Digestive · Intestinum crassum
Large intestine
Home to trillions of organisms that are not you, and that you cannot live well without.
- Length
- ~1.5 m
- Water reclaimed
- ~1.5 L / day
- Microbial cells
- Roughly comparable to your own cell count
- Transit time
- 12 to 48 hours
What it does
Reclaim water and electrolytes, host the microbiome, ferment what the small intestine could not break down, and store the remainder until it is convenient to leave.
The marvel
Your gut microbiome carries far more genes than your own genome does. These organisms ferment the fibre you cannot digest into short-chain fatty acids, and the cells lining your colon feed preferentially on one of them, butyrate. You are, in part, fed by your tenants.
How to serve it well
Screening is the whole ballgame
Colorectal cancer is among the most preventable cancers because screening finds and removes precancerous polyps. Guidance in many countries now starts at 45.
Feed the microbiome variety
Diversity of plant fibre sources is more consistently associated with a robust microbiome than any single supplement.
Limit processed and red meat
Processed meat is classified as a group 1 carcinogen by IARC, with colorectal cancer the best-established link. Dose matters.
Do not ignore a change in habit
A persistent change in bowel pattern lasting more than a few weeks is worth a conversation, particularly after 40.
Book an appointment
- A change in bowel habit lasting more than three weeks
- Blood in the stool, even if you think it is haemorrhoids
- Persistent abdominal discomfort or bloating
- Unexplained iron deficiency anaemia
Emergency, go now
- Heavy rectal bleeding
- Severe abdominal pain with fever
- Complete inability to pass stool or gas with a distended abdomen
What you may have been told
“Colonics remove pounds of impacted waste and improve energy.”
There is no evidence for autointoxication, the theory underneath colon cleansing. Documented harms include electrolyte disturbance, perforation, and disruption of the microbiome. The colon empties itself.
Where this comes from
- International Agency for Research on Cancer · Red and processed meat classification
- US Preventive Services Task Force · Colorectal cancer screening
- NHS · Bowel cancer symptoms
LUMEN is education, not medical advice, and it cannot know anything about you. It does not diagnose. If something here matches what you are experiencing, take it to a clinician who can examine you.