THE POTATO AS A SOURCE OF FIBRE IN THE DIET J, F. Flynn*, S. F. O Beirn and D. P, Burkitt
Department et Surgery, Regional Hospital, Galway. Summary WENTY-FIVE of 48 volunteers mainT r a i n e d a daily intake of potatoes approximating to l k g for a minimum of 10 weeks and maximum of 90 weeks. The average consumption was O.86kg, i.e. about 21bs, containing an estimated 4.26g crude fibre (C.F.). C.F. intakes, intestinal transit times, . daily stool weights, COlD-rectal pressures, total body weights, and blood lipid levels were measured before, during and after comptetion of the trieI. In subjects inib ially consuming less than C.F. 59 daily there was a significant decrease in intestina; transit times and in colD-rectal pressures, and significant increase in stool weights. In subjects consuming more than C.E 5g daily, favourable changes in all of these parameters were recorded but they only reached significant levels in increased stool weight. Blood lipid levels were not altered and in spite of the high intake of potatoes, there was no increase in body weight. Introduction Evidence is accumulating that many diseases characteristic of modern Western civilization may be attributed in part to a deficiency of fibre intake (Burkitt and T r o w e l l 1975). Both diverticular disease (Painter and Burkitt, f975), and ischaemic heart disease (Trewell, 1973) have been shown to be closely associated with law-fibre diets. The experience of clinicians in the West of Ireland suggests that both of these diseases were still uncommon here until after the t93945 war, Preceding this period there had
been a progressive reduction in potato consumption accompanied by an increasing demand for foods containing sugar and white flour, and this trend has continued down to recent times (Brown et al., 1970). In view of these observations and the fact that trials conducted to estimate the effect of fibre on intestinal behaviour, stool characteristics, and body lipids have been almost entirely limited to cereals (Painter et al., 1972; Heaton, 1973; Hinton et a/., 1969) it was decided to study the physiological effects of increasing potato intake. At present the average daily C.F. intake from all sources (total C.F. or T.C.F.) in Connecticut, U.S.A. has been assessed as about 3.5g (Dodlrlan et al., 1976). This is about one-sixth that of rural Africans who are minimally affected by modern Western diseases (Lubbe, 1971). In 1860 the starchy daily C,F. intake in England and Wares alone was estimated to have been about 2.6-3,79 with T.C.F. 4.f -5.2g. These figures declined in 1979 to starchy C.F 1.4g and T C F 4.1g (Trowell, 1976) It was therefore de~ided ~o estimate the effect of approximately doubling the T.CF. intake, but using starchy Iced which allegedly has more effect in human physiology than that derived from fruit and green vegetables. One kg of potato contains approximately C F 5g. Subjects and Methods Forty-eight apparently normal volunteers were evaluated before the trial.
*Present address : Dept. of Thoracic and CardJovascular Surgery, Arhus, Kommunehospital, 8000 Arhus C., Denmark 285
286
IRISH JOURNAL OF MEOICAL SCIENCE
One of US (J,F.) discussed in detail each volunteer's daily food intake. The appropriate amount of each C.F. containing food was then selected and weighed. From this, by using standard values obtained from the American Board of Food and NJ.ltrition, the daily TC.F. intake together with the amount derived from potato was calculated for each volunteer. Intestinal transit times, daily stoo] weights, colo-rectal pressure, total body weights and blood lipid levels were now measured. Each subject was then requested to consume approximately l k g of boiled or baked potatoes a day for a minimum of 10 weeks, At the end of this period all studies were repeated. No restrictions were placed on the volunteer's diet otherwise. He was free to eat what he chose apart from the requested amount of potato. Twenty three completed the trial. The main reasons for defaulting were difficulty in attaining the required potato imake, dislike of pressure recordings or dislike of stool collectiQn. All subjects were urban males aged 20-56 years from a variety of occupations including hospital staff, army personnel, students and business men. Five of the 23 were found to be consuming what by Western standards was a substantial amount of C.F., i.e. over 5g daily on average. The remaining 18 (78 per cenf) were consuming less than 5g CF. daily, with an avers.ge of 3.5g. This figure approximates closely to present British and Connecticut standards which are thought to be deficient in fibre. For the purpose of calcutating results, therefore, it was decided to constitute a Group I (5) of those consuming more than 5g C F, daily and a Group II (18) of those consuming less than 5g C.F. daily. The age range in each group was similar. Transit times were studied by the method of Hinton (Hinton e t a l . , 1969) using barium impregnated pellets of the same specific gravity as the bowel contents. Twenty-five peltets were ingested
and the time ~(aken for 80 per cent of these to be passed was recorded. In order to exclude the possibility that a substantial part of this change in transit times occurred in the stomach and smag b o w e l a separate study was undertaken in which mouth-to-caecum fransd time was measured in 10 subjects by means of an image infensifier following ingestion of barium peilets. This transit t~m8 was studied on normal diet and after two wesks on a high potato diet. The mean pre-diet mouth fo-caecum transit time was seven hours, whilst on the potato diet it was six hours. Any change in total transit time was therefore concluded to be effectively a change in colo-rectal transit time. Bowel pressures were measured in the rectum and sigmoid colon using open tipped catheters linked to Stathem transducers (PD 23} with a write-out on a Devices M 19 recorder Recordings obtained were analysed according to the method of Smith (Attisha and Smith, 1969). ReSults Increased potato consumption was associaled with large stools which tended to be soft, and. unformed, but not loose, and which were easily evacuated, Table I shows the average daily tota] C.F. intake before and during the trial, and also the CF. intake derived from potato. Table II shows that stool weights increased signilicantly in both groups, but particularly in Group Ih The number of stools weighing over 200 g per day is
Group I II
Period Before During Before During
Crude fibre grams/day Total 5,6 SD -1=0.628 73 SB= I 0.758 355 SB= • 66 SD-- +0.49
Potato 2.1 41 1.0 43
THE POTATO AS A SOURCE OF FIBRE rN THE DIET also significantly increased in both groups Transit time was not shortened significantfy in Group I but was in Group II. Table Ill shows that mean peak heights and waves greater than 50 cm H=O and motility index were all significantly reducec~ in Group II, but not in Group L
287
l~iscusslon mid Conclusions This trial has demonstrated that potatoes c a n alter intestinal behaviour, increasing stool weight, r e d u c i n g transit time and reduci~lg colo-rectal pressures. The most striking effect of the potato diet was seen in Group II (78 per cent of those c o m p l e t i n g trial). All three main
TABLE II Group
Stool weights
I
200gin
Transit
Beore
149 SD~45
0
46
During
249 SD• P
Department et Surgery, Regional Hospital, Galway. Summary WENTY-FIVE of 48 volunteers mainT r a i n e d a daily intake of potatoes approximating to l k g for a minimum of 10 weeks and maximum of 90 weeks. The average consumption was O.86kg, i.e. about 21bs, containing an estimated 4.26g crude fibre (C.F.). C.F. intakes, intestinal transit times, . daily stool weights, COlD-rectal pressures, total body weights, and blood lipid levels were measured before, during and after comptetion of the trieI. In subjects inib ially consuming less than C.F. 59 daily there was a significant decrease in intestina; transit times and in colD-rectal pressures, and significant increase in stool weights. In subjects consuming more than C.E 5g daily, favourable changes in all of these parameters were recorded but they only reached significant levels in increased stool weight. Blood lipid levels were not altered and in spite of the high intake of potatoes, there was no increase in body weight. Introduction Evidence is accumulating that many diseases characteristic of modern Western civilization may be attributed in part to a deficiency of fibre intake (Burkitt and T r o w e l l 1975). Both diverticular disease (Painter and Burkitt, f975), and ischaemic heart disease (Trewell, 1973) have been shown to be closely associated with law-fibre diets. The experience of clinicians in the West of Ireland suggests that both of these diseases were still uncommon here until after the t93945 war, Preceding this period there had
been a progressive reduction in potato consumption accompanied by an increasing demand for foods containing sugar and white flour, and this trend has continued down to recent times (Brown et al., 1970). In view of these observations and the fact that trials conducted to estimate the effect of fibre on intestinal behaviour, stool characteristics, and body lipids have been almost entirely limited to cereals (Painter et al., 1972; Heaton, 1973; Hinton et a/., 1969) it was decided to study the physiological effects of increasing potato intake. At present the average daily C.F. intake from all sources (total C.F. or T.C.F.) in Connecticut, U.S.A. has been assessed as about 3.5g (Dodlrlan et al., 1976). This is about one-sixth that of rural Africans who are minimally affected by modern Western diseases (Lubbe, 1971). In 1860 the starchy daily C,F. intake in England and Wares alone was estimated to have been about 2.6-3,79 with T.C.F. 4.f -5.2g. These figures declined in 1979 to starchy C.F 1.4g and T C F 4.1g (Trowell, 1976) It was therefore de~ided ~o estimate the effect of approximately doubling the T.CF. intake, but using starchy Iced which allegedly has more effect in human physiology than that derived from fruit and green vegetables. One kg of potato contains approximately C F 5g. Subjects and Methods Forty-eight apparently normal volunteers were evaluated before the trial.
*Present address : Dept. of Thoracic and CardJovascular Surgery, Arhus, Kommunehospital, 8000 Arhus C., Denmark 285
286
IRISH JOURNAL OF MEOICAL SCIENCE
One of US (J,F.) discussed in detail each volunteer's daily food intake. The appropriate amount of each C.F. containing food was then selected and weighed. From this, by using standard values obtained from the American Board of Food and NJ.ltrition, the daily TC.F. intake together with the amount derived from potato was calculated for each volunteer. Intestinal transit times, daily stoo] weights, colo-rectal pressure, total body weights and blood lipid levels were now measured. Each subject was then requested to consume approximately l k g of boiled or baked potatoes a day for a minimum of 10 weeks, At the end of this period all studies were repeated. No restrictions were placed on the volunteer's diet otherwise. He was free to eat what he chose apart from the requested amount of potato. Twenty three completed the trial. The main reasons for defaulting were difficulty in attaining the required potato imake, dislike of pressure recordings or dislike of stool collectiQn. All subjects were urban males aged 20-56 years from a variety of occupations including hospital staff, army personnel, students and business men. Five of the 23 were found to be consuming what by Western standards was a substantial amount of C.F., i.e. over 5g daily on average. The remaining 18 (78 per cenf) were consuming less than 5g CF. daily, with an avers.ge of 3.5g. This figure approximates closely to present British and Connecticut standards which are thought to be deficient in fibre. For the purpose of calcutating results, therefore, it was decided to constitute a Group I (5) of those consuming more than 5g C F, daily and a Group II (18) of those consuming less than 5g C.F. daily. The age range in each group was similar. Transit times were studied by the method of Hinton (Hinton e t a l . , 1969) using barium impregnated pellets of the same specific gravity as the bowel contents. Twenty-five peltets were ingested
and the time ~(aken for 80 per cent of these to be passed was recorded. In order to exclude the possibility that a substantial part of this change in transit times occurred in the stomach and smag b o w e l a separate study was undertaken in which mouth-to-caecum fransd time was measured in 10 subjects by means of an image infensifier following ingestion of barium peilets. This transit t~m8 was studied on normal diet and after two wesks on a high potato diet. The mean pre-diet mouth fo-caecum transit time was seven hours, whilst on the potato diet it was six hours. Any change in total transit time was therefore concluded to be effectively a change in colo-rectal transit time. Bowel pressures were measured in the rectum and sigmoid colon using open tipped catheters linked to Stathem transducers (PD 23} with a write-out on a Devices M 19 recorder Recordings obtained were analysed according to the method of Smith (Attisha and Smith, 1969). ReSults Increased potato consumption was associaled with large stools which tended to be soft, and. unformed, but not loose, and which were easily evacuated, Table I shows the average daily tota] C.F. intake before and during the trial, and also the CF. intake derived from potato. Table II shows that stool weights increased signilicantly in both groups, but particularly in Group Ih The number of stools weighing over 200 g per day is
Group I II
Period Before During Before During
Crude fibre grams/day Total 5,6 SD -1=0.628 73 SB= I 0.758 355 SB= • 66 SD-- +0.49
Potato 2.1 41 1.0 43
THE POTATO AS A SOURCE OF FIBRE rN THE DIET also significantly increased in both groups Transit time was not shortened significantfy in Group I but was in Group II. Table Ill shows that mean peak heights and waves greater than 50 cm H=O and motility index were all significantly reducec~ in Group II, but not in Group L
287
l~iscusslon mid Conclusions This trial has demonstrated that potatoes c a n alter intestinal behaviour, increasing stool weight, r e d u c i n g transit time and reduci~lg colo-rectal pressures. The most striking effect of the potato diet was seen in Group II (78 per cent of those c o m p l e t i n g trial). All three main
TABLE II Group
Stool weights
I
200gin
Transit
Beore
149 SD~45
0
46
During
249 SD• P
