IngredientesAgar, often called agar-agar (derived from the Malay word for seaweed), is a gelatinous substance extracted from specific species of red seaweed, primarily from the genera Gelidium and Gracilaria. It is also known as kanten (Japanese: 寒天, from the phrase kan-zarashi tokoroten, or "cold-exposed agar"), Japanese isinglass, China grass, Ceylon moss, and Jaffna moss. Gracilaria edulis, or its synonym G. lichenoides, is specifically referred to as agal-agal or Ceylon agar. As a food additive in the European Union, agar bears the designation E 406.
The algae used as agar sources are known as agarophytes. Gelidium yields the best quality of agar, but its cultivation is difficult and its natural resource is less abundant than Gracilaria, which is cultivated in several countries and regions on a commercial scale. Because Gelidium grows on rocky seabeds and requires turbulent water for a steady supply of nutrients and oxygen, it cannot be farmed. Gracilaria, the most abundant and promising resource for agar production, has probably more than 150 species, distributed mainly in the temperate and subtropical zones.
Agar is harvested from several species of red seaweed, particularly species in the Gelidium and Gracilaria families. These algae grow in coastal waters around the world, with major production in East Asia, South America, and parts of Europe and Africa. The seaweed is collected, cleaned, and boiled in water to release its gelling compounds, then filtered and dried into the forms seen on store shelves. The traditional Japanese process involves blending up to six or seven different types of red seaweed, selected according to the desired flexibility, density, smoothness, solidity, and resilience of the end product, with extraction in open iron cauldrons of boiling water. The extraction consists in boiling in autoclaves under pressure or in open tanks. The obtained extraction liquor contains about 2% agar-agar. It is filtered, then gelated. The obtained gel is dehydrated either by mechanical pressing through filtering cloth or by freeze-thawing at minus 20°C, which precipitates the agar.
Agar is available commercially in several distinct forms:
The application of agar as a food additive in Japan is alleged to have been discovered in 1658 by Mino Tarōzaemon, an innkeeper in current Fushimi-ku, Kyoto, who, according to legend, was said to have discarded surplus seaweed soup (Tokoroten) and noticed that it gelled after a winter night's freezing. Its Japanese name, kanten, translates to "cold sky," a reference to the traditional production method of freezing and thawing seaweed extract outdoors in winter air.
Tokoroten was popular as a summertime snack in the city of Edo, now Tokyo. Typically served cold in noodle-like strips, it is made by straining the broth of tengusa (Gelidium), then cooling the broth into a gelatinous solid. Agar has been used as food for several hundred years in China and Japan. It first appeared in the form of a jelly-like block, a form still available today. After World War II, Western countries began to industrialize the production of agar powder.
Macroalgae have been used widely as food by coastal cultures, especially in Southeast Asia. In the Philippines, Gracilaria, known as gulaman in Tagalog, has been harvested and used as food for centuries, eaten both fresh or sun-dried and turned into jellies. The earliest historical attestation is from the Vocabulario de la lengua tagala (1754) by the Jesuit priests Juan de Noceda and Pedro de Sanlucar, where golaman was defined as "una yerva, de que se haze conserva a modo de Halea, naze en la mar" ("a herb, from which a jam-like preserve is made, grows in the sea").
In Thailand, agar is popular for making various traditional desserts including wun na kati (coconut cream agar), wun chun (layered agar), and wun sangkhaya (custard agar). With its ability to form gels at low temperatures and remain stable even in hot climates, agar-agar is a widely popular ingredient globally for producing desserts, jellies, jams, and savory dishes.
In traditional Asian medicine, agar was employed primarily as a digestive aid and laxative. Agar-agar is approximately 80% dietary fiber, so it can serve as an intestinal regulator. Its bulking quality has been behind fad diets in Asia, for example the kanten (the Japanese word for agar-agar) diet. The substance was also used historically in the management of neonatal jaundice, a use that has been carried forward into limited clinical evaluation.
This was especially vexing to physician and bacteriologist Robert Koch, who, in seeking to culture his bacteria, sought a simple and consistently successful method. When microorganisms are streaked or plated onto agar's jellied surface and incubated, individual cells multiply into distinct colonies that scientists can easily observe, select, and propagate for further experiments. By 1905, a report on the seaweed industries in Japan noted the "very important use [of pure-grade agar] as a culture medium in bacteriological work." Agar was first subjected to chemical analysis in 1859 by the French chemist Anselme Payen, who had obtained agar from the marine algae Gelidium corneum.
During World War II, the War Production Board restricted American civilian use of agar in jellies, desserts, and laxatives so that the military could source a larger supply; it considered agar a "critical war material." World War II proved to be a decisive catalyst for the European agar industry. The shortage of Japanese agar during the war drove countries with coastal resources of Gelidium sesquipedale to begin their own production. Loureiro established the agar industry in Oporto, Portugal, while J. Mejias and F. Cabrero commenced studies in Spain — work that led directly to the establishment of the significant Iberian agar industry that continues today.
Agar is a linear polysaccharide extracted from agarophyte red algae and contains two fractions: neutral agarose and anionic agaropectin. The ratio of agarose to agaropectin polymers varies in agar obtained from different seaweed species. Natural agar constitutes at least two-thirds of agarose.
Araki showed that agar was formed by a mixture of two polysaccharides named agarose and agaropectin. The main structure of agarose is composed of repetitive units of β-D-galactose and 3,6-anhydro-α-L-galactose (3,6-AG), with few variations, and a low content of sulfate esters. Agarose has a high molecular mass above 100,000 Daltons, with a low sulfate content of below 0.15%. Agarose is a natural polymer and is responsible for the gelling property. Chemically, it is sulfate-free chains of linear molecules that occur as repeating alternate units of β-1,3-linked D-galactose and α-1,4-linked 3,6-anhydro-L-galactose.
Agaropectin is one of the two main components of agar. It is a sulfated galactan mixture which composes agar by approximately 30% composition. It is composed of varying percentages of organosulfates (sulfate esters), D-glucuronic acid, and small amounts of pyruvic acid. It is made up of alternating units of D-galactose and L-galactose heavily modified with acidic side-groups which are usually sulfate, glucuronate, and pyruvate. Agaropectin has a lower molecular mass below 20,000 Daltons, with a much higher sulfate content of 5% to 8%. Among these two fractions, agaropectin is a non-gelling compound responsible for the viscosity of agar.
Agar is soluble in boiling water but insoluble at lower temperatures, forming gels at 30–40°C. Agar can adopt a single or double helical conformation in a gel, creating a three-dimensional (3D) network that easily holds water molecules. The mechanism of gelation is based on the aggregation of helices and subsequent phase separation. The gelling property of agar depends on its composition and degree of sulfation. Generally, agar with higher agarose content and low degree of sulfation can form better and stronger gels. Agar is not broken down by microbial enzymes apart from a few species (including bacteria living in marine and freshwater habitats), and it dissolves well in boiling water, making it easy to sterilize.
Agar or agar-agar is a dry extract of red marine algae (seaweeds) which contains soluble fiber. It is used as a food additive and supplement. Agar is a mixture of indigestible polysaccharides agarose and agaropectin, which are composed of galactose units. Agar-agar is approximately 80% dietary fiber, so it can serve as an intestinal regulator.
Agar is essentially indigestible. The body cannot break it down the way it processes other carbohydrates, which is why it works as a bulk-forming laxative and appetite suppressant. It absorbs water and expands in the gut, adding volume to stool and promoting bowel movements. Once ingested, kanten triples in size and absorbs water. This results in consumers feeling fuller.
It was reported that soluble agar fibers delay gastric emptying and do not affect glycemic response. This effect is consistent with the known behavior of viscous soluble dietary fibers more broadly. Viscous fibers promote the reduction of the gastric emptying rate and/or glucose absorption through the intestinal mucosa.
Because agar forms a thick gel in the digestive tract, it can theoretically interfere with how well the body absorbs certain nutrients and medications. Agar products may delay stomach emptying time and reduce the absorption of some drugs, herbs, and supplements. It is advised that these agents and agar be taken at different times to minimize potential interactions.
Agar has a long history of use as a bulk-forming laxative. Agar capsules are sold as laxatives because of its supposed bulk-forming properties. While the mechanistic basis is well-supported — indigestible polysaccharides absorb water, increase stool volume, and stimulate intestinal transit — human clinical evidence specific to agar (as opposed to dietary fiber broadly) is limited. Most systematic reviews on dietary fiber and constipation have focused on psyllium, wheat bran, and other well-studied fibers rather than agar specifically.
Evidence strength: Mechanistically plausible; direct human RCT evidence for agar specifically is sparse.
In Japan, agar is called "kanten," and it is the main ingredient in "the kanten plan" or "the kanten diet." People use agar for obesity, diabetes, constipation, and other conditions, but there is no good scientific evidence to support these uses according to current assessments.
The most clinically significant study on agar and weight loss was published in Diabetes, Obesity and Metabolism (2005, Maeda et al.). The aim of this study was to evaluate the efficacy of agar diet in combination with a conventional diet (traditional Japanese food) for obese patients with impaired glucose tolerance and type 2 diabetes. After a 4-week run-in period on their habitual diets, 76 patients were randomly assigned to have conventional diet or conventional diet with agar. Both groups were on these diets for 12 weeks. Body weight, BMI, glycaemic control, blood pressure, insulin resistance, total body fat, fat distribution, and lipids were assessed before and after the experimental period. In both groups, after 12 weeks, mean body weight, BMI, fasting glucose levels, homeostasis model assessment-insulin resistance, and systolic and diastolic blood pressures had decreased significantly from their baseline values. The agar diet resulted in marked weight loss due to the maintenance of reduced calorie intake and to an improvement in metabolic parameters.
The major finding of this study was greater weight loss in the agar-supplemented group. However, the study involved a highly specific combined intervention (agar gel product "Slim Kanten" plus a traditional Japanese diet), making it difficult to isolate the contribution of agar alone. Agar tends to make people feel full, so they might stop eating earlier than they otherwise would. Some people think this reaction will lead to weight loss. But so far, there is not enough reliable scientific evidence that supports this weight loss theory.
Evidence strength: One small RCT (n=76) with promising results, but conducted within a specific cultural dietary context, making generalizability uncertain. Overall clinical evidence is preliminary and insufficient to draw firm conclusions.
Although long-term diet therapy with agar decreases fasting plasma glucose levels in diabetes, knowledge is lacking about the acute effects of agar on gastric emptying and the post-prandial glycaemic profiles. In healthy adults, agar and pectin delay gastric emptying but have no impact on the post-prandial glucose response. This finding from Sanaka et al. (2007) was based on a study of ten healthy male volunteers studied on three occasions with three different test meals (450 kcal/500 mL): a fibre-free meal; a meal with 2.0 g agar; or a meal with 5.2 g pectin. On each occasion, participants underwent a [¹³C]-acetate breath test along with serial blood sampling, and gastric emptying was quantified using half-excretion time and time for maximal excretion rate.
The same effect regarding both gastric emptying and glycemic response was seen in a more recent study by Clegg and Shafat (2014), where 11 subjects were given fruit-flavored jelly with 4 g of agar and 50 g of carbohydrates. The Maeda et al. (2005) RCT also reported significant reductions in fasting glucose and insulin resistance in the agar diet group over 12 weeks.
Evidence strength: Small human studies (n=10–76) indicate agar delays gastric emptying without acute glycemic effects; one RCT showed long-term glucose improvements in the context of a combined dietary intervention. Overall evidence is preliminary. No large, well-powered RCTs exist.
The objective of one review was to compile the effectiveness of algal polysaccharides, specifically agar, alginates, and carrageenan, in the prevention of cardiovascular disease (CVD), focusing on the pathophysiology underlying this group of diseases. The review also emphasized the benefits of dietary fiber consumption and its mechanisms of action throughout the gastrointestinal tract, including its relationship with intestinal health and CVD. Agar has been also used to lower blood cholesterol and glucose levels in individuals with diabetes mellitus. However, in some people, agar may also raise cholesterol.
Evidence strength: Mechanistic arguments exist, based on soluble fiber's known effects on bile acid sequestration and cholesterol absorption, but dedicated human RCT data for agar specifically are insufficient to support firm cardiovascular benefit claims.
An older area of investigation involved the use of agar in managing hyperbilirubinemia in neonates. The proposed mechanism is that agar's bulk-forming fiber properties would bind bilirubin in the gut and limit its enterohepatic recirculation, thereby reducing serum bilirubin levels. References to this use appear in the historical pharmacological literature (Romagnoli et al., cited in archival sources). Agar is possibly safe when given by mouth to infants with neonatal jaundice for up to 7 days. This application is now largely of historical interest and has not been incorporated into mainstream neonatal treatment guidelines.
Evidence strength: Historical case series and early studies; not supported by current clinical practice guidelines. Evidence is outdated and of low quality by modern standards.
The following dosages are drawn directly from published studies and should not be interpreted as recommendations:
Agar has been used as a food ingredient for centuries and is classified as Generally Recognized as Safe (GRAS) by the U.S. FDA under regulation 21 CFR 184.1115. Agar-agar is also affirmed as GRAS by the FDA for use as a stabilizer in animal drugs, feeds, and related products when used in accordance with good manufacturing or feeding practices under 21 CFR 582.7115. EFSA re-evaluated agar in 2016 and maintained approval with no numerical acceptable daily intake (ADI) specified — considered safe at current usage levels, with no safety concerns identified at typical dietary exposures. Both the European Food Safety Authority (EFSA) and the Joint FAO/WHO Expert Committee on Food Additives have reviewed the evidence and concluded that agar requires no numerical limit on daily intake because it poses no safety concern for the general population at typical dietary levels.
When the European Scientific Committee for Food evaluated agar in 1989, it found agar "devoid of toxicity at the highest dose levels tested" and saw no reason to set a maximum intake level. No reports of harmful effects on human health were found resulting from the use of agar.
This is the most clinically important safety consideration for agar taken as a supplement. When taken by mouth, agar is possibly safe for most adults when taken with at least one 8-ounce glass of water. If it is not taken with enough water, agar can swell and block the esophagus or bowel. Immediate medical attention is necessary if chest pain, vomiting, or difficulty swallowing or breathing occurs after taking agar. Consuming large amounts of dry agar powder without enough water can cause problems. The gel can swell in the esophagus or intestines before reaching the stomach, potentially leading to a blockage. This risk is most relevant if taking agar as a supplement in concentrated form rather than eating it in foods where it is already dissolved.
Agar should be avoided in patients with bowel obstruction or swallowing difficulties, as use may worsen esophageal or bowel obstruction, particularly when taken with insufficient amounts of fluid. Agar should be used with caution in individuals taking laxatives, as concurrent use may have additive effects.
There is not enough reliable information to know if agar is safe to use when pregnant or breastfeeding.
Phytobezoars, which are rarely occurring concentrations of fruit and vegetable fibers in the gastrointestinal tract, have been reported following ingestion of high-fiber foods such as agar.
Agar products may delay stomach emptying time and reduce the absorption of some drugs, herbs, and supplements. It is advised that these agents and agar be taken at different times to minimize potential interactions. Agar may lower blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar.
A small number of people are allergic to agar. Case reports date back to at least 1949, when a 35-year-old bakery worker developed worsening nasal congestion, sneezing, and asthma attacks from occupational exposure to agar. His symptoms were significantly worse while at work and progressed from nasal obstruction to full asthmatic episodes over the course of about a year. There have also been reports linking agar sensitivity to iodine sensitivity, since agar is derived from seaweed, which naturally contains iodine. These cases are uncommon enough that agar allergy does not appear on standard allergy panels.
Side effects may include gastrointestinal irritation, pain, and diarrhea when agar is given in powdered form in large doses. Agar may cause mild diarrhea and, theoretically, when ingested with insufficient fluid, esophageal or bowel obstruction.
Condiciones de salud que Agar puede ayudar a apoyar.
Agar is a soluble, gel-forming fiber that swells in the stomach, promoting satiety and potentially reducing caloric intake. The landmark Maeda et al. (2005) RCT found greater calorie reduction — particularly at the evening meal — in the agar diet group, suggesting appetite suppression. A separate RCT found agar jelly delayed gastric emptying compared to a matched liquid control, a mechanism associated with prolonged fullness.
Agar has been shown in a 12-week RCT to significantly reduce HbA1c and fasting glucose in obese patients with impaired glucose tolerance or type 2 diabetes. A separate human study examined agar's effect on postprandial glycaemic profiles. Evidence is limited to small trials but indicates a fiber-mediated attenuation of glucose excursions.
The Maeda et al. (2005) RCT showed significantly greater total cholesterol reduction in the agar group (−7.6 mg/dL) versus conventional diet (+2.4 mg/dL, p=0.036) over 12 weeks. HbA1c and total cholesterol decreased significantly within the agar group specifically. The proposed mechanism involves soluble fiber binding bile acids and reducing cholesterol reabsorption in the small intestine.
Agar functions as a bulk-forming agent: its gel matrix absorbs water in the colon, increases stool mass and softness, and promotes peristalsis. This mechanism is supported by documented use as a laxative and by the broader body of evidence that dietary fiber increases stool frequency in constipation. Agar has been listed in clinical references (WebMD, RxList) as a traditional laxative with this bulking mechanism.
Agar-derived oligosaccharides (agaro-oligosaccharides, agarotriose) have demonstrated prebiotic activity in vitro by selectively fermenting bifidobacteria and being degraded by gut Bacteroides species isolated from human feces. Human gut microbes capable of degrading agar polysaccharides have been identified in stool samples, establishing a biological interaction. In vitro and mechanistic evidence is strong, though human intervention trials specifically measuring microbiome shifts with agar are lacking.
The Maeda et al. (2005) RCT demonstrated significantly greater body weight loss (−2.8 kg vs. −1.3 kg) and BMI reduction (−1.1 vs. −0.5 kg/m²) in the agar group versus conventional diet over 12 weeks, alongside reductions in visceral fat, subcutaneous fat, and total body fat measured by DXA and CT. This is the strongest human evidence for agar's role in weight management.
The Maeda et al. (2005) RCT demonstrated that HOMA-IR (homeostatic model assessment of insulin resistance) decreased significantly in both groups, with the insulin area under the curve after OGTT declining significantly in the agar group specifically. Postprandial insulin levels decreased more significantly in the agar group than in controls, suggesting improved insulin sensitivity.
The Maeda et al. (2005) RCT demonstrated simultaneous improvements in multiple metabolic syndrome components — body weight, BMI, fasting glucose, HbA1c, HOMA-IR, blood pressure, total cholesterol, and body fat — in obese patients with glucose dysregulation consuming agar over 12 weeks. This multi-component improvement profile directly addresses the clustering of metabolic syndrome features.
Sistemas corporales que Agar puede ayudar a apoyar.
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