Traditional Use and the Silk Road

Almost every plant in a herbal shop travelled because people wanted it. White mulberry travelled because a caterpillar wanted it.

Bombyx mori, the domesticated silkworm, will eat mulberry leaves and essentially nothing else. Silk is worth a fortune. Therefore, wherever anyone anywhere decided to make silk, they first had to plant mulberry trees — in China, across Central Asia, into Persia, India, Byzantium, Italy, France, and eventually the Americas. The tree is now naturalised on every continent except Antarctica, and it got there riding an insect’s appetite.

That story is charming on its own. What makes it worth an article on a health site is that the chemistry and the history turn out to be the same story. DNJ — the molecule that blunts your post-meal glucose spike — is the mulberry tree’s chemical weapon against caterpillars. It is in the leaf to poison insects. And the silkworm, alone among caterpillars, evolved a gut enzyme that ignores it entirely.

The molecule that stops a caterpillar digesting sugar is the molecule that slows you digesting sugar. The silkworm beat it. You have not.

Table of Contents

  1. A Tree That Travelled Because of an Insect
  2. The Poison in the Leaf
  3. How the Silkworm Beat It
  4. Where Sericulture Began — and a 2026 Revision
  5. The Silk Road Was a Mulberry Road
  6. Europe’s Mulberry Obsession
  7. 桑葉 Sang Ye in Chinese Medicine
  8. What the Tradition Did Not Claim
  9. Japan, Korea and Vietnam: Tea, Vegetable, Medicine
  10. The Epilogue: An Invasive Tree in North America
  11. What History Can and Cannot Tell You
  12. Key Research Papers
  13. Connections

A Tree That Travelled Because of an Insect

Morus alba L. is a fast-growing deciduous tree of the Moraceae — the fig and breadfruit family — native to northern and central China, where it has been cultivated for several thousand years. Left alone it reaches ten to twenty metres. In a silk operation it is never left alone: it is coppiced hard to a shrubby two metres so that leaves can be stripped by hand, quickly, in enormous quantity.

The reason for all that stripping is Bombyx mori, and Bombyx mori is a remarkable animal. It is one of only a handful of fully domesticated insects, and domestication has left it helpless: the adult moth has wings it cannot fly with, no functional mouthparts, and no ability to survive outside human care. There is no wild population. Its closest wild relative, Bombyx mandarina, still lives on mulberry in East Asia.

The larva is a specialist feeder. It will accept mulberry and, at a stretch, a few close relatives such as Cudrania and Osage orange — all in the same family — but mulberry is what it thrives on. Its feeding is famously driven by leaf chemistry: mulberry volatiles and specific compounds trigger biting and swallowing behaviour, which is why decades of effort to raise silkworms on artificial diets have always had to include mulberry leaf powder.

The economics follow immediately. Producing a kilogram of raw silk takes a very large quantity of mulberry leaf and tens of thousands of cocoons. A silk industry is therefore, first and always, an agricultural enterprise: plantations, pruning cycles, leaf logistics, and a workforce whose year is organised around leaf flush. To acquire silk production you had to acquire the tree, and you had to acquire it in bulk.

This is why mulberry is one of the most widely transplanted trees in the world, and why its distribution map looks less like an ecological range and more like a record of human ambition.

The Poison in the Leaf

For most of the history above, everyone assumed mulberry leaf was simply good food. Silkworms grow beautifully on it; therefore it must be nutritious and benign. That assumption held until someone asked the obvious question in reverse: if mulberry leaf is such excellent caterpillar food, why do so few other caterpillars eat it?

A Japanese research group answered that in 2006, in a paper whose title says it plainly: Mulberry latex rich in antidiabetic sugar-mimic alkaloids forces dieting on caterpillars.

Snap a mulberry leaf and a milky sap oozes from the broken veins. That latex is the tree’s defence, and the researchers showed it directly. Mulberry leaves were highly toxic to caterpillars other than Bombyx mori. Remove the latex from the leaves and the toxicity disappeared. Add latex to an artificial diet and the toxicity came with it.

Then they analysed what was in it. The latex was loaded with alkaloidal sugar-mimic glycosidase inhibitors — the very compounds already known for antidiabetic activity:

And the concentrations were extraordinary. In several mulberry varieties these inhibitors reached 1.5–2.5 percent of the latex — 8 to 18 percent of its dry weight, roughly one hundred times the concentrations previously reported for whole mulberry leaves.

Read that again, because it reframes the entire supplement. The whole-leaf figures of 0.05 to 0.3 percent DNJ that determine what a mulberry capsule can deliver are the diluted average of a leaf whose latex canals are carrying a concentrated insecticide. The tree is not producing DNJ for you. It is producing an anti-herbivore poison, and you are consuming a heavily diluted trace of it.

The logic of the weapon is elegant. A caterpillar’s diet is almost entirely leaf carbohydrate, and it must digest sucrose to grow. A sugar-mimic that jams its digestive enzymes does not kill it outright — it starves it slowly. Hence the title: the latex forces the caterpillar to diet.

How the Silkworm Beat It

Which leaves the obvious question. If mulberry latex is a broad-spectrum caterpillar poison, how does the silkworm eat nothing else?

A 2007 follow-up answered it with a clean comparison. The researchers fed two caterpillars — Bombyx mori, the mulberry specialist, and Samia ricini, the Eri silkworm, a generalist that eats many plants — diets containing different sugars, with and without the sugar-mimic alkaloids from mulberry latex.

In the generalist S. ricini, adding the alkaloids to a sucrose diet reduced both growth and sugar absorption. In B. mori, it reduced neither.

Then they measured the enzyme itself, and the numbers are startling:

That is a difference of more than two orders of magnitude, and in the alkaloid-fed generalist the compounds turned up in the haemolymph — the insect equivalent of blood — with disrupted trehalose levels to match.

The silkworm did not detoxify the poison. It rebuilt the lock so the key no longer fits. Its digestive sucrase is an enzyme that sugar-mimic alkaloids simply cannot bind. That single adaptation is what let one caterpillar monopolise a tree defended well enough to exclude everyone else — and, downstream of that, is why silk exists as a human industry at all.

The circle closes here. Your intestinal α-glucosidases are the unadapted version. They bind DNJ exactly as the generalist caterpillar’s does. The mechanism described in Blood Sugar and Post-Meal Spikes is, in evolutionary terms, you being treated as a herbivore — a very mild version of the effect the tree intends for a caterpillar, and one you can now buy in a capsule.

Where Sericulture Began — and a 2026 Revision

The received account is straightforward: sericulture began in China, was guarded as a state secret for millennia, and spread west along the Silk Road roughly two thousand years ago. Chinese tradition assigns its invention to Leizu, consort of the Yellow Emperor, who supposedly discovered silk when a cocoon fell into her tea — a foundation myth, not a date.

Chinese origin is not in doubt. The timing and the route west now are.

In July 2026, a multidisciplinary team reported micromorphological and proteomic analysis of three cocoons excavated at Sapalli Tepe in Uzbekistan, a Bronze Age site of the Oxus civilisation. The cocoons were identified as Bombyx mori and directly radiocarbon dated to 1940–1765 cal. BCE — the earliest Bombyx cocoon remains known. The same site produced the earliest mulberry (Morus sp.) charcoal yet found in Central Asia.

Together those two findings mean mulberry-and-silkworm sericulture was being practised in the Oxus region nearly two thousand years earlier than previously documented — long before there was any Silk Road to carry it. The authors suggest silkworms and mulberry trees may have reached Central Asia along the southern slope of the Himalayas, while noting other routes remain plausible.

Two caveats belong here, because this is very new work. It rests on three cocoons from one site, and single-site findings are revised more often than they are confirmed. And the authors themselves present the route as a hypothesis rather than a conclusion. But the dating is direct, the species identification is by protein mass spectrometry rather than morphology alone, and the mulberry charcoal corroborates it. It is a serious result.

Related work has complicated the picture from the other direction: protein mass spectrometry on ancient silks has revealed the use of wild silk species in antiquity, meaning not every early silk find implies domesticated Bombyx and a mulberry plantation behind it. The history of silk is being actively rewritten, and anyone telling you it is settled is a century out of date.

The Silk Road Was a Mulberry Road

Whatever its origin, silk became the commodity that organised Eurasian trade — and because silk cannot be made without mulberry, the diffusion of silk production is a map of mulberry planting.

China. Silk was a state industry, a tax, a currency and a diplomatic instrument. Bolts of silk paid soldiers and bought peace with steppe confederations. Techniques were protected; exporting silkworm eggs was, by tradition, a capital offence.

Korea and Japan. Sericulture crossed east early and became deeply embedded. Japan would eventually build a national economy on it — by the late nineteenth century raw silk was the country’s dominant export, and the mechanised Tomioka Silk Mill, opened in 1872 and now a UNESCO World Heritage site, is the monument to that transformation. Whole regions of rural Japan were reorganised around mulberry fields and household silkworm rearing.

Central Asia and Persia. The oasis cities of the Oxus and the Fergana Valley became silk centres in their own right rather than mere waypoints. Merv, Bukhara and Samarkand traded in it; Persian workshops developed distinctive weaving traditions. The 2026 Sapalli Tepe finding suggests this region’s involvement is far older than its role as a transit corridor.

India. Sericulture arrived and diversified. India remains a major silk producer today, and is unusual in producing several non-mulberry silks — tasar, eri and muga — from wild and semi-domesticated moths that feed on other trees entirely.

Byzantium. The best-known transfer story comes from the historian Procopius, who records that around 552 CE two monks brought silkworm eggs to the Emperor Justinian from the East, concealed in hollow canes. Whether the detail is literal or embroidered, Byzantine silk production was genuinely established in the sixth century and became an imperial monopoly — and it required mulberry plantations in Greece and Asia Minor to sustain it.

One consequence deserves emphasis. Every one of these transfers required moving two living things: an insect that cannot survive without human care, and a tree that takes years to reach productive size. Silk technology could not be stolen in a single act. It had to be planted and waited for.

Europe’s Mulberry Obsession

From Byzantium, sericulture moved into the Mediterranean, and for six centuries European states pursued it with an intensity that is hard to overstate.

Italy. Sicily and Calabria took it up under Arab and then Norman rule. By the medieval period Lucca was a European silk capital, later joined by Florence, Venice, Genoa and Milan. Northern Italian agriculture was reshaped: mulberry trees were planted along field margins and irrigation channels across Lombardy and the Veneto, and silk became a household industry running alongside farming.

France. Louis XI encouraged silk at Tours in the fifteenth century; the industry found its permanent home at Lyon, which became the dominant European silk city. Under Henri IV, at the turn of the seventeenth century, the crown promoted mulberry planting as national policy — hundreds of thousands of trees, with the aim of ending France’s dependence on Italian imports. Lyon’s silk workers, the canuts, later became one of the defining industrial workforces of nineteenth-century Europe.

England. The most instructive failure. In 1608–1609 James I promoted a national silk scheme, distributing mulberry trees and urging landowners to plant them. It failed. The explanation usually given is that the trees planted were largely Morus nigra, the black mulberry — a species grown for its far superior fruit, but poor silkworm fodder compared with M. alba. The story is repeated everywhere and is probably part of the truth; historians have also pointed to the English climate, the absence of skilled labour, and competition from established Italian and French producers. Either way, the scheme left England with a legacy of venerable black mulberry trees in old gardens and no silk industry whatsoever.

Colonial America. The same ambition crossed the Atlantic. The Virginia Company required colonists to plant mulberry; Georgia was chartered partly as a silk colony and put a mulberry leaf and silkworm on its seal. The Carolinas and Connecticut tried too. In the 1830s the United States experienced an outright speculative bubble in Morus multicaulis, a mulberry variety promoted as the key to an American silk industry; the mania collapsed in 1839, ruining investors and leaving behind a great many surplus mulberry trees.

That last fact matters for the epilogue below.

桑葉 Sang Ye in Chinese Medicine

Alongside the silk economy, the same tree accumulated a distinct medical identity. Mulberry appears in the Shennong Bencao Jing, the foundational Chinese materia medica compiled around the first to second century CE.

Chinese medicine treats four parts of the mulberry tree as four separate drugs, which is a useful discipline that consumer marketing routinely ignores:

The leaf is classified as cool in nature, sweet and bitter in taste, entering the Lung and Liver channels. Its classical indications are:

Its best-known formula is Sang Ju Yin — Mulberry Leaf and Chrysanthemum Decoction — which pairs sāng yè with chrysanthemum flower for exactly that early wind-heat cough. Sang Xing Tang pairs it with apricot kernel for dry autumn cough.

Classical practice specifies 霜桑葉 — frost-touched leaf, collected after the first autumn frost. Modern analysis points the other way for DNJ specifically: the Japanese work that produced DNJ-enriched powder found the highest content in young leaves from the tops of branches in summer. A tea made to the classical specification and an extract made to maximise DNJ are therefore not the same product, harvested at different times for different reasons. Neither is wrong; they are aimed at different targets.

What the Tradition Did Not Claim

Here is the part most articles about mulberry leaf get backwards, and it is worth being precise about.

Blood sugar is essentially absent from the classical picture. Diabetes as we understand it did not exist as a category in classical Chinese medicine. The nearest concept, xiāo kě — “wasting-thirsting disorder,” describing excessive thirst, hunger, urination and weight loss — was generally treated with other herbs. Mulberry leaf’s traditional indications are respiratory, febrile and ophthalmic. They are not metabolic.

The modern use came from chemistry, not tradition. DNJ was characterised in the 1960s and 1970s; Japanese and Chinese researchers investigated mulberry leaf as a source; the α-glucosidase mechanism was worked out; and the human postprandial trials followed from the 1990s onward. Miglitol, a DNJ derivative, became a licensed drug.

This is the reverse of the usual herbal narrative. The familiar story is “traditional healers used it for X, and modern science confirmed X.” Here it is: modern science found an interesting molecule, traced it to a plant that traditional medicine had been using for something else entirely, and built a new indication from scratch.

Being clear about this actually helps mulberry leaf’s case. Its blood-sugar claim does not rest on the argument-from-antiquity that so often substitutes for evidence. It rests on an identified molecule, a defined enzyme target, a licensed drug analogue, and human trials with dose-response. That is a stronger foundation than four thousand years of anything.

The corollary is uncomfortable but honest: the traditional uses — cough, sore throat, eye complaints, night sweats — have almost no human trial evidence. They rest on clinical tradition plus a modest amount of cell and animal work. They may well be reasonable. They are not demonstrated.

Japan, Korea and Vietnam: Tea, Vegetable, Medicine

Sericulture also left a food culture behind it, which is a substantial part of why mulberry leaf’s safety record for ordinary consumption is as good as it is.

Japan. Kuwa-cha (桑茶), mulberry leaf tea, has been drunk for centuries — mild, faintly grassy, caffeine-free. Modern Japan markets it specifically for post-meal blood sugar, and mulberry leaf powder appears in soba noodles, mochi, ice cream and confectionery for its green colour as much as its function. Some products are marketed on GABA content, which mulberry leaf accumulates and which anaerobic processing can raise considerably. Treat those claims sceptically: orally consumed GABA crosses the blood–brain barrier poorly, and a calming effect from drinking it is not established.

Korea. Ppongnip-cha (뽕잎차) is drunk similarly, and mulberry leaf appears in health foods and traditional preparations. Korea has an old and continuous sericulture tradition of its own.

Vietnam. Mulberry is cây dâu tằm, the leaf lá dâu tằm — literally “silkworm mulberry leaf,” with the insect built into the plant’s name. In thuốc nam, Vietnamese folk medicine, it is used for coughs, night sweats and eye complaints. Young leaves are also eaten as a vegetable, blanched or added to soups — a use that sits squarely between food and medicine. The Red River Delta has a long sericulture history.

China. 桑叶茶 is drunk as a cooling summer tea, and mulberry leaf is a standard pharmacy item. The tree is also, still, an enormous agricultural crop: China remains the world’s dominant silk producer.

One consistent thread: across all four cultures, the leaf is consumed as a mild everyday drink or vegetable, in quantities delivering small and unmeasured amounts of DNJ. That is a genuinely reassuring safety history. It is not a history of taking concentrated standardised extracts three times a day, which is a modern practice with a modern, and much shorter, evidence base.

The Epilogue: An Invasive Tree in North America

All those colonial mulberry plantings, and the collapsed Morus multicaulis speculation of the 1830s, left behind millions of white mulberry trees in a continent that never developed a silk industry.

Morus alba turned out to be an excellent invader. It grows fast, fruits heavily, tolerates poor soil and urban conditions, and its fruit is spread widely by birds. Across much of the eastern and central United States it is now classified as an invasive species, colonising disturbed ground, roadsides and forest edges.

The more serious problem is genetic. Morus rubra, the red mulberry, is native to eastern North America — and it hybridises freely with introduced M. alba. Introgression from the far more abundant white mulberry is a recognised threat to red mulberry, which is listed as endangered in Canada. It is a slow extinction by interbreeding rather than by clearance.

That has a practical consequence for anyone buying mulberry leaf products, and it is not a small one. Hybrids are common, and identifying mulberries by leaf shape is notoriously unreliable — a single tree carries plain heart-shaped leaves and deeply three- or five-lobed ones simultaneously. Meanwhile Morus nigra, M. australis, M. indica, M. macroura and M. bombycis are all used regionally, and only M. alba is the species behind essentially all the DNJ research.

Which is why the very first line of the label checklist in How to Take It is the botanical name. A four-thousand-year history of cultivation and two centuries of enthusiastic hybridisation have left “mulberry” a much vaguer word than it looks.

What History Can and Cannot Tell You

Traditional use is history, not proof. But history is not worthless either, and it is worth being clear about which parts of it carry weight.

What the history does support:

What it does not support:

The best summary of this plant may be the one the biology already gave us. Mulberry makes DNJ to stop caterpillars digesting sugar. It works — on caterpillars, and, mildly, on us. The silkworm evolved past it and got a tree to itself; humans noticed the effect three thousand years later and put it in a capsule. Everything in these four articles is a footnote to that.

Key Research Papers

Every identifier below was verified live against NCBI E-utilities — title, first author, journal and year all had to match before a PMID was printed. Historical claims that are not the subject of indexed research are presented as history, with topic searches and general resources rather than false citations.

The chemistry behind the story

  1. Konno K, Ono H, Nakamura M, Tateishi K, et al. Mulberry latex rich in antidiabetic sugar-mimic alkaloids forces dieting on caterpillars. Proceedings of the National Academy of Sciences USA. 2006;103(5):1337–1341. Insect ecology. Latex alkaloids at 1.5–2.5 percent (8–18 percent dry weight), ~100× whole-leaf concentrations; toxic to caterpillars but not to B. mori.
  2. Hirayama C, Konno K, Wasano N, Nakamura M. Differential effects of sugar-mimic alkaloids in mulberry latex on sugar metabolism and disaccharidases of Eri and domesticated silkworms: enzymatic adaptation of Bombyx mori to mulberry defense. Insect Biochemistry and Molecular Biology. 2007;37(12):1348–1358. Insect physiology. Midgut sucrase IC50 0.9–8.2 µM in S. ricini versus >1,000 µM in B. mori.
  3. Yatsunami K, Ichida M, Onodera S. The relationship between 1-deoxynojirimycin content and alpha-glucosidase inhibitory activity in leaves of 276 mulberry cultivars (Morus spp.) in Kyoto, Japan. Journal of Natural Medicines. 2008;62(1):63–66. Analytical. Why cultivar and harvest month change the product.
  4. Song W, Wang HJ, Bucheli P, Zhang PF, et al. Phytochemical profiles of different mulberry (Morus sp.) species from China. Journal of Agricultural and Food Chemistry. 2009;57(19):9133–9140. Analytical. Species differ chemically — the identification problem, quantified.

Sericulture, silk and archaeology

  1. Zhou X, Shen H, Li Z, Spengler RN, et al. Silkworm cultivation predating the Silk Road in southern Central Asia (2000 BCE). Science Advances. 2026;12(30):eaec8738. Archaeology. Bombyx mori cocoons from Sapalli Tepe, Uzbekistan, directly dated to 1940–1765 cal. BCE, plus the earliest Central Asian mulberry charcoal.
  2. Lee B, Pires E, Pollard AM, McCullagh JSO. Species identification of silks by protein mass spectrometry reveals evidence of wild silk use in antiquity. Scientific Reports. 2022;12(1):4579. Archaeological science. Not every ancient silk implies domesticated Bombyx and a mulberry plantation.

Mulberry leaf pharmacology, for context

  1. Chan EW, Lye PY, Wong SK. Phytochemistry, pharmacology, and clinical trials of Morus alba. Chinese Journal of Natural Medicines. 2016;14(1):17–30. Review.
  2. Kimura T, Nakagawa K, Kubota H, Kojima Y, et al. Food-grade mulberry powder enriched with 1-deoxynojirimycin suppresses the elevation of postprandial blood glucose in humans. Journal of Agricultural and Food Chemistry. 2007;55(14):5869–5874. Human. The source of the “young summer leaves from the top of the branch” finding that contradicts the classical frost-picked instruction.
  3. Kim DS, Kang YM, Jin WY, Sung YY, et al. Antioxidant activities and polyphenol content of Morus alba leaf extracts collected from varying regions. Biomedical Reports. 2014;2(5):675–680. Analytical / in vitro. Growing region changes leaf chemistry too.
  4. Mudra M, Ercan-Fang N, Zhong L, Furne J, Levitt M. Influence of mulberry leaf extract on the blood glucose and breath hydrogen response to ingestion of 75 g sucrose by type 2 diabetic and control subjects. Diabetes Care. 2007;30(5):1272–1274. Human. The modern indication, in a single experiment.

Live PubMed Searches

  1. Silkworms and mulberry latex alkaloids
  2. Silkworm domestication
  3. Sericulture archaeology
  4. Sang ye in traditional Chinese medicine
  5. Mulberry root bark chemistry — the separate drug
  6. Red and white mulberry hybridisation
  7. Mulberry leaf tea and GABA
  8. Mulberry leaf as fodder

Connections

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