Agar Information - Side Effects, Uses and Benefits

Common Trade Names

Multi-ingredient preparations: Agarbil, Agoral, Agoral Plain, Demosvelte-N, Falqui, Lexat, Paragar, Pseudophage

Common Forms

Available as a dry powder and in flakes and strips.

Source

Agar is an aqueous extract from the cell walls of various species of red algae, including Gelidium cartilagineum and Gracilaria conservatives.

Chemical Components

Agar is composed primarily of the calcium salt of a sulfuric acid ester of the complex polysaccharide agarose-agropectin. The powdered form is soluble in boiling water. The resultant solution gels when cool, even at concentrations as low as 5%.

Actions

The pharmacokinetics of agar have not been well studied in humans. Poorly absorbed from the GI tract, agar promotes fecal bulk and may influence absorption of dietary minerals, proteins, and fat.

In one study, five patients were placed on a high-fiber diet (agar­agar) for 5 days. During that time, protein and fat digestibility was markedly decreased and fecal excretion of cholesterol increased.

In animal studies, rats fed 10% agar-agar experienced reduced absorption of calcium, iron, zinc, copper, chromium, and cobalt. A notable increase in fecal dry matter indicated that agar was not absorbed . The results of other animal studies show that agar decreases protein digestibility and reduces nitrogen retention . These effects may result from partial breakdown of agar by intestinal flora and a resultant inhibition of proteolytic enzymes.

Reported Uses

Agar has long been used as a culture medium in bacteriology. It is also used as an emulsifying and suspending agent in many pharmaceutical and food products. Agar was formerly used frequently as a bulk­forming laxative. It has been found to be less effective than phototherapy and phenobarbital in the treatment of neonatal hyperbilirubinemia .

Dosage

As a bulk-forming laxative, 4 to 16 g P.O. once daily or b.i.d.

Adverse Reactions

GI: bowel obstruction, esophageal obstruction.

Metabolic: decreased absorption of vitamins, minerals, and nutrients (especially calcium, iron, zinc, copper, chromium, and cobalt). Respiratory: aspiration (when administered with insufficient liquids).

Interactions

Alcohol: Dehydration and precipitation of agar from solutions. Avoid use with agar.

Electrolyte solutions: Partial dehydration and decreased viscosity of agar solutions. Avoid use with agar.

Tannic acid: Precipitation of agar from solutions. Avoid use with agar.

Contraindications And Precautions

Agar is contraindicated in patients with impaired consciousness (because of aspiration risk) and in pregnant or breast-feeding patients. Use cautiously in patients with a history of esophageal or bowel obstruction, throat problems, or difficulty swallowing.

Special Considerations

Bowel and esophageal obstruction are potential risks. Instruct the patient to take this herb with plenty of water (at least 8 oz) to minimize the risk of obstructions and aspiration.

Advise the patient to report abdominal pain; chest pain, tightness, or pressure; difficulty swallowing or breathing; or vomiting to his health care provider.

Inform the patient that products containing agar should be taken on an empty stomach to minimize the risk of decreased absorption of vitamins and minerals.

Advise the patient to anticipate a change in the bulk and appearance of stools. If appropriate, offer a stool softener to patients who might have difficulty tolerating increased fecal bulk.

Commentary

Because no long-term human studies have assessed agar's effects on mineral and nutrient absorption and because more effective agents, such as syllabub, are available, products that contain agar should not be routinely used to treat constipation.