THE ADVERSE AND BENEFICIAL EFFECTS OF DIETARY FIBRE ON HUMANS

The effects of dietary fibre on humans are both nutritional and physiological. In both cases the effects are either positive or negative.

THE ADVERSE EFFECTS 

The following adverse effects have been observed:

a. Decreased Absorption of Vitamin B12:-
It has been observed that too much intake of pectin from fibre may cause decreased absorption of vitamin B12.

b. Loss of Mineral Nutrients:- 
The effects of increased dietary fibre intake on retention of trace elements, iron, zinc, and copper have been relatively consistent in both human and animal studies.

This indirectly predisposes humans or animals to rickets and oesteomalacia.

c. Diarrhoea:- 
When someone is changing from a low to a high fibre diet, he/she is liable to abdominal discomfort. This is due to increased gas production in the colon.

Sometimes, the person experiences slight diarrhoea. All these symptoms are however, transient.

THE BENEFICIAL EFFECTS 

The beneficial effects of increased consumption of dietary fibre by far out-weigh the adverse effects. Some of these beneficial effects are as follows:

a. Reduces blood sugar levels for Diabetics:- 
High fibre diets level have proved to be of value to sufferers of diabetis mellitus.

Diets high in fibre slow down the release of glucose to the blood stream and in this way the symptoms of the disease are minimized.

b. Lowers Cholesterol concentration:- 
Studies have shown that high fibre diets can lower the concentration of cholesterol in some people's blood.

This may account for the statistical link between high-fibre diets and lower incidence of coronary heart diseases.

c. Sources of Harmless Energy:- 
Fibre are attacked and broken down by harmless bacteria which inhabit the colon and partly convert them(fibre) to short chain fatty acds, carbon (iv) oxide, hydrogen and methane.

The short chain fatty acids, mainly ethanoic, propanoic and butanoic acids are absorbed into the blood stream and may be used as source of energy.

d. Reduces Constipation:- 
It has been reported that one of the best physiological effects of dietary fibre is on relieving constipation by modifying transit time through the intestine, increasing bulk and softening the faeces via greater water retention.

Constipation arises from intake of low fibre diets. This in turn leads to difficulty in voiding with the consequent causation of "straining" disseases such as haemorrhoids and variscose veins.

e. Reduces Obesity:- 
Obesity related diseases are the commonest causes of death in some Countries.

Fibre reduces the energy intake of foods and thus reduces obesity which is caused by excessive energy intake.

Obesity predisposes people to a number of metabolic diseases such as coronary heart disease, and arteriosclerosis.

f. Prevention of Diverticular Disease:- 
This is the commonest disease of the colon. Low fibre diets lead to decrease in size of stool, increased transit time and makes the faeces stay longer in the colon.

This leads to pressure build up and the consequent ballooning of the wall of the colon. This is called diverticulosis. Infection of the diverticuli leads to diverticulitis.

Small fecal volume due to low fibre diets, allows excessive segmentation of the colon. This leads to building up of pressures which will eventually lead to formation of button-shaped diverticuli.

g. Prevention of Large Bowel Cancer:- 
Colon cancer is the most frequent type of cancer in North America and the second most common type in Britain.

Dietary fibre sweeps away poisonous substances (implicated as carcinogens) which are produced in the large bowel by the decomposition of bile salts.

h. Increases Satiety Value:- 
Low fibre diets are also claimed to have a low satiety. It is suggested that it is easier to over eat when the diet is refined.

In general, there should be dietary fibre intake in food supplements. It is equally important that clinicians and health care workers emphasize the highest level of fiber inclusion in human diets.


REFERENCES

Bengham, S. (1978). Dictionary of Nutrition, A consumer's Guide to the Facts of Food. Barris & Jenkins, London.

Fox, B. A. and Cameron, A. G. (1989). Food Science, Nutrition and Health. 5th ed. Edward Arnold; A Division of Hodder & Stoughton, London.

Onimawo I. A. (1995). Season Variations in Energy Intake, Expenditure and Body Composition of Students in a Nigerian College of Agriculture. Ph.D Thesis, University of Ibadan, Nigeria.