Digestive Health

10 February 2009

Eating your way to a healthy colon

The colon is an important part of the human body, and at present, the focus of intense interest. Learn more about this previously neglected part of the digestive tract.


The human colon is an important part of the human body, and at present, it appears to be the focus of intense interest. It is of the utmost importance to know more about this previously neglected part of the digestive tract. Your health depends on it.

Functions of the colon
The large intestine, which consists of the caecum, colon and rectum, is approximately 1,5 m long. It is responsible for the reabsorption of many nutrients and water, and ensures normal defecation. The colon is the site where most of the absorption of water, salts and vitamins synthesised in this organ by thousands of microorganisms, takes place.

Some food components, such as dietary fibre and oligosaccharides, which escape digestion in the upper parts of the digestive tract, are exposed to bacterial digestion in the colon. The colonic microflora, as these 'good' microorganisms are called, not only digest otherwise indigestible food components, but also manufacture a variety of significant vitamins which can be utilised by the human body.

Vitamin synthesis
The microflora of the colon synthesise the following vitamins:

  • Vitamin K - essential for blood clotting
  • Vitamin B12 - prevents pernicious or megaloblastic anaemia
  • Thiamin (B1) and riboflavin (B2) - play an important role in most metabolic processes (energy release), keep the nervous system functioning optimally and help to lower homocysteine levels, which are implicated in heart disease

After synthesis, these vitamins are absorbed through the wall of the colon for use in the human body.

Production of SCFAs
The microflora of the colon also ferment otherwise indigestible food components to short-chain fatty acids (SCFAs). The SCFAs provide fuel for the colonocytes (cells of the colon) and help with the absorption of water and salts.

The colon and its microflora also help to boost immunity. Recent research has shown that a healthy population of various microorganisms, such as Lactobacilli, and Bifidobacteria, can contribute to general health and increase our resistance to various infections (Candida, Salmonella, Escherichia coli).

Cholesterol-lowering function
Research has demonstrated that diets rich in soluble fibre (pectins from fruit, and hemicellulose from fruit, oats, legumes and psyllium) are capable of lowering raised blood cholesterol levels.

Two theories have been suggested to explain this finding: either the soluble fibre in the colon binds bile acids, which are produced by the gall bladder, so that additional cholesterol has to be used up to produce more bile acids, or the microflora in the colon ferment the soluble fibre to SCFAs, which inhibit cholesterol production in the body.

What does a healthy colon require?
A healthy colon requires the following nutrients:

  • Plenty of soluble dietary fibre - fruit, oats, legumes (dry beans, peas, lentils and soya products) to bind bile acids and lower blood cholesterol levels
  • Plenty of insoluble dietary fibre - wheat bran and other wholegrain products - to promote regularity
  • Oligosaccharides - Jerusalem artichokes, asparagus, onions, garlic, and mushrooms, plus neutraceuticals (foods enriched with inulin and other oligosaccharides), which promote the viability of colonic microflora
  • Microflora supplements, which contain Lactobacilli or Bifidobacteria, to increase the number of ‘good’ bacteria in the colon
  • Yoghurt and fermented milk products, which contain live Lactobacilli - also to promote healthy microflora
  • Water to help dietary fibre swell up and promote peristalsis to regulate bowel movements

Factors that disturb the health of the colon
Colon health is relatively easily disturbed by any of the following factors:

  • Diets with a low fibre content consisting of highly processed starches, protein and fat
  • Antibiotics, which destroy the microflora
  • Excessive stress
  • Infections causing diarrhoea
  • Use of harsh chemical and herbal laxatives

These factors, alone or in combination, can either destroy the microflora thus allowing harmful bacteria and yeasts (Candida) to take over and proliferate, or damage the normal peristalsis of the colon. – (Dr I.V. van Heerden, DietDoc)

More questions? Ask DietDoc


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Digestive Health Expert

Dr. Estelle Wilken is a Senior Specialist in Internal Medicine and Gastroenterology at Tygerberg Hospital. She obtained her MBChB in 1976, her MMed (Int) in 1991 and her gastroenterology registration in 1995.

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