PHYSIOLOGICAL FUNCTIONS OF KGM

3.7 PHYSIOLOGICAL FUNCTIONS OF KGM

Dietary fiber has recently received recognition for reducing the risk of developing diabetes and heart disease, because it has a therapeutic benefit in prediabetic meta- bolic conditions. KGM has been chosen as a dietary fiber because it represents a polysaccharide with one of the highest viscosities.

Vuksan et al. 46 studied the effect of KGM fiber on type 2 diabetic patients, as an adjunct to conventional treatment, on a cluster of coronary heart disease (CHD) risk factors: hyperglycemia, hyperlipidemia, and hypertension. The experimental observation showed that the application of KGM supplementation in a high-risk diabetic study group demonstrated simultaneous improvement in all three diet- modifiable risk factors, indicating a reduction in overall CHD risk. Furthermore, KGM-supplemented therapy may require lower drug dosages and improve overall cost-effectiveness and acceptability of treatment.

Konjac Glucomannan

Vuksan et al. 47 screened 278 free-living subjects between the ages of 45 and

65 years from the Canadian-Maltese Diabetes Study. A total of 11 (age, 55 ± 4 years; body mass index (BMI), 28 ± 1.5 kg/m 2 ) were recruited who satisfied the inclusion criteria: impaired glucose tolerance, reduced high-density lipoprotein (HDL) cholesterol, elevated serum triglycerides, and moderate hypertension. After an 8-week baseline, they were randomly assigned to take either KGM fiber- enriched test biscuits (0.5 g of glucomannan per 100 kcal of dietary intake, or 8 to 13 g/day) or wheat bran fiber (WB) control biscuits for two 3-week treatment periods separated by a 2-week washout. The diets were isoenergetic, metabolically controlled, and conformed to National Cholesterol Education Program Step 2 guidelines. Serum lipids, glycemic control, and blood pressure were the outcome measures. Decreases in serum cholesterol, apolipoprotein, and serum fructosamine were observed during KGM treatment compared with the WB control. Blood glucose, insulin, triglycerides, HDL cholesterol, and body weight remained unchanged. These indicated that a diet rich in high-viscosity KGM improves glycemic control and lipid profile, suggesting a therapeutic potential of KGM fiber in the treatment of the insulin resistance syndrome.

Vuksan and his collaborators 48 have selected two such promising and function- ally complementary therapies for further investigation as potential treatment alter- natives for type 2 diabetes: KGM and American ginseng (AG). They have generated

a mounting body of evidence to support the claim that rheologically selected, highly viscous KGM, and AG with a specific composition may be useful in improving

diabetes control, reducing associated risk factors such as hyperlipidemia and hyper- tension, and ameliorating insulin resistance. KGM has a demonstrated ability to modulate the rate of absorption of nutrients from the small bowel, whereas AG has postabsorptive effects. Consequently, it appears that KGM and AG are acting through different, yet complementary, mechanisms: KGM by increasing insulin sensitivity and AG likely by enhancing insulin secretion.

The glycemic and insulinemic increments with respect to type 2 diabetic subjects after a standard breakfast with glucomannan-enriched biscuits and common slices of toast containing the same amounts of carbohydrates and calories have been

evaluated. 49 The basal serum values of glucose and C-peptide were similar in the 2 days of the test. The mean increments of glucose and C-peptide were significantly

higher (p < 0.001) after slices of toast than after glucomannan-enriched biscuits. In conclusion, the results show a reduction in glycemic increments after breakfast with glucomannan-enriched biscuits. The decreased insulin secretion and the reduction of insulin need can preserve the functional reserve of beta-cells.

Seventy-two type 2 diabetic subjects were given konjac food for 65 days. The data analyzed by multiple F test indicate that the fasting blood glucose (FBG) and the 2-h postprandial blood glucose (PBG) on the 30th and 65th days after the food was ingested were significantly reduced (p = 0.001, p < 0.001, respectively), as was the glycosylated hemoglobin level at the end of the trial (p < 0.05). The final FBG and PBG of the subjects with an initial FBG (FBG-O) greater than 200 mg% decreased on the average by 51.8 and 84.6 mg%, respectively; those with an FBG- O of 150 to 200 mg% had decreases of 24.1 and 68.7 mg%; and those with an FBG- O less than 150 mg% had decreases of 4.8 and 21.4 mg%. No significant changes

Functional Food Carbohydrates

in blood lipid indexes were observed, except that the triglyceride values of subjects with hypertriglyceridemia (>200 mg%) significantly decreased by 118.7 mg%. It

was concluded that konjac food is very useful in the prevention and treatment of hyperglycemia. 50

The effects of the soluble fiber KGM on serum cholesterol concentrations were investigated in 63 healthy men in a double-blind crossover, placebo-controlled

study. 51 After a 2-week baseline period, the subjects were given 3.9 g of KGM or placebo daily for 4 weeks. After a washout period of 2 weeks, crossover took place, followed by another 4 weeks of treatment. The subjects were encouraged not to change their ordinary diets or general lifestyle during the investigation. KGM fibers reduced total cholesterol (TC) concentrations by 10% (p < 0.0001), low-density lipoprotein cholesterol (LDL-C) concentrations by 7.2% (p < 0.007), triglycerides by 23% (p < 0.03), and systolic blood pressure by 2.5% (p < 0.02). High-density lipoprotein cholesterol (HDL-C) and the ratio of LDL-C to HDL-C did not change significantly. No change in diastolic blood pressure or body weight was observed. No adverse effects were observed. The results of this study show that glucomannan is an effective cholesterol-lowering dietary adjunct.

Cairella et al. 52 studied the behavior of body weight, blood glucose, total serum cholesterol, and hunger and satiety sensation in 30 patients treated for 60 days with

a 1200-kcal diet plus either placebo or glucomannan. All the variables considered show that the low-calorie diet plus glucomannan is more effective than the low- calorie diet alone. Extensive clinical studies 53–55 have been carried out to clarify the effect of KGM fiber on obesity for children or adult patients. The results showed a significant mean weight loss using highly purified glucomannan after a period of treatment. Importantly, no significant side effects were observed in treated patients. On the basis of the marked ability to satiate patients and the positive metabolic effects, glucomannan diet supplements have been found to be particularly efficacious and well tolerated even in the long-term treatment of severe obesity.

Chronic constipation is a very frequent disease in Western countries. Recently, the efficacy and acceptability of glucomannans in 93 patients affected with chronic

constipation was tested. 56 The multicentric, open, and noncontrolled study was divided into an initial phase (treatment with 1 g of glucomannans t.i.d. for 1 month) and a maintenance phase (1 g b.i.d. for 1 month). Both objective parameters (number of days per week with bowel movements and number of enemas) and abdominal symptoms were evaluated. After one month, all assessed parameters showed a statistically significant improvement lasting through the second month. Glucoman- nans were well accepted and devoid of relevant side effects. In conclusion, consid- ering their efficacy and tolerability, they can be proposed as an ideal therapeutic tool in the management of chronic constipation symptoms.

Inadequate dietary fiber intake is a widely accepted explanation for chronic constipation in children with severe brain damage. To evaluate the efficacy of glucomannan as a treatment for chronic constipation, 20 children with severe brain damage and chronic constipation were randomly assigned to double-blind treatment with either glucomannan or placebo for 12 weeks. Stool habits, total and segmental gastrointestinal transit times, and anorectal motility were evaluated in all children before and after the treatment period. It was shown that glucomannan significantly

Konjac Glucomannan

increased stool frequency, whereas the effect of the placebo was not significant. Laxative or suppository use was significantly reduced by glucomannan but was not affected by the placebo. Clinical scores of stool consistency were significantly improved, and episodes of painful defecation per week were significantly reduced by glucomannan but not by the placebo. However, neither glucomannan nor the placebo had a measurable effect on total and segmental transit times. It seems that in neurologically impaired children, glucomannan improves stool frequency but has no effect on colonic motility. 57