Yi Tang
StarN/A (processed product from grains including Oryza sativa L. and Hordeum vulgare L.)
Traditionally used for
- Cough & breathing
- Digestion
☯ TCM Properties
Tonifies the Middle and Augments Qi; Relaxes Spasms and Relieves Urgency; Moistens the Lungs and Stops Cough; Generates Fluids
Traditional Chinese Uses
Yi Tang (malt sugar, maltose) is a warm, sweet substance used in Chinese medicine to supplement the middle burner, relieve abdominal cramps and pain from deficiency cold, and soothe dry coughs. It warms and nourishes the Spleen and Stomach, moistens the Lungs, and relieves the spasmodic pain of intestinal or abdominal cramping from cold and deficiency. As the key ingredient in the classical Xiao Jian Zhong Tang formulation, it represents an important use of food-grade sweet substances in restoring digestive warmth and stopping pain.
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Botanical Description
Yi Tang is malt sugar (maltose syrup), a processed food-grade preparation rather than a plant. It is produced by sprouting barley or wheat to develop diastatic enzymes (chiefly beta-amylase), then combining the malted grain with steamed glutinous rice or another starchy substrate and incubating the mash at moderate temperature. The enzymes hydrolyse the starch into maltose, and the sweet liquid is strained, pressed from the spent grain, and boiled down to a thick amber-to-golden viscous syrup or, with further reduction, a soft chewy taffy-like solid. The colour ranges from pale honey to deep amber depending on duration of cooking. As a derived product Yi Tang lacks the morphology of a single botanical source and is catalogued in the Chinese materia medica as a sweet, warming, nutritive food-medicine.
Active Constituents
Maltose
Disaccharide (two glucose units joined alpha-1,4)Concentration: The predominant sugar of the preparation; it is the product the process is designed to make and gives the drug its English name of malt sugar
Hydrolysed at the intestinal brush border by maltase-glucoamylase and sucrase-isomaltase to two molecules of glucose, which are then absorbed by SGLT1. It is not a slow sugar: international glycaemic index tables place maltose at about 105 on the scale where glucose is 100, so a decoction dose behaves as rapidly available glucose rather than as a complex carbohydrate.
Limit dextrins
Branched glucose oligosaccharides (partial starch hydrolysates)Concentration: A substantial minor fraction, arising because barley beta-amylase cannot hydrolyse past the alpha-1,6 branch points of amylopectin
The residue left when malt beta-amylase has stripped maltose from the outer chains of the grain starch and stalls at the branch points. These give the syrup its body and viscosity, and are digested more slowly than maltose by glucoamylase and isomaltase, contributing a smaller and later glucose load.
Maltotriose
Trisaccharide (three glucose units joined alpha-1,4)Concentration: A minor oligosaccharide of malt-saccharified starch syrup
An intermediate of incomplete starch hydrolysis, cleaved by brush border glucoamylase to glucose plus maltose. It behaves essentially as a slightly slower source of the same glucose load.
Glucose
MonosaccharideConcentration: Present as a minor free sugar; the amount depends on how far saccharification was carried
Free glucose in the syrup needs no digestion and is absorbed directly, so it is the fastest-acting fraction. Its proportion varies with the manufacturing process, which is one reason the drug's glycaemic effect is not precisely predictable batch to batch.
Grain protein and amino acids
Protein and free amino acids (residual cereal matter)Concentration: Trace residues carried over from the rice or barley starting material
Small residues from the grain and the malt. They are the reason the drug is not chemically identical to a purified maltose solution, but there is no evidence that they contribute to its clinical effect. Anyone with coeliac disease should note that the barley malt starting material is a gluten source.
⚠ Drug Interactions
Acarbose
Acarbose competitively inhibits the brush border alpha-glucosidases glucoamylase, sucrase, maltase and isomaltase, and it inhibits maltase more potently than miglitol does. Maltose is therefore the exact substrate acarbose is designed to block. Giving a maltose preparation to a patient on acarbose leaves the disaccharide undigested in the lumen, where it draws water osmotically and is fermented by colonic bacteria, producing the flatulence, bloating and diarrhoea already characteristic of the drug. The sugar also cannot deliver the nourishing effect the prescription intends, because it is never absorbed.
Clinical note: Do not prescribe Yi Tang to a patient taking acarbose or another alpha-glucosidase inhibitor. If the patient is already on both and has diarrhoea, remove the Yi Tang before adjusting the drug. Substitute a non-disaccharide sweet tonic such as Da Zao or honey-fried Gan Cao if the formula requires one.
Miglitol
Miglitol inhibits the same brush border alpha-glucosidases as acarbose, though maltase somewhat less potently. In mice, miglitol given with maltose produced late-phase GLP-1 secretion in a GLUT2-dependent manner and significantly greater GLP-1 release than acarbose plus maltose, because miglitol additionally activates SGLT3 and stimulates duodenal enteroendocrine cells. The combination of this drug with a maltose preparation is thus both a malabsorption problem and an unpredictable incretin stimulus.
Clinical note: Treat as for acarbose and avoid the combination. If a patient on miglitol reports unusually severe gastrointestinal symptoms after starting a Chinese formula, check whether Yi Tang is in it.
Miglustat
Miglustat causes reversible inhibition of intestinal disaccharidases including maltase and sucrase, and this, rather than any effect on beta-galactosidases, is the established cause of the carbohydrate malabsorption that limits its tolerability. Adding a preparation whose principal constituent is maltose delivers more of exactly the substrate that cannot be hydrolysed.
Clinical note: Avoid Yi Tang in patients on miglustat, who are typically already managing diet to control diarrhoea. The interaction is a nuisance rather than a danger, but it can be enough to make a patient stop a drug they need.
Insulin, sulfonylureas and other glucose-lowering therapy
Maltose is hydrolysed to two glucose molecules at the brush border and international glycaemic index tables place it above pure glucose, at about 105. Classical use is not a token amount: in Xiao Jian Zhong Tang the malt sugar is the chief ingredient, dosed by the cup and stirred into the strained decoction, and modern dosing of the drug is in tens of grams. This is a rapidly available carbohydrate load given repeatedly, which is straightforwardly incompatible with fixed-dose insulin or sulfonylurea regimens.
Clinical note: Treat Yi Tang as dietary carbohydrate and count it as such. In insulin-treated diabetes it needs the dose to be covered or the herb to be omitted; in sulfonylurea-treated patients, omit it. Do not assume that because it is prescribed as a herb it can be ignored in the carbohydrate count.
Aspirin and other NSAIDs
Xiao Jian Zhong Tang, in which Yi Tang is the chief ingredient, reduced aspirin-induced gastric mucosal injury in mice, cutting mucosal injury area and epithelial apoptosis dose-dependently, restoring the tight junction proteins ZO-1 and occludin and correcting aspirin-driven redox imbalance. A second study in the same model attributed the effect to regulation of TNF-alpha signalling, with cinnamaldehyde from the Gui Zhi in the formula identified by molecular docking as a key compound. The evidence is animal and formula-level, and the docking result points at a co-ingredient rather than at the malt sugar itself.
Clinical note: This is a reason not to fear the combination, not a reason to rely on it. Do not present the formula as gastroprotection for a patient on long-term aspirin, and do not let it substitute for a proton pump inhibitor where one is indicated.
Patients with congenital sucrase-isomaltase deficiency or acquired disaccharidase deficiency
Maltose depends on maltase-glucoamylase and sucrase-isomaltase at the brush border, so both congenital sucrase-isomaltase deficiency and the acquired disaccharidase loss that follows villous injury from coeliac disease, gastroenteritis or chemotherapy leave it unhydrolysed. The resulting osmotic diarrhoea mimics, and may be mistaken for, the digestive weakness the formula was prescribed to treat, so the herb can appear to be failing when it is in fact causing the symptom.
Clinical note: Ask about lifelong carbohydrate intolerance before prescribing. If diarrhoea or bloating starts or worsens after a Yi Tang-containing formula, withdraw the herb as a trial rather than escalating the dose. Note also that the barley malt used to make it is a gluten source, which matters in coeliac disease.
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
The middle is warmed and tonified while spasm is relaxed, relieving abdominal pain from deficiency cold.
Core pair of a classical formula — Xiao Jian Zhong Tang, Shang Han Lun (Zhang Zhongjing)
Evidence Tier
Moderate evidence · 3 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
0
Other clinical trial
0
Observational / case report
0
In vitro / animal
3
1 verified · 2 unverified
Show 3 studies
- Distinct action of the alpha-glucosidase inhibitor miglitol on SGLT3, enteroendocrine cells, and GLP1 secretion
- Xiaojianzhong decoction attenuates aspirin-induced gastric mucosal injury via the PI3K/AKT/mTOR/ULK1 and AMPK/ULK1 pathways
- Mechanism of Xiaojianzhong decoction in alleviating aspirin-induced gastric mucosal injury revealed by transcriptomics and metabolomics
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Distinct action of the alpha-glucosidase inhibitor miglitol on SGLT3, enteroendocrine cells, and GLP1 secretion
GLP-1 was measured in murine portal vein after oral carbohydrate. Miglitol given with maltose evoked late-phase GLP-1 secretion in a GLUT2-dependent manner, and significantly more than acarbose plus maltose, even though acarbose inhibits maltase more potently; the difference was traced to miglitol activating SGLT3 and stimulating duodenal enteroendocrine cells, which acarbose does not. Miglitol alone triggered no secretion, so the maltose is required. This is the direct evidence that maltose is the substrate through which alpha-glucosidase inhibitors act, and that the two drugs of that class differ in what happens when it is given.
Xiaojianzhong decoction attenuates aspirin-induced gastric mucosal injury via the PI3K/AKT/mTOR/ULK1 and AMPK/ULK1 pathways
C57BL/6 mice in six groups of ten received aspirin 300 mg/kg with Xiaojianzhong decoction at 12, 6 or 3 g/kg, omeprazole 20 mg/kg, or water, by gavage for 14 days. The decoction reduced gastric mucosal injury area by 83.4, 22.6 and 11.3 percent at the three doses and epithelial apoptosis by 40.8, 25.4 and 8.7 percent, raised ZO-1 and occludin, shifted autophagy markers, activated PI3K/AKT/mTOR/ULK1 and inhibited AMPK/ULK1, and offset the aspirin-induced redox imbalance. Yi Tang is the chief ingredient of this formula, but the study does not isolate its contribution from that of the other five ingredients.
Mechanism of Xiaojianzhong decoction in alleviating aspirin-induced gastric mucosal injury revealed by transcriptomics and metabolomics
In the same aspirin gastric injury model, the decoction reduced inflammation, preserved the mucosal barrier, lowered apoptosis and necroptosis and promoted repair, with the mechanism attributed to regulation of TNF-alpha signalling and to correction of amino acid metabolism. Molecular docking singled out cinnamaldehyde as a key active compound, which comes from the Gui Zhi in the formula and not from the malt sugar. Read alongside the companion study, this is formula-level animal evidence and should not be transferred to Yi Tang as a single agent.
Historical Texts
Shang Han Lun (Treatise on Cold Damage), Zhang Zhongjing
Eastern Han dynasty, c. 200 to 220 CEJin Gui Yao Lue (Essentials from the Golden Cabinet), Zhang Zhongjing
Eastern Han dynasty, c. 200 to 220 CEBen Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming dynasty, 1578References
- Foster-Powell K, Holt SHA, Brand-Miller JC. International table of glycemic index and glycemic load values: 2002 . The American Journal of Clinical Nutrition (2002) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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