Faecal matter is the solid or semi-solid remains of food that the small intestine could not fully digest or absorb. Bacteria in the large intestine further break down this material. Its formation is a fundamental biological process for eliminating waste.
What It Is Made Of
Human faecal matter is primarily 75% water and 25% solid material. The solid component includes approximately 30% dead bacteria and 30% indigestible food matter, such as plant fibers like cellulose.
Fats and inorganic substances, including calcium and iron phosphates, each make up about 10% to 20% of the solid content. Proteins account for roughly 2% to 3%. Other constituents include cellular lining, mucus, and bile pigments like bacterially altered bilirubin, which gives stool its brown color. Its distinct odor originates from volatile compounds like indole, skatole, hydrogen sulfide, and mercaptans, produced by bacterial action. Beyond bacteria, a gram of stool can contain billions of viruses, archaea, single-celled fungi, and human epithelial cells (colonocytes).
What It Reveals About Health
The appearance, consistency, and color of faecal matter offer insights into digestive health. Healthcare professionals use the Bristol Stool Chart to classify stool types. It categorizes stool into seven forms, from hard lumps to liquid. Types 3 and 4, a sausage shape with cracks or a smooth, snake-like form, are considered ideal for healthy digestion.
Stools classified as Type 1 or 2 (hard lumps or lumpy, sausage-like) often suggest constipation. Causes include insufficient fiber, dehydration, or certain gastrointestinal conditions. Conversely, softer, mushy, or liquid stools (Types 5, 6, and 7) indicate rapid transit or diarrhea.
Color variations provide clues. While brown shades are typical due to bile pigments, other colors signal dietary influences or health concerns. Green stool may result from leafy vegetables or rapid gut transit. Yellow, greasy stool suggests excess fat or malabsorption.
Black or bright red stool, if not due to specific foods or medications, may indicate bleeding in the upper or lower digestive tract, warranting medical attention. Pale or clay-colored stool points to issues with bile production or blocked bile ducts. Observing these characteristics helps identify potential digestive imbalances or when to seek professional advice.
Medical Uses
Faecal Microbiota Transplantation (FMT) is a medical procedure that uses healthy faecal matter for therapeutic purposes. It involves transferring stool from a screened donor into a recipient’s intestinal tract. Its goal is to restore a balanced gut microbiome, especially when disrupted.
FMT has proven highly effective in treating recurrent Clostridioides difficile infection (CDI), a severe gut infection often triggered by antibiotic use. Antibiotics deplete beneficial gut bacteria, allowing C. difficile to proliferate. By introducing a diverse microbial community, FMT outcompetes harmful bacteria and re-establishes a healthy environment.
The success rate for FMT in resolving recurrent CDI is approximately 90%. The transplanted microbes compete with C. difficile and restore gut metabolic functions, like bile acid metabolism, which inhibits C. difficile growth. FMT can be administered through colonoscopy, nasojejunal tubes, or oral capsules.
Its Role Beyond the Body
Beyond medical uses, faecal matter plays a role in natural ecosystems and has potential as a renewable resource. In environmental cycles, it is a component of detritus (dead plant and animal remains). Decomposers, such as bacteria and fungi, break down this complex organic matter, returning essential nutrients like carbon, nitrogen, and phosphorus to the soil, contributing to the biogeochemical cycle.
Faecal matter also indicates environmental monitoring, particularly for water quality. The presence of fecal indicator bacteria, such as Escherichia coli (E. coli), in water samples signals contamination from human or animal waste. While often harmless, their presence suggests more harmful pathogens may be present, indicating a public health risk.
Human faecal matter can be used for biogas production through anaerobic digestion, generating methane and carbon dioxide. This offers a renewable energy source and waste management method. Challenges include its lower methane yield compared to animal manure and the presence of ammonia, which can hinder the process.