History of Fibre
The necessity for fibre is not a new idea. In Ancient Greece, Hippocrates wrote of “This important substance”. In 1837, an American, Sylvester Graham, announced that wholemeal bread was the best natural food to aid digestion, and in 1883, Dr Allinson (whose name is still known for wholemeal bread) wrote about its benefits in scientific literature.
During the 2nd World War, more fibre had to be included in flour and bread after milling to make it more economical. It was noticed that people suffered less from diseases of the large intestine and constipation during this period. Hence it was recognized that fibre might cure or at least alleviate other problems such as diverticulitis.
Ten years ago, the Committee on Medical Aspects of Food Policy (COMA), recommended in their publication, “Diet and Cardiovascular Disease”, that the intake of dietary fibre in the daily British diet should be increased. A subsequent report in 1984 by the National Advisory Committee on Nutritional Education (NACNE) recommended an increase in dietary fibre to around 30 gm per day – from the average 12-15 gm eaten by most of the population.
These reports stirred a flurry of health education efforts and, together with media attention, the result is that the majority of the population today is at least aware of the importance of having sufficient fibre in the diet, although it still remains true that most people are not reaching the recommended daily intake.
Moreover, as we have entered the ’90s, scientific experts have begun to talk about fibre in a new language and with new definitions. So, have things changed and what are the new facts we need to know?
What is Dietary Fibre?
Fibre is a form of carbohydrate naturally present in foods of plant origin including cereals, fruit, vegetables, seeds and pulses.
Fibre is actually contained in the cell walls of plants and is the substance which provides structural support and enables the plant to stand upright. The greatest concentration of fibre is generally in the external surface of the plant eg apple peel, potato skin and the outer layer of brown rice or wheat bran.
Fibre values are often reduced by cooking, processing or refining. The dietary fibre of white plain flour is approximately 3.4g/100g compared to a typical value of 9.6g/100g for 100% wholemeal flour. Likewise, cooking fruit and vegetables reduces the fibre content eg on cooking an apple, its dietary fibre content may reduce from 1.8g to 1.5g. It reduces further if the apple is pressed into juice.
Fibre and Carbohydrate (or Starch)
Some forms of carbohydrate (or starch) are more easily digestible than others and when cooked, some become resistant to digestion. Some resistant starch is broken down by bacteria in the large intestine and it is thought that this may play a very important role in increasing faecal bulk. Hence, some of the benefits of high fibre compounds are now thought to be due to the consumption of starch. Fortunately, many foods rich in starch are also good sources of fibre, and so dietary advice has not significantly changed!
Types of fibre
There are two main types of fibre: Soluble and Insoluble.
Insoluble Fibre
Found mainly in cereals, especially in wheat bran and in the structural framework of fibrous fruit and vegetables. Insoluble fibre absorbs water and so acts as a bulking agent in the stomach. It should therefore be taken with plenty of fluid for maximum benefit. It increases the rate at which food passes through the intestine and so removes any toxic substances from the body more quickly. Its dense structure means it requires more chewing. This plus the resultant swelling in the stomach leads to a feeling of fullness and so eating insoluble fibre can help in slimming. Jordans Natural Wheat Bran, Granny Ann High Fibre Biscuits
Too little insoluble fibre can cause constipation. Diverticulitis, varicose veins and even hiatus hernia can result. Also, if waste matter stays too long in the bowel, infection and disease can develop.
Soluble Fibre
Can be partly digested and serves a different purpose in the body. Soluble fibre is present in most fruit, vegetables and pulses and in many grains, especially oats.
Soluble fibre delays the rate of absorption of nutrients from food and forms a gel so that food travels through the body more slowly. A major benefit of this is that it delays the uptake of sugar by the blood, allowing a moderate quantity of sugar into the blood over an extended period. It can therefore be valuable to diabetics. It also delays the onset of hunger, so can be of benefit to slimmers or those watching their weight.
Soluble fibre can bind with cholesterol and assist in its elimination from the body. Hence it can be of value to those at risk from developing coronary heart disease due to high cholesterol levels and to those with gall bladder disease.
Recent Discoveries – Fibre and Disease
Colon cancer is a disease against which it was often suggested that fibre itself offered protection, by speeding up the expulsion of toxic products from the digestive tract. More recently it has been suggested that it is the fermentation of starch by bacteria in the colon which provides the protective role.
Breast Cancer
A study undertaken in May 1993 by Dr Peter Baghurst of the Division of Human Nutrition, Adelaide, with Dr Thomas Rohan of the University of Toronto, showed a “highly significant reduction in relative risk” of women who ate a lot of bread, cereals, fruit and vegetables. Earlier work had already shown that diet can affect the levels of hormones in the body which are thought to play a role in the development of tumours in the breast.
Last year’s study supports the suggestion that foods rich in dietary fibre may be protective against breast cancer either through their effects on the recycling of the hormone oestrogen, or through the effects on the hormones of other compounds found in high fibre foods. Dr Cuzick, Head of the Department of Epidemiology at the Imperial Cancer Research Fund commented that it was thought that high levels of fat in the diet were an important factor in the development of breast cancer:
“This study is particularly interesting in suggesting that dietary fibre may be preventative. Dietary fibre is already known to have a role in the prevention of stomach and lung cancer, but the evidence regarding breast cancer has previously been more sketchy.”
Much Fibre
It is possible to have too much fibre in the diet. Too much fibre can lead to intestinal discomfort or dehydration. Fibre may also bind some of the other nutrients in the intestine, making then unavailable for absorption over time. Too much bulk in the diet could also reduce the total amount of calories consumed which, whilst it may be of benefit to those wishing to lose weight, can be a problem to the malnourished, the elderly and children. People with small appetites cannot always eat enough food to obtain their energy needs if the food is high in bulk, and high fibre foods should be given in moderation to younger children.
Similarly, if changing the diet to increase the fibre levels, it should be done gradually, as too sudden an increase can lead to an upset stomach.
High Fibre Recipe: Sticky Prune Cake
170g (6oz) Pitted Prunes 170g (6oz) raw cane sugar 170g (6oz) Vegetable Oil 4 beaten eggs 170g (60z) Natural Yoghurt 260g (8oz) Wholemeal Flour 1 tsp sodium bicarbonate 1/2 tsp mixed spice 1/2 tsp ground cinnamon 1/2 tsp ground nutmeg 1/4 tsp ground cloves
Topping: 75g (3oz) Natural Yoghurt 75g (3oz) raw cane sugar 25g (1oz) Honey 1 tsp Vanilla Essence
Cover prunes with cold water, bring to the boil and simmer for 10-15 mins. Roughly chop the prunes. Whisk sugar, oil and eggs until smooth. Mix flour, sodium bicarbonate, mixed spices, cinnamon, nutmeg and cloves. Combine prunes, sugar, oil and egg mixture, flour and spice mixture with the yoghurt. Bake at 180°C/350°F/Gas Mark 4 for 30 mins until golden. Heat sugar in honey and yoghurt until sugar is dissolved. Add vanilla essence. Prick top of cake and pour topping over while cake is still warm. Cool in cake tin. Makes 12 portions. (Prunes can be replaced with dates or raisins.)
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