Stool characteristics, including odor, can vary and are often temporary. This article explores common reasons why stool might have a garlic-like smell.
Dietary Factors
The foods consumed significantly influence stool odor. Certain foods contain sulfur compounds that, when broken down by digestive bacteria, produce distinct-smelling gases. Examples include garlic, onions, leeks, asparagus, and cruciferous vegetables like broccoli, cauliflower, cabbage, kale, and Brussels sprouts.
Other sulfur-containing foods are eggs, meats, some dairy products, and legumes such as soybeans and black beans. Spices like cumin and curry can also affect stool odor. As undigested food reaches the large intestine, gut bacteria ferment these components, releasing gases like hydrogen sulfide that create strong odors. The specific gases produced depend on an individual’s gut bacteria and the foods digested.
Influence of Medications and Supplements
Medications and supplements can alter the gut environment, affecting stool odor. Antibiotics, for instance, disrupt the balance of bacteria in the gut microbiome. This disruption allows other bacteria to multiply, changing stool characteristics and smell.
Iron supplements can also change stool odor. Unabsorbed iron interacts with gut bacteria, which convert it into iron sulfide, generating hydrogen sulfide gas. This gas, often described as a rotten egg smell, can contribute to a garlic-like odor. Additionally, supplements like glucosamine, chondroitin, or garlic itself contain sulfates that colon bacteria convert into sulfide gases. These effects stem from the medications’ influence on gut flora or nutrient absorption.
Medical Explanations
Medical conditions can result in unusual stool odors. Malabsorption syndromes, including celiac disease, Crohn’s disease, chronic pancreatitis, and cystic fibrosis, impair the body’s ability to absorb nutrients. When nutrients are not absorbed, undigested food reaches the large intestine, where it ferments and produces foul-smelling, often greasy and bulky, stools known as steatorrhea. These fatty stools may appear light-colored, soft, and can float or stick to the toilet bowl.
Small Intestinal Bacterial Overgrowth (SIBO) involves excess bacteria in the small intestine. These bacteria ferment carbohydrates, producing various gases, including hydrogen, methane, and hydrogen sulfide, which can alter stool odor. Hydrogen sulfide SIBO can result in a distinct rotten egg or sulfurous smell. Furthermore, viral, bacterial, or parasitic infections can affect digestion and lead to foul-smelling stool or diarrhea. Examples include Salmonella, Giardiasis, and Clostridium difficile, with the latter sometimes causing a strong or sweet odor.
When to Consult a Doctor
While variations in stool odor are often benign, certain accompanying symptoms warrant medical attention. It is advisable to consult a healthcare professional if a garlic-like stool odor persists or is accompanied by other concerning signs. These include severe abdominal pain or cramping, unexplained weight loss, fever, or chills.
Additional indicators for seeking medical advice include blood in the stool (red, black, or tarry), pus, or mucus. Persistent diarrhea or constipation, along with consistently fatty, greasy, or floating stools, also suggest a need for evaluation. A healthcare provider can assess these symptoms to determine the underlying cause if they last more than 48 hours or are severe.