Indigestible plant-based carbohydrate, some people call it ‘roughage'.
It will not digest in our digestive enzymes in our enteric system.
It is made up of cellulose, resistant starch, resistant dextrins, pectins and oligosaccharides etc.
All these are basically carbohydrate structures that are designed so that it can’t be broken down by stomach acids and digestive enzymes.
They survive the transit through the gut. They can be soluble or insoluble. A very small amount of the fibre consumed is fermented in the colon by certain bacteria. A by-product of this process are short chain fatty acids. Most of the fibre is passed out unchanged in the faeces.
Fibre is crucial for health (No experimental crossover trials with human beings that are peer reviewed has produced literature that has evidence to back this claim)
Fibre is crucial for regularity and regularity (no evidence as above)
Fibre reduces risk of certain diseases (no evidence as above, weak epidemiology shows a weak association but can not inform on cause)
The evidence to show constipation, bleeding, bloating and pain could be reduced when you took fibre completely out of the diet is here. Watch Dr Paul Mason and his clinical trial about fibre and the total lack of need for it. Proof in real people.
Some ‘experts’ claim we need fibre to feed the bacteria that make short-chain fatty acids for us. This is incorrect as butter contains short chain fatty acids, so they are easy to obtain. These SCFA are used by enterocytes for energy only after the conversion to ketone bodies.
Enterocytes use short chain fatty acids (SCFA) for energy to do what they do, they first convert the SCFA into ketone bodies so when you are in ketosis you know this is happening in your body.
You can get ketones directly from the liver too, rather than obtaining them from your gut.
Other experts who have studied fibre include; Dr Sarah Pugh
And finally Dr Zoe Harcombe
Zoë has a PhD in public health nutrition. She struggles to find anything that is being taught in 'conventional' nutritional worlds that is true or evidence based. Hence why she spent 2008-10 writing The Obesity Epidemic - 135,000 words blowing apart: the misapplication of thermodynamics to dieting; the notion that 1lb = 3,500 calories, let alone that a deficit of 3,500 calories will lead to a weight loss of 1lb; the Seven Countries Study and the subsequent change in our diet advice, which has caused the obesity epidemic; the role of exercise in obesity and much more. See her presentation by clicking the link below.