An unusually strong or distinct stool odor, especially one resembling cannabis, is a common concern. Stool odor results from complex biological processes in the gastrointestinal tract, and changes in diet or digestion can alter this scent. The odor itself is produced by a mixture of volatile organic compounds (VOCs) released as the body breaks down food.
The Chemistry Behind Stool Odor
The familiar smell of stool is primarily caused by microbial action in the large intestine. When undigested food components reach the colon, trillions of gut bacteria begin fermentation and putrefaction. This bacterial breakdown of dietary proteins and amino acids releases a variety of pungent gases and organic compounds.
Among the main culprits for foul odor are compounds like skatole and indole, byproducts of the breakdown of the amino acid tryptophan. Hydrogen sulfide, often described as a rotten-egg smell, is also produced when sulfur-containing proteins are metabolized. These volatile organic compounds create the characteristic, strong smell associated with human waste, and changes in their balance can produce distinct smells.
Dietary Sources of Cannabis-Like Compounds
The reason your stool might specifically smell like cannabis is most often attributed to terpenes, a class of aromatic molecules. Terpenes are volatile organic compounds responsible for the distinct scents of thousands of plants, including citrus, pine, herbs, and cannabis. These compounds are consumed regularly in many common foods and beverages.
Specific terpenes, like myrcene, pinene, and limonene, cause the earthy, musky, or pine-like odors associated with cannabis. Myrcene, for example, which provides an earthy and sometimes skunky note, is found in high concentrations in mangoes, hops (meaning it can be present in beer), and lemongrass. Pinene, which smells like pine needles, is abundant in rosemary, dill, basil, and certain nuts and citrus rinds.
When consuming foods rich in these terpenes, the body may not fully metabolize them in the small intestine. These undigested, aromatic compounds pass into the large intestine and are excreted in the stool, largely intact. This process releases the familiar scent, directly mimicking the odor produced by the same terpenes in the cannabis plant. A high intake of these terpene-rich foods is the most common explanation for the specific “weed-like” odor.
Digestive Efficiency and Transit Time
The speed at which food moves through the digestive tract, known as transit time, significantly influences the final odor of the stool. If food passes too quickly, it can lead to malabsorption and incomplete digestion. This rapid transit means the body has less opportunity to break down and absorb aromatic compounds like terpenes.
When digestion is rushed, more undigested food matter, including volatile organic compounds, reaches the colon. Gut bacteria then have a larger substrate to ferment, resulting in a higher concentration of pungent compounds in the stool. Conversely, a very slow transit time can also increase odor by allowing more time for bacteria to produce odor-causing metabolites.
A change in gut motility, due to stress, illness, or a shift in fiber intake, can alter the concentration of odor-producing compounds. Stool consistency also plays a role; looser stool associated with rapid transit tends to have a stronger odor due to the increased volatility of the compounds.
When to Consult a Healthcare Provider
While a cannabis-like odor is typically harmless and dietary in origin, a persistent change in stool odor alongside other concerning symptoms warrants medical consultation. These warning signs indicate that the digestive system may be experiencing more than a temporary change.
You should consult a healthcare provider if you experience:
- The presence of blood in the stool (bright red or black and tarry).
- Unexplained and unintentional weight loss.
- Persistent abdominal pain.
- A sudden, lasting change in bowel habits, such as chronic diarrhea or constipation.
- Stool that is consistently pale, clay-colored, or excessively greasy, which may indicate fat malabsorption.