Long term effects of guar gum on lipid metabolism after carotid endarterectomy
BMJ 1995; 310 doi: https://doi.org/10.1136/bmj.310.6972.95 (Published 14 January 1995) Cite this as: BMJ 1995;310:95
- Juha-Pekka Salenius, consultant vascular surgeona,
- Esko Harju, assistant professorb,
- Hannu Jokela, chief chemistc,
- Heikki Riekkinen, consultant vascular surgeona,
- Matti Silvasti, head of clinical unitd
- a Department of Surgery, University Hospital, 33520 Tampere, Finland
- b Tampere University, 33520 Tampere, Finland
- c Clinical Chemistry, University Hospital, 33520 Tampere, Finland
- d Orion-Farmos, PO Box 1780, 70701 Kuopio, Finland
- Correspondence to: Dr J-P Salenius, Division of Vascular Surgery, New England. Deaconess Hospital, 110 Francis Street, Boston, MA 02215, USA.
- Accepted 19 August 1994
Open studies in hypercholesterolaemia with guar gum, a dietary fibre obtained from Cyamopsis tetragonolobus, have shown 10% to 15% reductions in serum concentration of total cholesterol and 10% to 20% in serum concentration of low density lipoprotein cholesterol after short term treatment. The results from long term studies have been conflicting. To assess long term efficacy of guar gum we treated 40 patients with moderate hypercholesterolaemia for 24 months.
Patients, methods, and results
This randomised double blind, placebo controlled trial with two parallel groups was approved by the university's ethics committee, and subjects' consent was obtained.
Between August 1987 and November 1989, 40 consecutive patients without diabetes were operated on for a haemodynamically measurable carotid stenosis. Both groups comprised 16 men and four women, whose mean age was 63 years (range 49 to 81) and mean body weight 75.8 kg (55.0 to 97.0). There were no group differences in age, sex, or body weight. Serum lipid concentrations were equal, but triglyceride concentrations tended to be higher in the group allocated to treatment with guar gum (see table). After operation aspirin (250 mg/day) alone or with dipyridamole (225 mg/day) was used. None had drug treatment for hypercholesterolaemia. Thirty seven patients completed the trial. Follow up in both groups was from 24 to 29 months (mean 24.6 months).
Postoperatively patients received 5 g granulated guar gum (Guarem, Orion-Farmos, Espoo, Finland) or placebo three times a day, but otherwise they maintained their usual dietary habits and physical activity. All received dietary advice before treatment. Adverse events and compliance with treatment were monitored at 1, 3, 6, 12, and 24 months. Venous blood (20 ml) was drawn after an overnight fast to measure lipid concentrations before operation and at 12 and 24 months of follow up.
Multiple analysis of variance was performed for each serum lipid and lipoprotein concentration. Measurements at 12 and 24 months were used asdependent variables and pretreatment values as covariates. Differences between treatments were tested with Wilk's lambda. Further comparisons at 12 and 24 months were made by a t test, and 95% confidence intervals were calculated for differences between treatments adjusted to values before treatment.
Significant differences between treatments were found in concentrations of both total and low density lipoprotein cholesterol. The adjusted differences were 0.69 mmol/l (P=0.014) at 12 months and 1.07 mmol/l (P=0.0003) at 24 months for total cholesterol concentration and 0.75 mmol/l (P=0.0048) and 1.10 mmol/l (P=0.00005) for concentration of low density lipoprotein cholesterol. The concentrations of other lipids and lipoproteins remained virtually unchanged in both groups (table).
There was no reduction in body weight in either group; the final mean weight was 74.9 kg (range 52.0–95.0). Two patients in the guar group withdrew, the first because of flatulence and diarrhoea, the other because of inability to follow the protocol. One patient in the placebo group withdrew because of diarrhoea.
Mean (SE) serum concentrations of lipids and lipoproteins before treatment and after 12 and 24 months of treatment with guar gum or placebo
Comment
Previous trials of guar gum have been criticised for being short, uncontrolled, and small.1 Among the numerous long term trials known to us our study of 24 months was the first to be double blind and placebo controlled.
Secondary prevention of atherosclerosis is indicated after vascular procedures. The rate of carotid restenosis is 10–20%2 and is strongly associated with hypercholesterolaemia.3 Lipid concentrations after diets are often moderate but unacceptable in patients with vascular disease, and some adjunct is clearly desirable.
Our results confirm previous findings on the effects of guar gum on lipid metabolism during long term treatment.4 Response to guar seems not to depend on the initial total serum cholesterol concentration; the reduction in serum total cholesterol concentration was 17% and, in low density lipoprotein cholesterol was 26%. We observed no attenuation of the lipid lowering effect such as described elsewhere.5
Previous doses of guar gum have varied from 15 g to 30 g. Here 15 g a day proved effective. In keeping with earlier reports, body weight was unaltered.
The adverse effects of guar gum may vary according to dose, formulation, and method of administration. Toleration of granulated guar gum with meals was good; only one patient interrupted treatment because of gastrointestinal complaints. This contrasts with results from earlier studies.
We conclude that 15 g guar gum daily considerably reduces serum concentrations of total and low density lipoprotein cholesterol without attenuation over two years of treatment.
We thank Mr P Korhonen for statistical help and Orion-Farmos for sponsoring this study.