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Traditional Chinese medicine

Barley sprout (mai ya)Hordeum vulgare

Sprouted barley, a digestion herb in Zhi Shi Xiao Pi Wan; the trials with numbers test a different barley fiber product in colitis (59 patients, 12 months).

Botanical name
Hordeum vulgare
Part used
germinated grain, dried (sometimes stir-baked)
Also called
pinyin Mai ya (麦芽); Malted barley, Barley malt, Hordei fructus germinatus
Used in
Traditional Chinese medicine
Taken for
Indigestion, Bloating, Appetite
Sold as
dried sprouted grain, powder, pills in formulas, decoction, granules

What is meant by barley sprout (mai ya)

Mai ya is barley (Hordeum vulgare) that has been allowed to germinate and is then dried, the same step by which brewers make malt. The Chinese pharmacopoeia name is Hordei Fructus Germinatus. In the pharmacy the sprouted grain is sold raw, stir-baked or charred, and it is used in decoctions, pills and granules, always as part of a formula in the texts we read. It is one of the ten ingredients of Zhi Shi Xiao Pi Wan, and the Pharmacopoeia of the PRC version of Bao He Wan lists it as well.

Do not confuse mai ya with germinated barley foodstuff, a fiber-and-protein product made from germinated barley and used in the colitis trials below. They share a source plant, but the trials tested the second and not the first. Germinated barley foodstuff is described in the trial papers as mainly dietary fiber and glutamine-rich protein, and it acts as a prebiotic that raises butyrate in the gut. A water extract of mai ya has been studied in the laboratory for an entirely different action, lowering the hormone prolactin, which is why the tradition also lists it for stopping milk.

In the traditions

Traditional Chinese medicine (about TCM)

Mai ya is classed in the Chinese materia medica as sweet and neutral, entering the spleen and stomach channels. The tradition says it promotes digestion and harmonizes the stomach, especially after meals heavy in starch or grain, and uses it for what the texts call food stagnation, with fullness, poor appetite and distension. Stir-baked or charred preparations are the usual choice for digestion in the texts. Large doses are listed for stopping the flow of breast milk, and texts advise caution in nursing women. In Zhi Shi Xiao Pi Wan it works with zhi shi, magnolia bark and pinellia against the stuffy fullness the texts call pi man. These are the tradition’s own classifications and not findings about the body.

What the plant contains

The sources we read do not itemize the constituents of mai ya. The better-documented laboratory and animal finding concerns a property that is not digestive: a water extract of the sprouted grain reduced prolactin secretion in rats given metoclopramide and in cultured pituitary cells, and the authors tie this to the dopamine D2 receptor and the cyclic AMP and protein kinase A pathway. That is a laboratory and animal finding on lactation hormones, not a measured digestive action. For the colitis trials, the germinated barley foodstuff is described as a prebiotic fiber that increases luminal butyrate by modulating the gut flora.

What has been tested in people

No trial of mai ya alone for dyspepsia turned up in our search. The numbers below are for germinated barley foodstuff (GBF) in ulcerative colitis, and for a formula that contains mai ya.

GBF, a fiber-and-protein product, was tested in ulcerative colitis. In an open multicenter trial, 21 patients with mild to moderate active disease took 20 to 30 g of GBF a day for 24 weeks alongside their usual treatment, and the clinical activity index fell, particularly visible blood in the stool and nocturnal diarrhea (P below 0.05 against a control group). In 59 patients in remission, 22 took 20 g a day for 12 months and 37 did not; clinical activity scores were better at 3, 6 and 12 months, and the cumulative recurrence rate in the steroid-tapering subgroup was lower. In a randomized trial of 46 patients in Iran, 30 g a day for two months lowered C-reactive protein within the group (P=0.017) and reduced abdominal pain and cramping (P=0.016); the other symptoms did not change significantly. None of these tested mai ya.

For the herb in its formula, a meta-analysis of 21 trials of Zhi Shi Xiao Pi decoction in functional dyspepsia found a higher total effective rate than Western medicine (odds ratio 3.54, 95% CI 2.49 to 5.05) with no significant difference in motilin, gastrin or gastric emptying measures; mai ya makes up 6 g of the 96 g prescription it tabulates. What has not been tested: mai ya alone, and GBF in functional gut disorders.

StudyDoseWhat it found
Open multicenter trial, 21 adults with mild to moderate active ulcerative colitis (germinated barley foodstuff, GBF) PMID 14532996GBF 20 to 30 g a day, 24 weeks, plus usual treatmentClinical activity index fell, especially visible blood in stool and nocturnal diarrhea (P below 0.05 vs control)
Controlled study, 59 ulcerative colitis patients in remission (22 GBF, 37 control) PMID 15067363GBF 20 g a day for 12 monthsBetter clinical activity index at 3, 6 and 12 months; lower cumulative recurrence in steroid-tapering group; no related side effects
Randomized trial, 46 ulcerative colitis patients (GBF vs control) PMID 25097845GBF 30 g a day for 2 months with routine medicinesCRP fell within the GBF group (P=0.017); abdominal pain and cramping reduced (P=0.016)
Meta-analysis of 21 trials of Zhi Shi Xiao Pi decoction (contains mai ya) in functional dyspepsia PMID 38809916Formula; 2 weeks to 2 monthsTotal effective rate OR 3.54 (95% CI 2.49 to 5.05) vs Western medicine; no significant difference in gastric emptying measures
Rat and cell study of Fructus Hordei Germinatus water extract on prolactin PMID 252540561 to 5 mg per mL in pituitary cells; rat dosesReduced prolactin secretion via dopamine D2 receptor pathway in metoclopramide-treated rats and cells

Doses used in trials and traditional preparations

No human trial of mai ya alone reports a dose. In the tabulated Zhi Shi Xiao Pi prescription the herb is 6 g, and the Bao He Wan version in the Pharmacopoeia lists 50 g of stir-baked malt in a batch with 300 g of charred hawthorn. In the colitis trials, germinated barley foodstuff was given at 20 g a day for 12 months, 20 to 30 g a day for 24 weeks, and 30 g a day for two months, but that is a different product. In the tradition the sprouts are decocted with other herbs or made into pills, raw or stir-baked.

Treat these figures as a record of what was studied. Whether any amount of barley sprout (mai ya) suits a particular person is a question for a clinician or pharmacist who knows their history.

Safety

The colitis trials of germinated barley foodstuff reported no side effects related to the product in two of the three papers read (the third did not state them in its abstract). Mai ya itself is a plant-food herb with a long traditional record, but our sources include no human safety data for it, and none for pregnancy. Two cautions apply. Barley contains gluten, so sprouted barley is not suitable for people who avoid gluten. And the tradition lists large doses of mai ya for stopping milk flow, supported in the laboratory by the prolactin finding, so women who are breastfeeding are the group the sources point to. For patent-medicine pills containing it, a review of Chinese proprietary medicines in Singapore tabulated excess toxic heavy metals and undeclared drugs reported in some such products from 1990 to 1997; that concerns the products it lists and not every pill.

Drug interactions

No drug interaction has been documented in the sources read. The laboratory finding is that a mai ya water extract lowered prolactin in rats treated with metoclopramide, a dopamine-blocking medicine that raises prolactin, through the dopamine D2 receptor pathway; whether this changes how medicines that act on dopamine behave in people has not been studied. The colitis trials gave germinated barley foodstuff alongside 5-aminosalicylate drugs and steroids without reported problems, but those trials used a different product.

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Questions people ask

Is mai ya the same as malt?

It is sprouted, dried barley, which is the same step by which brewers make malt. The pharmacy drug is sold raw, stir-baked or charred for use in decoctions and pills.

Is germinated barley foodstuff the same product?

No. The colitis trials tested germinated barley foodstuff, a fiber and glutamine-rich protein product, at 20 to 30 g a day. They share a source plant with mai ya, but the studies did not test mai ya.

Does the tradition caution nursing women?

Yes. TCM texts list large doses of mai ya for stopping breast milk, and a laboratory study found that a water extract lowered prolactin in rats and cells. No trial has tested it in breastfeeding women.

Has the formula it sits in been tested?

A meta-analysis of 21 trials of Zhi Shi Xiao Pi decoction, which includes mai ya, found a higher effective rate than Western drugs in functional dyspepsia, though it could not separate out the barley sprout.

Sources