Dietary fiber: is it ineffective or even harmful?

Dietary fiber - cereal

Ineffective fiber

Many researchers believe that consumption of fiber decreases the risk of colon cancer. However, studies of some 88,000 women at the Harvard School of Medicine have not shown any statistical relation between the presence of fiber in the diet and the incidence of colon cancer or adenoma. 1

Fibre theory and carbohydrates theory

Many years ago scientists found that a diet containing a large amount of animal fat led to heart diseases. As a result, animal fats were replaced with carbohydrates. Many products containing mainly white flour and sugar began appearing. Thus the trend to decrease the amount of fat in the diet led to the increased consumption of refined carbohydrates and a corresponding decrease in fiber consumption. These changes in dietary habits caused an increase of diabetes, obesity, digestion problems and heart diseases. This gave rise to the theory that all these disorders had been caused by a simple lack of fiber and that they would be prevented by the reintroduction of fiber into the diet. Other researchers claim that the real reason was the increase in carbohydrates consumption, especially of refined/highly processed carbohydrates, i.e. those with a high glycaemic index.

Harmful effects?

Konstantin Monastyrski, in his book ‘Fibre Menace’ (2005) is very critical of fiber. He believes that fiber interferes with the digestive processes in the stomach causing the retention of ingesta in the intestines which in turn may lead to gastro-oesophageal reflux, stomach infections, stomach ulcers, intestinal infections, constipation, Irritable Bowel Syndrome, Ulcerative colitis or Crohn’s disease. Monastyrski points to fiber as the cause of diseases which other researchers believe fiber prevents, such as haemorrhoids.

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  1. 1. Fuchs CS, Giovannucci EL, Colditz GA, Hunter DJ, Stampfer MJ, Rosner B, Speizer FE, Willett WC (1999) Dietary fiber and the risk of colorectal cancer and adenoma in women. N Engl J Med. 340(3):169-76. PMID: 9895396