Matcha, a finely ground powder of specially grown green tea leaves, has become a popular beverage worldwide, valued for its unique flavor and concentrated nutrients. A common question arises regarding a peculiar side effect: Can consuming matcha change the color of your stool to green? The answer is definitively yes, and this temporary change is a known, usually benign, physiological response.
The Role of Chlorophyll in Stool Color
The vivid green color of matcha is directly responsible for this phenomenon, stemming from its high concentration of chlorophyll. Matcha tea leaves are shade-grown for several weeks before harvest. This technique forces the plant to produce more chlorophyll, resulting in a dark, rich pigment in the final powder. Consuming matcha means ingesting the entire tea leaf, which delivers a substantial dose of this pigment into your digestive system.
Chlorophyll is a robust molecule highly resistant to digestive enzymes in the stomach and small intestine. The natural brown color of stool comes from stercobilin, a breakdown product of heme processed through bile. When a large volume of undigested green pigment from matcha reaches the large intestine, it can overwhelm the paler brown stercobilin. This temporarily results in a noticeable green hue, similar to consuming large amounts of dark green vegetables like spinach or kale.
How Digestion Speed Affects Pigment Breakdown
The precise color of stool balances the pigments consumed and the time allowed for digestive processing. The typical brown color appears when bile, a yellowish-green liquid, is broken down by intestinal bacteria during normal transit time. This bacterial action changes the bile pigments into the brown stercobilin.
Matcha influences this process in two ways, both related to transit time. Matcha contains dietary fiber and caffeine, both of which increase gut motility, speeding up how quickly waste moves through the intestines. When waste moves too quickly, bacteria have insufficient time to convert the green bile pigment into brown stercobilin. The combined effect of rapid transit and high concentrations of undigested chlorophyll results in a saturated green color in the stool.
When Green Stool Signals a Health Issue
While temporary green stool after consuming matcha is a harmless dietary effect, it is important to understand when this color indicates a health concern. If the green stool is diet-related, it should resolve within a day or two after discontinuing the highly pigmented food. A persistent green color not linked to food intake may signal a digestive issue causing abnormally rapid transit time, such as severe diarrhea.
Conditions that accelerate waste movement, such as intestinal infections caused by bacteria or parasites, can result in green stool because bile does not have enough time to fully brown. Certain medications, including antibiotics or iron supplements, may also cause a greenish tint. If the green color persists for several days, or if it is accompanied by other symptoms like fever, vomiting, or abdominal pain, consulting a healthcare professional is advisable.