Glucomannan
Encyclopedia
Glucomannan is a water-soluble polysaccharide
that is considered a dietary fiber
. Glucomannan is a food additive
used as an emulsifier and thickener. Products containing glucomannan, marketed under a variety of brand names, are also sold as nutritional supplements for constipation
, obesity
, high cholesterol, acne vulgaris
and type 2 diabetes
. Although there is some clinical support for potential health benefits, the U.S. Food and Drug Administration (FDA) has not approved any product containing glucomannan for the treatment of these medical conditions. Several companies selling products containing glucomannan have been disciplined by the U.S. Federal Trade Commission
(FTC) for misleading or exaggerated claims pertaining to the health benefits of glucomannan supplements.
and D-glucose
in a ratio of 1.6:1. The degree of branching is about 8% through β-(1→6)-glucosyl linkages.
Glucomannan with α-(1→6)-linked galactose
units in side branches is called galactoglucomannan
.
, of the konjac
plant. It is also a hemicellulose
that is present in large amounts in the wood of conifers and in smaller amounts in the wood of dicotyledon
s.
of obese patients. In healthy men, 4 weeks of taking 3.9 grams of glucomannan decreased total cholesterol, low-density lipoprotein, triglyceride
s, and systolic blood pressure; notably, triglycerides dropped by 23%. Glucomannan has also been tested in children with high cholesterol in conjunction with a diet. Interestingly, greater decreases in total cholesterol and low-density lipoprotein were observed in female children when compared to male children. When used in conjunction with chitosan
, glucomannan decreases serum cholesterol possibly by increasing steroid
excretion via the feces
.
An 8 week double blind trial involved 20 obese patients. A placebo or a glucomannan fiber supplement of 1 gram was given to the subjects one hour before each meal. No changes were made to the diet or exercise habits of the patients. The study found that over the 8 week period, cholesterol levels were significantly reduced, and the Glucomannan group had an average weight loss of 5.5 lbs.
, glucomannan is used as an emulsifier and thickener. It has E number
E425(ii).
products marketed via television advertisements claiming to aid in weight loss
. According to the FTC, there are no clinical data supporting many of the claims and several companies have been determined by the FTC or the FDA to have, at some time, violated the Federal Food, Drug, and Cosmetic Act
including Vitacost
, PediaLean, Herbal Worldwide Holdings, BioTrim, and others. The company Obesity Research Institute, the marketer of FiberThin, Zylotrim, Propolene and Lipozene, settled FTC charges that their misleading weight-loss claims violated federal laws by agreeing to pay $1.5 million in consumer redress.
In 2002, a number of products containing konjac-derived glucomannan were recalled as choking hazards.
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
that is considered a dietary fiber
Dietary fiber
Dietary fiber, dietary fibre, or sometimes roughage is the indigestible portion of plant foods having two main components:* soluble fiber that is readily fermented in the colon into gases and physiologically active byproducts, and* insoluble fiber that is metabolically inert, absorbing water as it...
. Glucomannan is a food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...
used as an emulsifier and thickener. Products containing glucomannan, marketed under a variety of brand names, are also sold as nutritional supplements for constipation
Constipation
Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...
, obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
, high cholesterol, acne vulgaris
Acne vulgaris
Acne vulgaris is a common human skin disease, characterized by areas of skin with seborrhea , comedones , papules , pustules , Nodules and possibly scarring...
and type 2 diabetes
Diabetes mellitus type 2
Diabetes mellitus type 2formerly non-insulin-dependent diabetes mellitus or adult-onset diabetesis a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency. Diabetes is often initially managed by increasing exercise and...
. Although there is some clinical support for potential health benefits, the U.S. Food and Drug Administration (FDA) has not approved any product containing glucomannan for the treatment of these medical conditions. Several companies selling products containing glucomannan have been disciplined by the U.S. Federal Trade Commission
Federal Trade Commission
The Federal Trade Commission is an independent agency of the United States government, established in 1914 by the Federal Trade Commission Act...
(FTC) for misleading or exaggerated claims pertaining to the health benefits of glucomannan supplements.
Chemistry
Glucomannan is mainly a straight-chain polymer, with a small amount of branching. The component sugars are β-(1→4)-linked D-mannoseMannose
Mannose is a sugar monomer of the aldohexose series of carbohydrates. Mannose is a C-2 epimer of glucose. It is not part of human metabolism, but is a component of microbial cell walls, and is therefore a target of the immune system and also of antibiotics....
and D-glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
in a ratio of 1.6:1. The degree of branching is about 8% through β-(1→6)-glucosyl linkages.
Glucomannan with α-(1→6)-linked galactose
Galactose
Galactose , sometimes abbreviated Gal, is a type of sugar that is less sweet than glucose. It is a C-4 epimer of glucose....
units in side branches is called galactoglucomannan
Galactoglucomannan
Galactoglucomannan is a water-soluble hemicellulose, consisting of galactose, glucose and mannose. Many softwood species, e.g. Norway spruce are rich of galactoglucomannans and can contain it up to 10-20% -Structure:...
.
Natural sources
Glucomannan comprises 40% by dry weight of the roots, or cormCorm
A corm is a short, vertical, swollen underground plant stem that serves as a storage organ used by some plants to survive winter or other adverse conditions such as summer drought and heat ....
, of the konjac
Konjac
Konjac , also known as konjak, konjaku, konnyaku potato, devil's tongue, voodoo lily, snake palm, or elephant yam , is a plant of the genus Amorphophallus...
plant. It is also a hemicellulose
Hemicellulose
A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...
that is present in large amounts in the wood of conifers and in smaller amounts in the wood of dicotyledon
Dicotyledon
The dicotyledons, also known as dicots, are a group of flowering plants whose seed typically has two embryonic leaves or cotyledons. There are around 199,350 species within this group...
s.
Potential health risk
A health advisory was released by Health Canada stating the following: "natural health products containing the ingredient glucomannan in tablet, capsule or powder form, which are currently on the Canadian market, have a potential for harm if taken without at least 8 ounces of water or other fluid. The risk to Canadians includes choking and/or blockage of the throat, esophagus or intestine, according to international adverse reaction case reports. It is also important to note that these products should NOT be taken immediately before going to bed."Constipation
Glucomannan is a soluble fiber, and as such, has been investigated for the treatment of constipation. Glucomannan may relieve constipation by decreasing fecal transit time. In the treatment of chronic constipation, glucomannan significantly improved symptoms of constipation while being well-tolerated and free of relevant side effects.Cholesterol and other lipids
Glucomannan has demonstrated statistically significant improvements in the total cholesterolCholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...
of obese patients. In healthy men, 4 weeks of taking 3.9 grams of glucomannan decreased total cholesterol, low-density lipoprotein, triglyceride
Triglyceride
A triglyceride is an ester derived from glycerol and three fatty acids. There are many triglycerides, depending on the oil source, some are highly unsaturated, some less so....
s, and systolic blood pressure; notably, triglycerides dropped by 23%. Glucomannan has also been tested in children with high cholesterol in conjunction with a diet. Interestingly, greater decreases in total cholesterol and low-density lipoprotein were observed in female children when compared to male children. When used in conjunction with chitosan
Chitosan
Chitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine...
, glucomannan decreases serum cholesterol possibly by increasing steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
excretion via the feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
.
Type 2 diabetes
Glucomannan may be useful as a therapeutic adjunct for type 2 diabetes. It has been shown to improve the lipid profile and alleviate the fasting blood glucose levels of type 2 diabetics.Weight Loss
In one study involving 200 obese subjects, Glucomannan or a placebo were given for 16 weeks. They found that Glucomannan & fiber group lost 4.52 kg on average compared to 0.79 of control group. The Glucomannan group also had increased satiety compared to control group. LDL cholesterol was significantly reduced as well during the 16 week period. The study also reported that the treatments were well tolerated, and did not report any side effects.An 8 week double blind trial involved 20 obese patients. A placebo or a glucomannan fiber supplement of 1 gram was given to the subjects one hour before each meal. No changes were made to the diet or exercise habits of the patients. The study found that over the 8 week period, cholesterol levels were significantly reduced, and the Glucomannan group had an average weight loss of 5.5 lbs.
Commercial use
As a food additiveFood additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...
, glucomannan is used as an emulsifier and thickener. It has E number
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...
E425(ii).
Dietary supplements
Glucomannan is an ingredient in a variety of dietary supplementDietary supplement
A dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to supplement the diet and provide nutrients, such as vitamins, minerals, fiber, fatty acids, or amino acids, that may be missing or may not be consumed in sufficient quantities in a person's diet...
products marketed via television advertisements claiming to aid in weight loss
Weight loss
Weight loss, in the context of medicine, health or physical fitness, is a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue...
. According to the FTC, there are no clinical data supporting many of the claims and several companies have been determined by the FTC or the FDA to have, at some time, violated the Federal Food, Drug, and Cosmetic Act
Federal Food, Drug, and Cosmetic Act
The United States Federal Food, Drug, and Cosmetic Act , is a set of laws passed by Congress in 1938 giving authority to the U.S. Food and Drug Administration to oversee the safety of food, drugs, and cosmetics. A principal author of this law was Royal S. Copeland, a three-term U.S. Senator from...
including Vitacost
Vitacost
Vitacost.com is a leading online retailer and direct marketer of health and wellness products includinge dietary supplements such as vitamins, minerals, herbs or other botanicals, amino acids and metabolites, as well as cosmetics, organic body and personal care products, sports nutrition and ...
, PediaLean, Herbal Worldwide Holdings, BioTrim, and others. The company Obesity Research Institute, the marketer of FiberThin, Zylotrim, Propolene and Lipozene, settled FTC charges that their misleading weight-loss claims violated federal laws by agreeing to pay $1.5 million in consumer redress.
In 2002, a number of products containing konjac-derived glucomannan were recalled as choking hazards.
External links
- PDRhealth.com Glucomannan Studies Glucomannan studies, with information on side effects.