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IUPAC name β(1→4)-d-gluco-d-mannoglycan | |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Glucomannan is a water-soluble polysaccharide that is considered a dietary fiber. It is a hemicellulose component in the cell walls of some plant species. Glucomannan is a food additive used as an emulsifier and thickener. It is a major source of mannan oligosaccharide (MOS) found in nature, the other being galactomannan, which is insoluble. [1]
Products containing glucomannan, under a variety of brand names, are marketed as dietary supplements with claims they can relieve constipation and help lower cholesterol levels. [2] [3] Since 2010 they are legally marketed in Europe as helping with weight loss for people who are overweight and eating a diet with restricted calories, [3] but as of 2020 [update] there was no good evidence that glucomannan helped weight loss. [4] [5] Glucomannan lowers LDL cholesterol by 10 percent. [6]
Supplements containing glucomannans pose a risk for choking and bowel obstruction if they are not taken with sufficient water. [7] Other adverse effects include diarrhea, belching, and bloating; in one study people taking glucomannans had higher triglyceride levels. [8]
Glucomannans are also used to supplement animal feed for farmed animals, to cause the animals gain weight more quickly.
Glucomannan is mainly a straight-chain polymer, with a small amount of branching. The component sugars are β-(1→4)-linked D-mannose and D-glucose in a ratio of 1.6:1. [9] The degree of branching is about 8% through β-(1→6)-glucosyl linkages. [10]
Glucomannan with α-(1→6)-linked galactose units in side branches is called galactoglucomannan.[ citation needed ]
In the yeast cell wall, mannan oligosaccharides are present in complex molecules that are linked to the protein moiety. There are two main locations of mannan oligosaccharides in the surface area of Saccharomyces cerevisiae cell wall. [11]
They can be attached to the cell wall proteins as part of –O and –N glycosyl groups and also constitute elements of large α-D-mannanose polysaccharides (α-D-Mannans), which are built of α-(1,2)- and α-(1,3)- D-mannose branches (from 1 to 5 rings long), which are attached to long α-(1,6)-D-mannose chains. [12] [13]
This specific combination of various functionalities involves mannan oligosaccharides-protein conjugates and highly hydrophilic and structurally variable 'brush-like' mannan oligosaccharides structures that can fit to various receptors of animal digestive tracts, [14] and to the receptors on the surface of bacterial membranes, [15] impacts these molecules' bioactivity. Mannan oligosaccharides-protein conjugates are involved in interactions with the animal's immune system and as result enhance immune system activity. [16] They also play a role in animal antioxidant and antimutagenic defense. [17]
Glucomannan comprises 40% by dry weight of the roots, or corm, of the konjac plant. Another culinary source is salep, ground from the roots of certain orchids and used in Greek and Turkish cuisine. However, these orchid species are protected in the whole EU and the trade of salep is strictly forbidden. Glucomannan is also a hemicellulose that is present in large amounts in the wood of conifers and in smaller amounts in the wood of dicotyledons.[ citation needed ] Glucomannan is also a constituent of bacterial, plant and yeast cell wall with differences in the branches or glycosidic linkages in the linear structure. [18] [19] [20]
Glucomannan is a food additive used as an emulsifier and thickener with the E number E425(ii). [21] [22]
Glucomannan-rich salep powder is responsible for the unique textural properties of salep dondurma, a mastic-flavored stretchable and chewy ice cream of Turkish origin. [23]
Konjac, also rich in glucomannan, is widely used for its jelly-like texture. It found use in shirataki noodles, in fruit jellies snacks (with choking risk), [24] and as a substitute for gelatin.
Glucomannan is an ingredient in a variety of dietary supplement products marketed with claims that they aid in weight loss, but medical research has found no good evidence to support its use for this purpose. [4] [5] The claim is that it makes a gel when mixed with water, which can take up space in the stomach and linger there longer than water alone would, inducing a person to feel full after having eaten a smaller amount of food. [8]
In Europe and Canada, glucomannan dietary supplements can be marketed with claims to lower cholesterol levels and to relieve constipation. [2] [3]
Data from a randomized controlled clinical trial suggests that glucomannan dietary supplements help regulate the hormone ghrelin and might help control appetite in people with Type 2 diabetes. [25]
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 250 ml or 8 ounces of water or other fluid. The risk 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." [7]
Other adverse effects include diarrhea, belching, and bloating; in one study people taking glucomannans had higher triglyceride levels. [8]
Several companies have been determined by the Federal Trade Commission (FTC) or the Food and Drug Administration (FDA) to have, at some time, violated the Federal Food, Drug, and Cosmetic Act. [26] The companies include Vitacost, [27] PediaLean, [28] Herbal Worldwide Holdings, [29] BioTrim, [30] 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. [31]
In 2001, a number of jelly-type candy products containing konjac-derived glucomannan were barred from import by the U.S. Food and Drug Administration due to choking hazards. [32]
It is also used as dietary supplement for farmed animals in order to help them gain more weight from food, called the feed conversion ratio. The effect of mannan oligosaccharides on animal performance was analysed in meta-analyses for poultry, [33] [34] [35] pigs, [36] [37] and calves. [38]
A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 and thus with the empirical formula Cm(H2O)n, which does not mean the H has covalent bonds with O. However, not all carbohydrates conform to this precise stoichiometric definition, nor are all chemicals that do conform to this definition automatically classified as carbohydrates.
Cholesterol is the principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils.
Omega−3 fatty acids, also called Omega−3 oils, ω−3 fatty acids or n−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond, three atoms away from the terminal methyl group in their chemical structure. They are widely distributed in nature, being important constituents of animal lipid metabolism, and they play an important role in the human diet and in human physiology. The three types of omega−3 fatty acids involved in human physiology are α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). ALA can be found in plants, while DHA and EPA are found in algae and fish. Marine algae and phytoplankton are primary sources of omega−3 fatty acids. DHA and EPA accumulate in fish that eat these algae. Common sources of plant oils containing ALA include walnuts, edible seeds, and flaxseeds as well as hempseed oil, while sources of EPA and DHA include fish and fish oils, and algae oil.
Polysaccharides, or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with water (hydrolysis) using amylase enzymes as catalyst, which produces constituent sugars. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch, glycogen and galactogen and structural polysaccharides such as cellulose and chitin.
Pantothenic acid (vitamin B5) is a B vitamin and an essential nutrient. All animals need pantothenic acid in order to synthesize coenzyme A (CoA)—essential for metabolizing fatty acid—and to synthesize and metabolize proteins, carbohydrates, and fats.
Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vitamin E, can cause nerve problems. Vitamin E is a fat-soluble antioxidant which may help protect cell membranes from reactive oxygen species. Worldwide, government organizations recommend adults consume in the range of 3 to 15 mg per day. As of 2016, consumption was below recommendations according to a worldwide summary of more than one hundred studies that reported a median dietary intake of 6.2 mg per day for alpha-tocopherol.
Tocopherols are a class of organic compounds comprising various methylated phenols, many of which have vitamin E activity. Because the vitamin activity was first identified in 1936 from a dietary fertility factor in rats, it was named tocopherol, from Greek τόκοςtókos 'birth' and φέρεινphérein 'to bear or carry', that is 'to carry a pregnancy', with the ending -ol signifying its status as a chemical alcohol.
Dietary fiber or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition, and can be grouped generally by their solubility, viscosity, and fermentability, which affect how fibers are processed in the body. Dietary fiber has two main components: soluble fiber and insoluble fiber, which are components of plant-based foods, such as legumes, whole grains and cereals, vegetables, fruits, and nuts or seeds. A diet high in regular fiber consumption is generally associated with supporting health and lowering the risk of several diseases. Dietary fiber consists of non-starch polysaccharides and other plant components such as cellulose, resistant starch, resistant dextrins, inulin, lignins, chitins, pectins, beta-glucans, and oligosaccharides.
Mannans are polymers containing the sugar mannose as a principal component. They are a type of polysaccharide found in hemicellulose, a major source of biomass found in higher plants such as softwoods. These polymers also typically contain two other sugars, galactose and glucose. They are often branched.
A dietary supplement is a manufactured product intended to supplement a person's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources, or that are synthetic. The classes of nutrient compounds in supplements include vitamins, minerals, fiber, fatty acids, and amino acids. Dietary supplements can also contain substances that have not been confirmed as being essential to life, and so are not nutrients per se, but are marketed as having a beneficial biological effect, such as plant pigments or polyphenols. Animals can also be a source of supplement ingredients, such as collagen from chickens or fish for example. These are also sold individually and in combination, and may be combined with nutrient ingredients. The European Commission has also established harmonized rules to help insure that food supplements are safe and appropriately labeled.
Mannose is a sugar monomer of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylation of certain proteins. Several congenital disorders of glycosylation are associated with mutations in enzymes involved in mannose metabolism.
An oligosaccharide is a saccharide polymer containing a small number of monosaccharides. Oligosaccharides can have many functions including cell recognition and cell adhesion.
Prebiotics are compounds in food that foster growth or activity of beneficial microorganisms such as bacteria and fungi. The most common environment considered is the gastrointestinal tract, where prebiotics can alter the composition of organisms in the gut microbiome.
Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanols. More than 250 sterols and related compounds have been identified. Free phytosterols extracted from oils are insoluble in water, relatively insoluble in oil, and soluble in alcohols.
β-Hydroxy β-methylbutyric acid (HMB), otherwise known as its conjugate base, β-hydroxyβ-methylbutyrate, is a naturally produced substance in humans that is used as a dietary supplement and as an ingredient in certain medical foods that are intended to promote wound healing and provide nutritional support for people with muscle wasting due to cancer or HIV/AIDS. In healthy adults, supplementation with HMB has been shown to increase exercise-induced gains in muscle size, muscle strength, and lean body mass, reduce skeletal muscle damage from exercise, improve aerobic exercise performance, and expedite recovery from exercise. Medical reviews and meta-analyses indicate that HMB supplementation also helps to preserve or increase lean body mass and muscle strength in individuals experiencing age-related muscle loss. HMB produces these effects in part by stimulating the production of proteins and inhibiting the breakdown of proteins in muscle tissue. No adverse effects from long-term use as a dietary supplement in adults have been found.
Nutrition and pregnancy refers to the nutrient intake, and dietary planning that is undertaken before, during and after pregnancy. Nutrition of the fetus begins at conception. For this reason, the nutrition of the mother is important from before conception as well as throughout pregnancy and breastfeeding. An ever-increasing number of studies have shown that the nutrition of the mother will have an effect on the child, up to and including the risk for cancer, cardiovascular disease, hypertension and diabetes throughout life.
Red yeast rice, red rice koji, red fermented rice, red kojic rice, red koji rice, anka, or angkak, is a bright reddish purple fermented rice, which acquires its color from being cultivated with the mold Monascus purpureus. Red yeast rice is what is referred to as a "koji" in Japanese, meaning "grain or bean overgrown with a mold culture", a food preparation tradition going back to ca. 300 BC. In both the scientific and popular literature in English that draws principally on Japanese traditional use, red yeast rice is most often referred to as "red rice koji." English language articles favoring Chinese literature sources prefer the translation "red yeast rice."
Cholesterol absorption inhibitors are a class of compounds that prevent the uptake of cholesterol from the small intestine into the circulatory system. Most of these molecules are monobactams but show no antibiotic activity. An example is ezetimibe Another example is Sch-48461. The "Sch" is for Schering-Plough, where these compounds were developed. Phytosterols are also cholesterol absorption inhibitors.
Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and for many other biological effects. In humans, the most important compounds in this group are vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol).
Oat β-glucans are water-soluble β-glucans derived from the endosperm of oat kernels known for their dietary contribution as components of soluble fiber. Due to their property to lower serum total cholesterol and low-density lipoprotein cholesterol, and potentially reduce the risk of cardiovascular diseases, oat β-glucans have been assigned a qualified health claim by the European Food Safety Authority and the US Food and Drug Administration.
MOS is often prepared by hydrolysis reaction of a mannose-contained glucan polymer, mainly glucomannan and galactomannan.
GM appears generally safe, but there is insufficient evidence to suggest its efficacy in weight loss
The more recent meta-analysis by Onakpoya et al. [58] revealed a non-statistically significant difference of −0.22 kg in weight loss between the glucomannan and placebo groups, contradicting the earlier meta-analysis. These conflicting results might be explained by the different inclusion criteria that the studies used to select the clinical trials analyzed. Although Sood et al. [59] found a statistically significant reduction in weight among study participants using glucomannan, this weight loss is not necessarily clinically significant; thus, the results should be interpreted carefully.
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