Dietary fibre, bowel function and health
The work reported in this thesis was designed to determine
the validity of the 'fibre-hypothesis' in western society.
Free living individuals resident in the United Kingdom were
the subject of investigation. Omnivores, vegetarians and vegans
were studied in order to ensure a wide range of fibre intakes and
the amount of fibre eaten ranged from 10 to 78 grams per day.
Disease pattern was assessed using a questionnaire.
Seven hundred and fifty people were matched for age, sex and
diet, and ten dietary groups were identified, ranging from
life-long vegetarians to life-long omnivores. The former group
in comparison with the latter, had a lower incidence, delayed
onset, lower severity and fewer disease associations. Many people
who increased their fibre intake by changing to a vegetarian diet
reported that the change to such a diet had relieved certain
disease symptoms particularly constipation.
Dietary intakes and parameters of bowel function including
transit time, stool characteristics: frequency, wet weight,
rheology and form, were measured in a sub-sample. Fifty-one
subjects were then matched for age, sex, diet, time of year and
health. In comparison with omnivores vegetarians ate significantly
more fibre, and this was significantly correlated with the measures
of bowel function. As fibre intake increased transit time
decreased, stool frequency and wet weight increased and stools
became softer and unformed.
The formed smooth cylindrical or snake-like stools of
vegetarians might be considered desirable and the associated
intake of about 40 grams of fibre daily a recommended amount.The achievement by omnivores of fibre intakes comparable to
those of vegetarians shows that drastic changes in eating habits
are not necessary in order to achieve this goal. If the goal is
achieved, the proportion of energy derived from complex
carbohydrate is increased at the expense of that from fat, thus
meeting major recommendations for a prudent diet.
The suggested intake is to be regarded as an interim
recommendation until more is known about variations in bowel
function, particularly faecal form, with time and endocrinological
phases in females.