ID 3725 -
Glukomannan
PL: Glukomannan
EN: Glucomanan
Pdf: konjac mannan
Oświadczenie (4)
- Glukomannan przyczynia się do zmniejszenia masy ciała w połączeniu z zastosowaniem diety niskokalorycznej
Oświadczenie (2)
- przyczynia się do wagi ciała
- wagi ciała
1. Charakterystyka żywności / składnika
The food constituent that is the subject of the health claims is glucomannan. Glucomannan (konjac mannan) is a water-soluble type of fibre composed of a straight chain of β-1→4 D-mannose and D- glucose units in a ratio of 1.6:1 with a small amount of branching (8 %) through β-(1→6)-glucosyl linkages. It is derived from the tuberous roots of the konjac plant (Amorphophallus konjac K. Koch). Glucomannan is non-digestible in the human small intestine. It has a high molecular weight (200-2000 kDa) and high viscosity in water solution. Glucomannan does not occur naturally in foods. It is a food additive used as an emulsifier and a thickener, and is also consumed in the form of food supplements (Katsuraya et al., 2003).
The Panel considers that the food constituent, konjac mannan (glucomannan), which is the subject of the health claims, is sufficiently characterised.
2.1. Redukcja masy ciała (ID 854, 1556, 3725)
The claimed effects are “weight management” and “contributes to weight management”. The Panel assumes that the target population is overweight individuals.
In the context of the proposed wordings, the Panel assumes that the claimed effects refer to the reduction of body weight.
Weight loss in overweight subjects, even without achieving a normal body weight, is considered to be a beneficial physiological effect.
The Panel considers that reduction of body weight is a beneficial physiological effect for overweight individuals.
3.1. Redukcja masy ciała (ID 854, 1556, 3725)
A total of 45 references were cited for the scientific substantiation of this claim. Among them, six reported on intervention studies in humans investigating the effects of glucomannan on body weight (Birketvedt et al., 2005; Cairella and Marchini, 1995; Vido et al., 1993; Vita et al., 1992; Vuksan et al., 1999; Walsh et al., 1984). Also, the Panel identified three additional references cited in relation to other claims on glucomannan as being pertinent to this claim (Wood et al., 2007; Chen et al., 2003; Vuksan et al., 2001).
Walsh et al. (1984) conducted an eight-week double-blind, placebo-controlled, randomised trial in 20 obese subjects, who were randomly assigned to consume either glucomannan or placebo (starch) administered as 1 g doses (two capsules of 500 mg each) with 8 oz of water three times per day (before each meal) for eight weeks in the context of usual dietary patterns and levels of physical
exercise. Body weight loss during the study was significantly higher in the glucomannan group
(-5.5 1.5 kg) than in the placebo group (1.5 1.5 kg; difference between groups 7.0 1.4 kg, p<0.005).
In a double-blind, placebo-controlled randomised intervention study (Cairella and Marchini, 1995), 30 overweight women (BMI=25-30 kg/m2) were treated for 60 days with a 1,200 kcal/d (5,040 kJ/d) diet plus either placebo (n=15) or glucomannan (n=15). A total of four capsules of glucomannan or placebo were given daily with 1-2 glasses of water 30-60 minutes prior to the two main meals (appr. 4 g per day). Body weight loss during the study was statistically significantly (p=0.0017) higher in the glucomannan group (-4.3 kg) than in the placebo group (-2.7 kg, mean difference 1.6 kg, 95%CI=0.7-2.5).
In a double-blind, placebo-controlled randomised intervention study (Birketvedt et al., 2005), healthy overweight subjects were randomly assigned to consume either glucomannan (n=23) or placebo (n=29) for five weeks in the context of an energy-reduced diet providing 1,200 kcal per day. Glucomannan (1.24 g per day) and placebo were administered in tablets (n=6) with 250 mL of water 15 minutes before each meal (three times daily) and at 3 pm (n=4 tablets). Weight loss during the
intervention was significantly higher in the glucomannan group (-3.8 0.9) than in the placebo group
(-2.5 0.5, p<0.01).
In the study by Vita et al. (1992), 50 obese subjects (15 males) were randomly assigned to consume a hypocaloric diet (1,000 kcal/d or 4,200 kJ/d for women and 1,300 kcal or 5,460 kJ/d for men) either alone (control, n=25, 8 males) or together with glucomannan supplements (2+3+3 capsules with 300 mL water before meals, appr. 4 g per day in three doses) for three months. The authors reported a greater weight loss in the glucomannan group compared to controls at the end of the study (p<0.02) expressed as percentage of initial body weight from baseline. Mean changes are given as a histogram (approx. -25 % versus -20 % of initial body weight in the glucomannan and placebo groups respectively) and SD are not reported.
In a double-blind, placebo-controlled randomised intervention study (Vido et al., 1993), 60 overweight children under the age of 15 (mean age 11.2 years) were randomised to consume glucomannan (two capsules with two glasses of water one hour prior to each meal, 2 g/d, n=30) or placebo (n=30) for two months in the context of a normocaloric diet. The percentage of children being overweight significantly decreased during the study in both the intervention and the placebo groups with no significant differences between groups. No differences between groups in body weight changes were observed at the end of the study.
In a cross-over randomised controlled trial (RTC), 11 non diabetic, mildly hypertensive, free-living subjects with the insulin resistance syndrome (out of 278 subjects screened) consumed, in random order, test biscuits with glucomannan (0.5 g of glucomannan per 100 kcal of dietary intake, 8-13 g per day) or wheat bran fibre control biscuits for three weeks each separated by a 2-week washout (Vuksan et al., 2000). No statistically significant differences in body weight changes were observed between the glucomannan and the wheat bran fibre (control) interventions. In another study by the same authors with identical design, no statistically significant differences in body weight changes were observed between the glucomannan and the wheat bran fibre (control) interventions in a group of 11 type 2 diabetic subjects (Vuksan et al., 1999). The Panel notes the small number of subjects included in these studies, the short study duration, and that glucomannan was not given as pre-load before the meals but was rather consumed with the meals.
In a parallel-arm, double-blind, placebo-controlled intervention study by Wood et al., (2007), 30 overweight and obese men were randomly assigned to consume either glucomannan (3 g/d, n=15) or placebo (n=15) for 12 weeks in the context of a carbohydrate restricted diet for weight loss. No statistically significant differences in body weight changes were observed between the glucomannan and the placebo groups.
In the study by Chen et al. (2003), 22 diabetic subjects (12 female) with elevated blood cholesterol concentrations received, following a randomised, double-blind, crossover design, glucomannan and placebo (starch) for 28 days each with no washout period in between. Glucomannan and placebo were administered in gelatine capsules with a glass of water three times daily half an hour prior to meals. The dose of glucomannan increased progressively from 1.2 (for three days), 2.6 (for three days) to 3.6 g per day (for 22 days). No statistically significant differences in body weight changes were observed between the glucomannan and placebo groups. The Panel notes the short duration of the study and the absence of a washout period between interventions.
The Panel notes that no long-term studies (>3 months) on the effects of glucomannan on body weight are available.
The Panel also notes that glucomannan is a soluble-type of fibre which forms a viscous, gel-like mass in the stomach when hydrated, and that this “mass effect” could delay gastric emptying and induce satiety leading to a decrease in subsequent energy intake (Keithley and Swanson, 2005).
In weighing the evidence, the Panel took into account that most of the intervention studies, which were of adequate sample size and duration, found a statistically significant effect of glucomannan on body weight loss in the context of a hypocaloric diet when administered as a pre-load before meals, and that the mechanism by which glucomannan could exert the claimed effect is established.
Panel concludes that a cause and effect relationship has been established between the consumption of glucomannan and the reduction of body weight in the context of an energy-restricted diet.
4.1. Redukcja masy ciała (ID 854, 1556, 3725)
The Panel considers that the following wording reflects the scientific evidence: “Glucomannan contributes to the reduction of body weight in the context of an energy-restricted diet”.
5.1. Redukcja masy ciała (ID 854, 1556, 3725)
The Panel considers that in order to obtain the claimed effect, at least 3 g of glucomannan should be consumed daily in three doses of at least 1 g each, together with 1-2 glasses of water before meals, in the context of an energy-restricted diet. The target population is overweight adults.
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