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t_Articles
Food fads may come and go, but the importance of a well-balanced diet
never goes out of style. One of the most important components of a
healthy diet is fibre. While it may not be the most exciting part of the
diet, eating foods high in fibre is essential for good health and
reduced risk of several diseases. This recommendation is as strong today
as it was more than 20 years ago when fibre hit the headlines after it
was noted that African tribes who took a diet high in fibre had lower
risk of several diseases. Scientific studies continue to produce new
evidence to support the need to increase fibre in the diet.
Dietary fibre is found only in plants. Dr Dennis Gordon, a researcher
in nutrition and dietary fibre at North Dakota State University in the
US, defines fibre as "Food carbohydrate that is not digested or absorbed
and which contributes to positive physiological functions in the body."
Soluble and Insoluble Fibre
If you've read up on dietary fibre, you may know that most
scientists classify fibre as either "soluble" or "insoluble". This
refers to whether the fibre dissolves in hot water. More importantly, it
helps to explain the different actions of the two types of fibre in the
body.
The largest amount of fibre in our diet is insoluble fibre. This type
of fibre provides texture to fruits, vegetables and cereals. Insoluble
fibre helps bind water in the intestine and increases the volume of
waste materials. The end result is more frequent and softer bowel
motions and less risk of constipation.
Soluble fibre is found in all fruits, some cereals (such as oats and
barley) and in legumes (dried peas and beans and lentils). This type of
fibre acts as a natural thickening agent in foods. For example, if you
add lentils or beans to a curry, they help to thicken the curry.
When we eat soluble fibre, it traps fatty substances in the
intestines thereby helping to prevent their absorption by the body. This
is thought to be the reason that soluble fibre helps to lower blood
cholesterol levels. Soluble fibre also has beneficial effects on blood
glucose levels.
Dietary Partners
The combined actions of soluble and insoluble fibre are
important in helping to maintain a healthy population of bacteria in our
large intestines. Fibre in the large intestine acts as a source of
energy for these bacteria to use. Fermentation of fibre in the large
intestine helps promote the growth of more lactic-acid producing
bacteria. A predominance of lactic acid producing bacteria helps to
prevent the accumulation of toxic and pathogenic (disease-causing)
bacteria.
How Much Fibre?
Most health organisations agree that adults should consume between 20
and 35 grams of dietary fibre a day. Yet most people in Asia fail to
reach this amount. According to the national dietary survey of
Singaporeans (1983), average fibre intake is just 15 grams a day. In
Hong Kong, a 1995 study estimated that fibre intakes averaged less than
10 grams a day.
Yet not only is it easy to increase fibre intakes, it's also vital to
good health. Dr Gordon warns, "There are many diseases or disorders
frequently related to inadequate consumption of dietary fibre. These
diseases include cancer of the colon, high blood cholesterol, diabetes,
diverticulosis and constipation."
Fibre and Health
Coronary heart disease is a leading cause of death in most Asian
countries including Singapore, Malaysia, China, India, the Philippines
and Indonesia. The National Heart, Lung and Blood Institute, US, has
reported a direct relationship between blood cholesterol concentrations
and premature coronary heart disease. Dietary fibre, particularly
soluble fibre, appears to lower blood cholesterol and may help to reduce
the risk of coronary heart disease.
Another disease that appears to be affected by fibre is colorectal
cancer, one of the most common forms of cancer in Asian countries.
Although the evidence is not yet complete, a lot of research has shown
that a low fat, high fibre diet may reduce the risk of this type of
cancer. Dr John Potter, Fred Hutchinson Cancer Research Center, notes
that, "Since 1970, a large number of case-control studies
have explored the role of dietary fibre in colorectal cancer, with
relatively consistent results suggesting a reduced risk with higher
consumption."
A study published in a recent issue of the New England journal
of Medicine reported that a high fibre diet did not appear to
affect the number of women in the test group who developed colon cancer.
However, there are many questions about the conclusions of the study. Dr
Potter suggests that a number of technical issues concerning this study
need to be resolved, including the translation of dietary intake
collected in the test group's questionnaires, biological questions about
fibre itself and questions intrinsic to epidemiological studies.
More research will undoubtedly be performed to determine what effect
dietary fibre has on colon cancer risk. Nevertheless, the overall
benefits of dietary fibre are widely accepted and dietary fibre remains
an important part of the diet. Drs Gordon and Potter both agree that
while one study alone will not prove a positive effect of dietary fibre
on any human disease, no one study deserves to be the final word in
dismissing the importance of dietary fibre for any disease.
There is no doubt that dietary fibre is beneficial to health, and
more research will continue to identify the areas in which dietary fibre
contributes to a healthy lifestyle.
FIBRE CLAIMS
The Food and Drug Administration (FDA) of the United States
of America, allows health claims relating to dietary fibre on food
labels. Several health claims have been authorised referring to the
effects of a high fibre, low fat diet in helping to lower the risk of
coronary heart disease and cancer. The FDA has recently approved
health claims relating to wholegrain foods and prevention of heart
disease and cancers.
In China, health claims about fibre on food packaging and in
advertising are allowed provided the claimed effect has been
scientifically proven. The studies to prove the efficacy of the
product must be conducted in China.
The situation is similar in Japan where foods making any sort of
health claim must be classified as "Foods for Specific Health Use" and
be subjected to rigorous testing of the physiological effects of the
product.
The Philippines follows a similar system to the US in allowing
health claims for certain food ingredients including dietary fibre.
In other parts of Asia, the whole area of health claims on food
products, including those relating to dietary fibre, is under
discussion.
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