- Email: [email protected]
"STARCH BLOCKERS" ARE INEFFECTIVE IN MAN
60 PROGRESSION TO TOTAL OCCLUSION IN CASES SELECTED FOR PTA
usually present in amounts far above those required for digestion of the luminal contents. The claim that these tablets prevent starch absorption can be tested with a test-meal of starch labelled with Bc.2 Normally the carbon dioxide in expired air is maximally labelled with BC about 3 h after the meal, and about 30% of the ingested 13C is oxidised to inhibit the CO2 within 6 h of the meal. If starch-blockers digestion of starch no labelling of expired CO2 withC should be observed. The subjects were five obese, non-diabetic, euthyroid women, 35± 11 years old, I -60±0 -04 m tall, weighing 88 -2±8 -5kg. They were tested on three
totall
*
Figures in parentheses refer to cases where PTA was no longer feasible so that surgery was
needed
The results are summarised in the table. In 20 out of 109 patients with initial femoral artery stenoses total arterial occlusion had developed by the time of the second angiogram. Thus almost 1 in 5 patients with angiographically confirmed stenosis in the femoropopliteal arteries progressed to total arterial obstruction within, on average, 6 weeks. Kuthan et a1. found, in an angiographic follow-up of 25 months, femoral artery stenosis progressing to total obstruction in 53% of cases. Bollinger et a1. demonstrated, by non-invasive flow measurements, total arterial obstruction in 27% of the patients within 5 months. Progression seems most serious in the early weeks. On the other hand, progression to total occlusion of iliac artery stenoses happened only once in 53 cases in our series. The initial iliac artery stenoses may have been less severe than the femoral artery narrowing or flow conditions prevailing in the iliac arteries may have been different. The possibility that angiography per se might accelerate the obstructive process5seems unlikely. Our angiograms were done by retrograde needle puncture of the artery without thrombus-forming catheters. We used as contrast medium of low osmolality that produces little endothelial irritation6 or flow disturbance. If anything, these precautions would have caused less damage than the contrast media used previously, but our progression rate was higher than van Andel’s.5 Even though an iatrogenic progression cannot be ruled out, the fact that femoral occlusion developed in 18% of stenoses remains, and has important practical implications. If femoro-popliteal stenosis suitable for PTA is only a transient state in the course of arterial occlusive disease and if total occlusion precludes PTA (as in most of our 21 patients), PTA, once planned, should not be delayed. ’
Cardiovascular Research Unit, Hammersmith Hospital, London W12 0HS
University Clinic of Medicine,
occasions after an overnight fast of 14 h with a meal containing 75 g cornflour in the form of a blancmange flavoured with lemon. 10 min before the meal, m random sequence, a tablet of either ’Calorex’ (Britannia Health Products, Reigate, Surrey) or ’Starchex’ (Doeskin Ltd, London EC1) or an antacid placebo (’Gelusil’; Warner, Pontypool, Gwent) was ingested. Some subjects were unable to consume the complete test meal within 30 min, but all ate the same amount for each test. For 30 min before the meal and 6 h after the meal, metabolic rate and rate of production were measured.4Breath samples were taken for analysis of 3C on three occasions before the meal and half-hourly after the meal for 6 hours. In two women blood was taken before and hourly for 3 h after the meal for measurement of blood glucose and plasma insulin. The study was approved by the Northwick Park Hospital ethical committee.
CO2025
The weight of starch in the test meals ranged from 44 to 64 g. One unable to ingest the test meal within 30 min after taking the placebo tablet, so there are no data for this test, and two had placebo studies in duplicate. The mean ±SD percentage oxidation within 6 h of the test meal was 27 - 4:t3 . 9% after the placebo tablet, which is not significantly different from that after calorex (25 -· 7±24%) or after starchex (27 -7±3 -5%). Nor was there a significant difference in the rates of oxidation (figure). Thus neither starch-blocker tablet delayed either the digestion and further metabolism of the starch to any woman was
2. Lacroix
M, Mosora F, Pontus M, Lefebvre P, Luyckx A, Lopez-Habib G Glucose Use for metabolic studies in man. Science 1973;
naturally labelled with carbon-13:
181: 445-46. 3 Lefebvre PJ. Naturally labelled 13C-glucose: a new tool to measure oxidation rates of exogenous glucose. Diabetes 1979; 28: 63-65 4. Garrow JS, Hawes SF. The role of aminoacid oxidation in causing "specific dynamic action" in man. Br J Nutr 1972; 27: 211-19. 5. Halliday D, Rennie MJ. The use of stable isotopes for diagnosis and clinical research. Clin Sci 1982; 63: 485-96.
A. GALLINO
Bern, Switzerland
F. MAHLER
Institute for Diagnostic Radiology, Inselspital Bern
P. PROBST
"STARCH BLOCKERS" ARE INEFFECTIVE IN MAN
SIR,-The pancreatic starch-splitting a-amylase can be inactivated in vitro by many substances, including a protein extractable from the red kidney bean (Phaseolus vulgaris). A preparation of this protein is on sale to the public as a "starch blocker", and it is estimated that more than 10 million starchblocker tablets are consumed weekly in the United States.i However, there is no direct evidence that the preparation does inhibit starch digestion and absorption in man. It would be surprising for this protein to survive destruction in the stomach. Furthermore it cannot be assumed that inhibition of pancreatic amylase would affect starch digestion, since digestive enzymes are 3. Kuthan 4. 5. 6. 7
1
F, Burkhalter A, Baitsch R, Ludin H, Widmer LK. Development of occlusive arterial disease in lower limbs. Arch Surg 1971; 103: 545-47. Bollinger A, Simon HJ, Mahler F The natural course of peripheral arteriosclerosis obliterans evaluated by flow measurements. Angiology 1969; 20: 414-21 van Andel GJ. Arterial occlusion following angiography. Br J Radiol 1980; 53: 747-753. Almén T, Aspelin P Cardiovascular effects of ionic monomeric, ionic dimeric and nonionic contrast media. Invest Radiol 1975, 10: 557-63. Stäubli M, Braunschweig J, Tillmann U. Changes in the rheological properties of blood as induced by sodium/meglumine ioxaglate compared with sodium/meglumine diatrizoate and metrizamide. Acta Radiol Diagnos 1982; 23: 71-78. Anon. Much interest in new "starch blockers" Pharm J1982; 229: 124
Average percentage periods by five obese placebo (0).
of
carbohydrate meal oxidised in 30 min given calorex (0), starchex (A), or
women
61 measurable extent. This conclusion is supported by the glucose and insulin responses in two subjects 1 h after the meal the increases both in blood glucose and in plasma insulin were similar after all three tablets. Our results are irreconcilable with the claim that one 500 mg tablet of starch-blocker prevents the absorption of 100 g of starch ingested 10 min later.’ The rate of carbohydrate oxidation we observed matches that observed by usand others7 for glucose loads: this eliminates any possibility that our labelled starch preparation was resistant to digestion or that the placebo tablet unexpectedly had a starch-blocker action. People who buy starch blocker preparations in the belief that they can then eat starch but not absorb it are misguided. We thank Mrs S. Sunkin and Mrs E. Austin for
Nutrition Research Group, Clinical Research Centre, Harrow, Middlesex HA1 3UJ
preparing the test meals. J. S. GARROW P. F. SCOTT SUSAN HEELS K. S. NAIR D. HALLIDAY
NMR IMAGING IN PREGNANCY
SIR,-We have used nuclear magnetic resonance (NMR) to examine 6 patients in the first trimester of pregnancy and have compared the findings with the results of ultrasound. The high level of contrast seen in images produced by NMR is dependent upon the relation of water to body proteins and fluids, reflected in the proton spin-lattice relaxation times (Tl) of different tissues.The technique is non-invasive and appears to have no short or medium term
side-effects.9
6 patients, aged between 16 and 21 years, who had been admitted for termination of pregnancy by prostaglandin infusion at between 12 and 20 weeks gave their informed consent to pelvic examination by ultrasound and NMR imaging. Ultrasound measurement was made of the fetal biparietal diameter, crown-rump length, and trunk area and circumference, and the gestational age was estimated. The size of the placenta was also noted. NMR images were made with the Aberdeen imager. 10, 11Results were displayed as proton density, Tl, and, a combination of these, the D image which provides a good anatomical display, especially when long T fluids are present which obscure underlying structures. Biparietal diameter was measured from the proton density images (table), and measurements of the uterus, placenta, amniotic fluid, and fetus were made from the T image. The D image was used to localise these structures when they were obscured by amniotic fluid, which appears as white in the
Fig. 1-T1 (upper) and D (lower) images (16-18 wk fetus). Transverse section showing fetal head lymg to left of uterine cavity. Uterus and posterior placenta can be seen clearly. The long T of the ammotic fluid appears as white with areas of black due to "over-range" artifact, and obscures the fetus.
placenta because of the large difference in proton density between these tissues and amniotic fluid (pelvic bones appear black with grey marrow). The thickness of the uterine wall and placenta could be measured best from the Timages. However, the D image proved to be the best for demonstrating all structures. At 10 weeks the products of conception were demonstrable by NMR imaging and placental localisation and biparietal measurements were comparable with results obtained by ultrasound. At 16-18 weeks the fetal head and body are easily seen (fig. 1), and by 20 weeks (fig. 2) the entire fetus is clearly demonstrated. At present only axial sections are possible with NMR imaging and we were unable to
T images (fig. 1). Gestational age and placental site were determined by ultrasound. The NMR proton density images show the uterine cavity, fetus, and 6. Nair KS, Halliday D, Garrow JS 13CO2 production from glucose in obese subjects with glucose intolerance and normal lean controls. Clin Sci 1982; 63: 67P. 7. Felber J-P, Meyer HU, Curchod B et al. Glucose storage and oxidation in different
degrees of human obesity measured by continuous indirect calorimetry. Diabetologia 1981; 20: 39-44. 8. Mallard JR, Hulchison JMS, Edelstein WA, Ling CR, Foster MA, Johnson G In vivo N.M R imaging in medicine the Aberdeen approach both physical and biological. Phil Trans Roy Soc Lond B 1980; 289: 519-33. 9. Reid A, Smith FW, Hutchison JMS. Nuclear magnetic resonance imaging and its safety implications. follow-up of 181 patients. Br J Radiol 1982; 55: 784-86. 10. Hutchison JMS, Edelstein WA, Johnson G. A whole-body N.M.R. imaging machine. J Phys E Sci Instrumen 1980, 13: 947-55. 1 . Edelstein WA, Hutchison JMS, Johnson G, Redpath TW. Spin-warp N.M R imaging and applications to whole-body imaging. Phys Med Biol 1980; 25: 751-65 COMPARATIVE RESULTS WITH NMR AND ULTRASOUND
Fig. 2-Proton density (upper) and D image (lower) (20 wk fetus). Fetal head hes wall of uterus.
posteriorly with body
to
the
right. Placenta lies
on
anterior
usually present in amounts far above those required for digestion of the luminal contents. The claim that these tablets prevent starch absorption can be tested with a test-meal of starch labelled with Bc.2 Normally the carbon dioxide in expired air is maximally labelled with BC about 3 h after the meal, and about 30% of the ingested 13C is oxidised to inhibit the CO2 within 6 h of the meal. If starch-blockers digestion of starch no labelling of expired CO2 withC should be observed. The subjects were five obese, non-diabetic, euthyroid women, 35± 11 years old, I -60±0 -04 m tall, weighing 88 -2±8 -5kg. They were tested on three
totall
*
Figures in parentheses refer to cases where PTA was no longer feasible so that surgery was
needed
The results are summarised in the table. In 20 out of 109 patients with initial femoral artery stenoses total arterial occlusion had developed by the time of the second angiogram. Thus almost 1 in 5 patients with angiographically confirmed stenosis in the femoropopliteal arteries progressed to total arterial obstruction within, on average, 6 weeks. Kuthan et a1. found, in an angiographic follow-up of 25 months, femoral artery stenosis progressing to total obstruction in 53% of cases. Bollinger et a1. demonstrated, by non-invasive flow measurements, total arterial obstruction in 27% of the patients within 5 months. Progression seems most serious in the early weeks. On the other hand, progression to total occlusion of iliac artery stenoses happened only once in 53 cases in our series. The initial iliac artery stenoses may have been less severe than the femoral artery narrowing or flow conditions prevailing in the iliac arteries may have been different. The possibility that angiography per se might accelerate the obstructive process5seems unlikely. Our angiograms were done by retrograde needle puncture of the artery without thrombus-forming catheters. We used as contrast medium of low osmolality that produces little endothelial irritation6 or flow disturbance. If anything, these precautions would have caused less damage than the contrast media used previously, but our progression rate was higher than van Andel’s.5 Even though an iatrogenic progression cannot be ruled out, the fact that femoral occlusion developed in 18% of stenoses remains, and has important practical implications. If femoro-popliteal stenosis suitable for PTA is only a transient state in the course of arterial occlusive disease and if total occlusion precludes PTA (as in most of our 21 patients), PTA, once planned, should not be delayed. ’
Cardiovascular Research Unit, Hammersmith Hospital, London W12 0HS
University Clinic of Medicine,
occasions after an overnight fast of 14 h with a meal containing 75 g cornflour in the form of a blancmange flavoured with lemon. 10 min before the meal, m random sequence, a tablet of either ’Calorex’ (Britannia Health Products, Reigate, Surrey) or ’Starchex’ (Doeskin Ltd, London EC1) or an antacid placebo (’Gelusil’; Warner, Pontypool, Gwent) was ingested. Some subjects were unable to consume the complete test meal within 30 min, but all ate the same amount for each test. For 30 min before the meal and 6 h after the meal, metabolic rate and rate of production were measured.4Breath samples were taken for analysis of 3C on three occasions before the meal and half-hourly after the meal for 6 hours. In two women blood was taken before and hourly for 3 h after the meal for measurement of blood glucose and plasma insulin. The study was approved by the Northwick Park Hospital ethical committee.
CO2025
The weight of starch in the test meals ranged from 44 to 64 g. One unable to ingest the test meal within 30 min after taking the placebo tablet, so there are no data for this test, and two had placebo studies in duplicate. The mean ±SD percentage oxidation within 6 h of the test meal was 27 - 4:t3 . 9% after the placebo tablet, which is not significantly different from that after calorex (25 -· 7±24%) or after starchex (27 -7±3 -5%). Nor was there a significant difference in the rates of oxidation (figure). Thus neither starch-blocker tablet delayed either the digestion and further metabolism of the starch to any woman was
2. Lacroix
M, Mosora F, Pontus M, Lefebvre P, Luyckx A, Lopez-Habib G Glucose Use for metabolic studies in man. Science 1973;
naturally labelled with carbon-13:
181: 445-46. 3 Lefebvre PJ. Naturally labelled 13C-glucose: a new tool to measure oxidation rates of exogenous glucose. Diabetes 1979; 28: 63-65 4. Garrow JS, Hawes SF. The role of aminoacid oxidation in causing "specific dynamic action" in man. Br J Nutr 1972; 27: 211-19. 5. Halliday D, Rennie MJ. The use of stable isotopes for diagnosis and clinical research. Clin Sci 1982; 63: 485-96.
A. GALLINO
Bern, Switzerland
F. MAHLER
Institute for Diagnostic Radiology, Inselspital Bern
P. PROBST
"STARCH BLOCKERS" ARE INEFFECTIVE IN MAN
SIR,-The pancreatic starch-splitting a-amylase can be inactivated in vitro by many substances, including a protein extractable from the red kidney bean (Phaseolus vulgaris). A preparation of this protein is on sale to the public as a "starch blocker", and it is estimated that more than 10 million starchblocker tablets are consumed weekly in the United States.i However, there is no direct evidence that the preparation does inhibit starch digestion and absorption in man. It would be surprising for this protein to survive destruction in the stomach. Furthermore it cannot be assumed that inhibition of pancreatic amylase would affect starch digestion, since digestive enzymes are 3. Kuthan 4. 5. 6. 7
1
F, Burkhalter A, Baitsch R, Ludin H, Widmer LK. Development of occlusive arterial disease in lower limbs. Arch Surg 1971; 103: 545-47. Bollinger A, Simon HJ, Mahler F The natural course of peripheral arteriosclerosis obliterans evaluated by flow measurements. Angiology 1969; 20: 414-21 van Andel GJ. Arterial occlusion following angiography. Br J Radiol 1980; 53: 747-753. Almén T, Aspelin P Cardiovascular effects of ionic monomeric, ionic dimeric and nonionic contrast media. Invest Radiol 1975, 10: 557-63. Stäubli M, Braunschweig J, Tillmann U. Changes in the rheological properties of blood as induced by sodium/meglumine ioxaglate compared with sodium/meglumine diatrizoate and metrizamide. Acta Radiol Diagnos 1982; 23: 71-78. Anon. Much interest in new "starch blockers" Pharm J1982; 229: 124
Average percentage periods by five obese placebo (0).
of
carbohydrate meal oxidised in 30 min given calorex (0), starchex (A), or
women
61 measurable extent. This conclusion is supported by the glucose and insulin responses in two subjects 1 h after the meal the increases both in blood glucose and in plasma insulin were similar after all three tablets. Our results are irreconcilable with the claim that one 500 mg tablet of starch-blocker prevents the absorption of 100 g of starch ingested 10 min later.’ The rate of carbohydrate oxidation we observed matches that observed by usand others7 for glucose loads: this eliminates any possibility that our labelled starch preparation was resistant to digestion or that the placebo tablet unexpectedly had a starch-blocker action. People who buy starch blocker preparations in the belief that they can then eat starch but not absorb it are misguided. We thank Mrs S. Sunkin and Mrs E. Austin for
Nutrition Research Group, Clinical Research Centre, Harrow, Middlesex HA1 3UJ
preparing the test meals. J. S. GARROW P. F. SCOTT SUSAN HEELS K. S. NAIR D. HALLIDAY
NMR IMAGING IN PREGNANCY
SIR,-We have used nuclear magnetic resonance (NMR) to examine 6 patients in the first trimester of pregnancy and have compared the findings with the results of ultrasound. The high level of contrast seen in images produced by NMR is dependent upon the relation of water to body proteins and fluids, reflected in the proton spin-lattice relaxation times (Tl) of different tissues.The technique is non-invasive and appears to have no short or medium term
side-effects.9
6 patients, aged between 16 and 21 years, who had been admitted for termination of pregnancy by prostaglandin infusion at between 12 and 20 weeks gave their informed consent to pelvic examination by ultrasound and NMR imaging. Ultrasound measurement was made of the fetal biparietal diameter, crown-rump length, and trunk area and circumference, and the gestational age was estimated. The size of the placenta was also noted. NMR images were made with the Aberdeen imager. 10, 11Results were displayed as proton density, Tl, and, a combination of these, the D image which provides a good anatomical display, especially when long T fluids are present which obscure underlying structures. Biparietal diameter was measured from the proton density images (table), and measurements of the uterus, placenta, amniotic fluid, and fetus were made from the T image. The D image was used to localise these structures when they were obscured by amniotic fluid, which appears as white in the
Fig. 1-T1 (upper) and D (lower) images (16-18 wk fetus). Transverse section showing fetal head lymg to left of uterine cavity. Uterus and posterior placenta can be seen clearly. The long T of the ammotic fluid appears as white with areas of black due to "over-range" artifact, and obscures the fetus.
placenta because of the large difference in proton density between these tissues and amniotic fluid (pelvic bones appear black with grey marrow). The thickness of the uterine wall and placenta could be measured best from the Timages. However, the D image proved to be the best for demonstrating all structures. At 10 weeks the products of conception were demonstrable by NMR imaging and placental localisation and biparietal measurements were comparable with results obtained by ultrasound. At 16-18 weeks the fetal head and body are easily seen (fig. 1), and by 20 weeks (fig. 2) the entire fetus is clearly demonstrated. At present only axial sections are possible with NMR imaging and we were unable to
T images (fig. 1). Gestational age and placental site were determined by ultrasound. The NMR proton density images show the uterine cavity, fetus, and 6. Nair KS, Halliday D, Garrow JS 13CO2 production from glucose in obese subjects with glucose intolerance and normal lean controls. Clin Sci 1982; 63: 67P. 7. Felber J-P, Meyer HU, Curchod B et al. Glucose storage and oxidation in different
degrees of human obesity measured by continuous indirect calorimetry. Diabetologia 1981; 20: 39-44. 8. Mallard JR, Hulchison JMS, Edelstein WA, Ling CR, Foster MA, Johnson G In vivo N.M R imaging in medicine the Aberdeen approach both physical and biological. Phil Trans Roy Soc Lond B 1980; 289: 519-33. 9. Reid A, Smith FW, Hutchison JMS. Nuclear magnetic resonance imaging and its safety implications. follow-up of 181 patients. Br J Radiol 1982; 55: 784-86. 10. Hutchison JMS, Edelstein WA, Johnson G. A whole-body N.M.R. imaging machine. J Phys E Sci Instrumen 1980, 13: 947-55. 1 . Edelstein WA, Hutchison JMS, Johnson G, Redpath TW. Spin-warp N.M R imaging and applications to whole-body imaging. Phys Med Biol 1980; 25: 751-65 COMPARATIVE RESULTS WITH NMR AND ULTRASOUND
Fig. 2-Proton density (upper) and D image (lower) (20 wk fetus). Fetal head hes wall of uterus.
posteriorly with body
to
the
right. Placenta lies
on
anterior