The Colon Journal
A short course on the organ nobody taught you about.
Twenty-one chapters, in order, from where your food goes to why the last metre of your colon decides so much. No prior biology needed.
Fibre helps constipation.
The colon is an organ I never understood. Fibre is how I feed it.
Part 1
Meet your gut
Where food goes, what gets absorbed, and the one thing your body cannot break down.
The three organs your food travels through
By the end you will know which organ does what, and which one fibre is really for.
02What actually gets absorbed?
A short inventory of what your small intestine takes out, so you can see what it leaves behind.
03Why humans cannot digest fibre
The reason is a bond your enzymes cannot read, and it is where the word prebiotic finally earns a definition.
Part 2
The forgotten organ
Why the colon is a fermentation chamber rather than a waste bin, and who lives in it.
The colon is not a waste bin
Four jobs, only one of which is disposal, and why the slowest organ in your gut is slow on purpose.
05Meet your second digestive system
Not good bacteria and bad bacteria, but a workshop of specialists where one worker's output is the next one's raw...
06What is fermentation, actually?
Energy without oxygen, why gas is a by-product rather than a fault, and the one variable that decides comfort.
Part 3
What fermentation makes
Prebiotic, probiotic, postbiotic, and the short-chain fatty acids the rest of your body notices.
Prebiotic, probiotic, postbiotic
Three words used interchangeably that sit at three different points on the same pathway.
08The three short-chain fatty acids
Acetate, propionate and butyrate are not variations on one theme. Where each one goes decides what it can do.
09Butyrate: fuel for the colon
Your colon lining runs on a molecule your microbes make, and burning it maintains the conditions for making more.
10Your colon is not one place
Fermentation front-loads at the caecum and thins towards the sigmoid. Why the far end is the interesting end, and the...
11When the fuel runs out
Bacteria that run out of fibre switch to protein. What that produces, where it happens, and what carbohydrate fermentation suppresses...
Part 4
Why diversity matters
No single fibre does every job. What follows from that, and what a designed spectrum looks like.
No single fibre does every job
Solubility is one property out of four, and the only one on the label. Why two soluble fibres can behave...
13Speed is a design variable
Rate decides where a fibre ferments and whether it feels like anything. Why gas is a rate problem, and why...
14Who eats what
Bacteria can only ferment what they carry enzymes for, and most butyrate is made in two steps by two different...
15How to grade any fibre
Four questions that work on every product on the shelf, each mapped to a mechanism: applied to Buta-8 as well.
Part 5
The colon in daily life
Regularity, appetite, glucose, cholesterol, the gut lining: mechanism first, then honestly where the evidence stops.
Regularity, mechanically
Most of what fibre does for regularity is hold water where your colon would otherwise reclaim it.
17Fibre, appetite and GLP-1
Your densest population of appetite sensors sits at the far end of your gut, carrying receptors for the products of...
18Glucose and the viscosity brake
The one fibre effect with no biology in it, and why it only counts for the meal it is present...
19Cholesterol and the bile acid loop
A gel traps bile acids so they leave instead of being recycled, and the liver pulls LDL from the blood...
20The lining and the mucus layer
The barrier is a flow, not a wall. What bacteria eat when the fibre stops arriving.
21What we still don't know
Where the mechanisms stop predicting what will happen to you specifically, and which claims to be suspicious of, including ours.
Reference library
Shorter answers
Standalone pieces that answer one question directly. Not part of the reading order.