Scientific Name(s): Cyamopsis psoralioides DC., Cyamopsis tetragonolobus (L.) Taub.
Common Name(s): Guar, Guar flour, Indian cluster bean, Jaguar gum
The guar plant is a small nitrogen-fixing annual that bears pods, each containing a number of seeds. Native to tropical Asia, the plant grows throughout India and Pakistan and has been cultivated in the southern US since the beginning of the 20th century.1 Another name for this species is C. psoralioides DC.
Guar gum is a dietary fiber obtained from the endosperm of the bean, which can account for more than 40% of the seed weight. It is separated and ground to form commercial guar gum. Guar beans may be eaten as green beans, used as fertilizer, or fed to cattle.2
Guar gum is reported to contain 75% soluble fiber, 7.6% insoluble fiber, 2% crude protein, 0.78% fat, 0.54% ash, and 9.6% moisture.2 Synonyms are Cyamopsis psoralioides DC.
Guar gum has been used for centuries as a thickening agent for foods and medicines. The largest market for guar gum is the food industry, where guar gum is known as food additive code E412.2 Guar gum continues to find extensive use for these applications as well as in the paper, textile, and oil drilling industries.
Guar is a galactomannan polysaccharide that forms a viscous gel when placed in contact with water. It forms solutions that range from slightly acidic to neutral pH. Even at low concentrations (1% to 2%), guar gum forms gels in water. The viscosity of these gels is generally unaffected by the pH of the solution.
Food grade guar gum contains approximately 80% guaran (a galactomannan composed of D-mannose and D-galactose units) with an average molecular weight of 220 kDa. The overall ratio of mannose to galactose is approximately 2:1.3 However, guar gum is not a uniform product and its viscosity may vary in proportion to the degree of galactomannan cross-linking.
Because of this physical composition, guar gum–based matrix tablets are currently being evaluated as a method of administering sustained-release drugs, including diltiazem,4, 5 and for colonic drug delivery of corticosteroids to patients with inflammatory bowel disease.6
Uses and Pharmacology
In a 60-day study of Wistar rats, diets containing 10% and 20% weight/weight guar gum resulted in lower serum cholesterol, triacylglycerol, and LDL cholesterol levels as well as higher high-density lipoprotein (HDL) cholesterol levels.3 Rats fed guar gum had significantly lower lymph flow compared with rats fed cellulose (3.88 ± 1.31 and 11.9 ± 1.1 mL, respectively; P < 0.005). Additionally, rats fed guar gum had significantly reduced transport of cholesterol (4.6 ± 1.77 and 18.1 ± 1.1 mg, respectively; P < 0.0005), triacylglycerols (66.8 ± 35.3 and 297 ± 27 mg, respectively; P < 0.05), and phospholipids (13.7 ± 6.7 and 36 ± 2.5 mg, respectively; P < 0.05).7 Triglycerides in the plasma and liver were lower in rats that were fed fructose and given supplemental guar gum hydrolysate.8
Guar gum has been shown to have positive effects on cholesterol at doses ranging from 12 to 15 g/day. Most short-term studies (less than 1 year) in patients with mild to moderate hypercholesterolemia have demonstrated a decrease in serum total cholesterol levels by approximately 6.5% to 15% and LDL cholesterol by between 10.5% and 25% without any effect on triglycerides or HDL cholesterol levels.9, 10, 11, 12, 13 A long-term study in 40 patients illustrated that the effects of guar gum on total cholesterol and LDL cholesterol were sustained with continued use over a period of 24 months.14 A comprehensive review of the lipid-lowering effects of guar gum described a general hypothesis for the mechanism of this action: Guar reduces cholesterol absorption and increases bile excretion, leading to increased hepatic turnover of cholesterol. It has been suggested that the effects of guar on LDL cholesterol metabolism are similar to those of bile-sequestering agents.15
Guar gum also has been used as an adjunct to more conventional lipid-lowering therapy. Coadministration with lovastatin resulted in a larger decrease in total cholesterol levels (44%) compared with lovastatin alone (34%) after 18 weeks of treatment.16 Placebo-controlled trials have used a number of methods in an attempt to mask guar gum's unpleasant flavor, including uncoated granules,17 powders, crispbreads, and other flavored formulas.18
In a study of 141 patients with metabolic syndrome, guar gum 3.5 g given 3 times daily was found to improve LDL cholesterol and apolipoprotein B following 6 months of treatment.19
The ability of guar to alter viscosity20 and thus affect GI transit results in delayed absorption of glucose and may contribute to its hypoglycemic activity.
In a study of Wistar rats, diets containing 10% and 20% weight/weight guar gum were associated with lower glucose levels after 30 days of feeding compared with other diets assessed. However, after 60 days of feeding, blood glucose levels were relatively higher in all diet groups, with no effect noted with guar gum.3 In another study of healthy rats, intragastric administration of guar gum and glucose was associated with a smaller peak increment in plasma glucose, insulin, and glucagon-like peptide 1 concentration.21 Guar gum hydrolysate was found to improve glucose intolerance in rats given fructose-based diets on day 28 of administration.8
In diabetic rats fed a 5% guar gum diet for 8 weeks, a significant improvement in hemoglobin A1c (HbA1c) was noted (12.4%) compared with that of rats receiving a basal diet (14.4%, P < 0.05). Additionally, the weight of the kidney was less in the group receiving guar gum compared with the group receiving a basal diet (2.76 vs 3.51 g, respectively; P < 0.05). Urinary albumin excretion was highest in the basal diet group and intermediate in the guar gum diet group.22
In another study, rats with streptozotocin-induced diabetes fed a diet containing 20% guar gum experienced a greater reduction in glucose levels after 28 days of administration compared with those receiving glibenclamide 2 mg/kg.23
Guar reduces postprandial glucose and insulin levels in healthy subjects20 and in patients with type 2 diabetes mellitus.24, 25, 26, 27, 28, 29 No reduction in plasma C-peptide levels was observed, suggesting that guar gum attenuates insulin concentration in peripheral venous blood by increasing the hepatic extraction of insulin.29 These effects on glucose and insulin seem to be most pronounced when large amounts of guar gum are added to the diet, and when the fiber is administered with the glucose or food.30 However, when dietary fats and proteins are not adequately controlled in the diabetic diet, the addition of guar was shown to have little effect on postprandial glucose or C-peptide responses.31
In a study of 141 overweight, hypertensive patients, guar gum 3.5 g 3 times daily was associated with a significant reduction in fasting plasma glucose of 10 mg/dL after 4 months (P = 0.009) and 12 mg/dL after 6 months (P = 0.009). Additionally, HbA1c significantly decreased by 0.7% after 6 months of therapy (P < 0.001).32
The effects of 48 weeks of guar gum were assessed in a single-blind, placebo-controlled study of 15 patients with type 2 diabetes mellitus. Specifically, all patients received placebo for 8 weeks (placebo period 1) followed by 48 weeks of guar gum 15 g/day or placebo divided into 3 doses and then another 8-week placebo period (placebo period 2). HbA1c levels were lower during guar gum treatment compared with placebo period 1, with no change during placebo period 2. Fructosamine levels were lower after treatment with guar gum compared with the end of placebo period 1; however, upon stopping guar gum, the fructosamine level began to increase as noted in placebo period 2. Additionally, C-peptide response increased after 48 weeks of treatment with guar gum. However, even after stopping guar gum for 8 weeks, C-peptide levels were higher at the end of placebo period 2 compared with placebo period 1 and after 16 weeks of guar gum.33
Preparations containing guar gum have been used extensively to promote normal GI motility and to maintain fecal bulk.34 Guar preparations may delay gastric emptying time or GI transit, but these effects seem to be related to the type of meal and diet.
A 5% partially hydrolyzed guar gum diet in mice attenuated dextran sulfate sodium–induced colitis. After 2 weeks of prefeeding with guar gum, a reversal in shortening of the colon occurred. Additionally, disease activity index scores (ie, measuring weight loss, stool consistency, blood in stool) were lower in mice receiving guar gum compared with the controls.35
Oral rehydration solution, supplemented with guar gum, may reduce the duration of diarrhea in young children.36 Also, the addition of enzymatically modified guar gum to enteral formulas has been shown to increase GI transit time, increase fecal nitrogen excretion,37 and reduce diarrhea38 without any effects on normal absorption of glucose, amino acids, or fat, or any adverse effects on hematological, hepatic, or renal function.39 In a study of children with alternating diarrhea and constipation, Optifibre (partially hydrolyzed guar gum) improved these symptoms.40 Daily administration of partially hydrolyzed guar gum (3 g/day for patients 4 to 6 year of age, 4 g/day for patients 6 to 12 years of age, and 5 g/day for patients 12 to 16 years of age) for 4 weeks was as effective as lactulose at improving bowel movement frequency per week, stool consistency, and percentage of participants with abdominal pain and stool withholding.41
In a randomized, double-blind, placebo-controlled study, 60 women 18 to 65 years of age experiencing less than 3 bowel movements per week were randomized to receive 3 weeks of supplementation with 5 g/day of inulin and partially hydrolyzed guar gum given 3 times daily or placebo. An increase in bowel movement frequency and patient satisfaction occurred in both groups and was not statistically significant. Treatment with inulin and guar gum was associated with a decrease in the total Clostridium species (5.23 ± 0.67 cells/mcL at baseline compared with 4.76 ± 0.92 cells/mcL after treatment, P = 0.046), whereas women treated with placebo experienced an increase in total Clostridium sp. (5.14 ± 0.92 cells/mcL at baseline compared with 5.50 ± 0.91 cells/mcL after treatment, P = 0.047). The findings were statistically significant when comparing inulin/guar gum with placebo (P = 0.045).42
Seventy-seven patients with small intestinal bacterial overgrowth were randomized to receive 1,200 mg/day of rifaximin or 1,200 mg/day of rifaximin plus 5 g/day of partially hydrolyzed guar gum for 10 days. The eradication rate of small intestinal bacterial overgrowth was 62% in the group given rifaximin alone compared with 87% in the per-protocol group given rifaximin plus guar gum (P = 0.017) and 85% in the intention-to-treat group given rifaximin plus guar gum (P = 0.036). Clinical improvement was noted in 87% of patients receiving rifaximin alone compared with 91% in those receiving rifaximin plus guar gum (P = 0.677).43
A prospective, open-label study evaluated the effect of guar gum on colonic transit time (CTT) in adults (n = 39) with chronic constipation; bisacodyl or glycerin suppositories were allowed for rescue therapy during the study period. Daily partially hydrolyzed guar gum (5 mg) for 4 weeks significantly improved CTT, straining, and weeks with pain, specifically in patients with baseline slow transit time (P = 0.016, P < 0.001, and P = 0.027, respectively). The number of complete spontaneous bowel movements, spontaneous bowel movements, weeks with bloating, number of days/week taking laxatives, and stool form were significantly improved in patients with either slow or normal baseline transit times. No serious adverse events were reported.63
At 12 months after standard therapy with topical nitroglycerin 0.4% ointment for chronic anal fissure, patients who received oral supplementation of partially hydrolyzed guar gum (PHGG) 5 g/day for 10 months (7 cycles of 4 weeks spaced by 2-week intervals) achieved higher success rates (58.5% vs 38.3%; P = 0.019) and lower recurrence (14.5% vs 30.2%; P = 0.0047) than those without PHGG maintenance therapy.64
Research reveals no animal data regarding the use of guar gum for weight loss.
The results of 1 small study suggested that guar gum may have a more profound effect on satiety when added to a meal rich in fat than when added to a low-fat meal.45 A meta-analysis presented the combined results of 20 randomized controlled trials in which guar gum (average daily dose, 9 to 30 g) was compared with placebo.46 It was shown conclusively that guar gum is not effective in reducing body weight. Additionally, a number of studies using a partially hydrolyzed form of guar gum, which has no viscosity or bulking effect, have found no effect on appetite47 or weight maintenance.48 Although evidence for the effectiveness of fiber products as appetite suppressants is lacking, they remain popular ingredients in over-the-counter weight loss preparations.
In a study of 141 patients with metabolic syndrome, guar gum 3.5 g given 3 times daily was found to significantly decrease waist circumference after 4 months of treatment (−4.6 cm, P = 0.011). Waist circumference was decreased even further after 6 months of treatment (−5.2, P < 0.004).19
Guar gum has been reported to have varied effects on blood pressure.
Research reveals no animal data regarding the use of guar gum for blood pressure levels.
One small study of 10 elderly subjects showed a reduction in postprandial hypotension (PPH) (defined as a decrease in systolic blood pressure greater than 20 mm Hg occurring within 2 hours of the end of a meal).49 These data were corroborated in a double-blind, randomized, placebo-controlled, crossover trial in 22 older women in South Korean community senior centers in which significant differences in postprandial systolic blood pressure were noted between the guar gum (9 g pre-meal intervention) and control groups with the greatest difference (18.2 mm Hg; P = 0.004) observed at 45 minutes after eating. Additionally, the incidence of PPH was 18.2% vs 72.7% in the guar gum and control groups, respectively (P < 0.001). No significant changes were noted in postprandial diastolic blood pressure during the 120-minute follow up.65 Conversely, guar supplementation for 2 weeks was shown to reduce blood pressure by 9% in moderately overweight men.50 However, in a study of 141 hypertensive overweight patients, guar gum reduced systolic blood pressure after 2 months of supplementation (3.5 g 3 times daily); however, there was no difference after 4 and 6 months of supplementation.32 In another study of 141 patients with metabolic syndrome, guar gum 3.5 grams 3 times daily was associated with an improvement in systolic blood pressure (−5.3 mm Hg, P < 0.001) after 4 months of treatment. However, this effect was not assessed in further study visits, and no effect on diastolic blood pressure was noted.19
Intrahepatic cholestasis and pruritus in pregnancy
Research reveals no animal data regarding the use of guar gum for intrahepatic cholestasis and pruritus in pregnancy.
In 2 double-blind studies, guar gum diminished or prevented worsening of pruritus in 96 pregnant women with intrahepatic cholestasis. This outcome is related to bile acid concentration, which remained unchanged in guar gum–treated patients but increased in placebo recipients.51, 52 The authors suggest that guar gum is a safe alternative and possible treatment option in these patients.
Guar gum has been administered in amounts from 7.5 to 21 g daily in clinical trials for weight loss.53 For constipation in children, 1 study used partially hydrolyzed guar gum 3 g/day for patients 4 to 6 years of age, 4 g/day for patients 6 to 12 years of age, and 5 g/day for 12 to 16 years of age.41 Guar gum 8 to 36 g/day and 100 to 150 g/day of dried beans or legumes have been suggested to lower LDL cholesterol by 5% to 10%.2
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Guar gum is not teratogenic and does not affect reproduction in rats.54
Guar gum reduces the absorption of metformin, which may decrease the antihyperglycemic effect.53 The effect of ingestion of 10 g of guar gum on a single 1,700 mg dose of metformin was studied in 6 healthy subjects.53 Guar gum decreased metformin serum levels between 1.5 and 5 hours after administration. The metformin area under the curve was decreased 39% and the absorption rate decreased over the first 6 hours following coadministration of guar gum.
In the colon, guar gum is fermented to short-chain fatty acids. Both guar and its resultant by-products do not appear to be absorbed by the gut. The most common adverse effects are GI-related, including abdominal pain, cramps, diarrhea, and flatulence.55 Approximately 50% of people taking guar experience flatulence, which usually occurs early in treatment and resolves with continued use. A dose of approximately 3 g 3 times daily, not to exceed 15 g/day, can minimize GI effects.2, 56
Guar gum may affect the absorption of coadministered drugs. Slowed absorption of digoxin, acetaminophen, and bumetanide and decreased absorption of metformin, penicillin V, and some formulations of glyburide have been reported.57 Bezafibrate, glipizide, and glyburide58 are generally unaffected by coadministration.9
Guar gum in a weight-loss product was implicated as causing esophageal obstruction in a patient who exceeded the recommended dosage.59 In a review, 18 cases of esophageal obstruction, 7 cases of small bowel obstruction, and possibly 1 death were associated with the use of Cal-Ban 3000, a guar gum–containing diet pill.60 The water-retaining capacity of the gum can cause it to swell 10- to 20-fold and may lead to luminal obstruction, particularly when an anatomic predisposition exists. Guar should be taken with large amounts of liquid.
Occupational asthma has been observed among people working with guar gum.61, 62 One case report suggests a possible anaphylactic reaction to a meal substitute containing guar gum in which the patient tested positive in a skin test.62
There is little or no information regarding toxicity with the use of guar gum.
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This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.
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