. Bleeding in the esophagus, stomach, or first part of the small intestine causes blood to mix with digestive juices, turning it black and tarry. This condition is called melena and requires immediate medical attention.

If your dark stools are accompanied by any of the following, contact a healthcare provider right away:

A sticky or tarry consistency
An unusually strong, foul odor
Abdominal pain or cramping
Dizziness or lightheadedness
Vomiting, especially if it contains blood or black, coffee-ground-like material
A history of liver disease or ulcers

Conclusion

Observing a change in stool color can be unnerving, but often the cause is as simple as what you recently ate or took as a supplement. Blueberries, beets, black licorice, and iron pills are common and harmless culprits behind dark or black stools. However, it is crucial to pay attention to the texture, odor, and any accompanying symptoms. If your stools are tarry, foul-smelling, or if you experience abdominal pain or dizziness, do not hesitate to contact a doctor for a proper diagnosis. Being aware of the visual differences between diet-induced changes and signs of potential bleeding is the best way to monitor your digestive health and ensure peace of mind.

For more information on differentiating between normal and pathological stools, see health resources like MedlinePlus.gov.

Frequently Asked Questions

Yes, blueberries contain strong natural pigments called anthocyanins, which can pass through your digestive system unabsorbed, resulting in dark blue or black stools.

The unabsorbed iron from supplements reacts in the digestive tract, causing the stool to turn a dark green or black color. It is a harmless and very common side effect.

Stool from bleeding (melena) is typically very black, sticky, and has a strong, foul odor. Food-related dark stools are usually not tarry and lack that distinct odor.

While beets are famous for causing red or pink stools, in some cases, the color can appear very dark or reddish-black, especially when combined with other darkening factors in your diet.

Medications containing bismuth subsalicylate, like Pepto-Bismol, can temporarily cause black stools by forming black bismuth sulfide in the stomach.

The color change from food is temporary and should resolve within 24 to 48 hours after stopping consumption of the dark-colored food.

No, consuming large amounts of dark leafy greens can cause a very dark green or blackish stool due to the high chlorophyll content. This is a harmless effect.