Mulberry
Berry of the Silk Road — white mulberry's 1-DNJ is a glucosidase blocker, black mulberry's anthocyanins feed the colon.
Mulberry in 1 minute
What does it provide? Anthocyanins (black mulberry is mainly rich in cyanidin-3-glucoside — 0.1–1.5 g/100 g fresh berry), resveratrol (in the peel and leaf, a rare "non-grape" source), quercetin glycosides, and the iminosugar 1-deoxynojirimycin (1-DNJ) present in the leaf of white mulberry (Morus alba) and, to a lesser extent, in the berry — an α-glucosidase inhibitor that reduces postprandial blood-sugar rise (Hu 2013, Asai 2011). Colonic bacteria convert cyanidin-3-glucoside into protocatechuic acid and other small phenolic acids that are anti-inflammatory and vascular-protective (de Ferrars 2014).
How much? Fresh berry 80–150 g/day (frozen is also fine — anthocyanin tolerates freezing well). Dried mulberry (mostly white) 20–30 g/day, sugar-rich, in moderation. Mulberry-leaf tea (1-DNJ content): 1–3 cups/day, with meals or 15 minutes before — Mudra 2007 single-meal post-prandial sucrose challenge in T2D + controls (n≈10) showed reduced post-prandial glycemia.
When to avoid? With insulin or sulfonylurea treatment, DNJ-containing leaf/extract may enhance hypoglycemia (medical consultation), anticoagulant therapy (clinical-dose resveratrol bleeding risk), Moraceae allergy (possible fig cross-reactivity), severe fructose malabsorption (ripe berry is sweet).
The mulberry (Morus) has three main species — white (M. alba), black (M. nigra), and red (M. rubra) — and along the Silk Road it was simultaneously food, medicine, and an economic foundation. White mulberry originated in northern China: finds from the Shang dynasty (c. 16th–11th c. BCE) already show silkworm (Bombyx mori) breeding fed on Morus alba leaves — the 5,000-year-old secret of silk. In Chinese medicine, every part of the white mulberry has a role: leaf (sang ye) as a cooling, glycemia-moderating tea, root bark (sang bai pi) as a cough suppressant, berry (sang shen) as a blood and liver tonic. Black mulberry (M. nigra) originates from the Caucasus and Persia; the ancient Greeks called it "morea," and Hippocrates recommended it as an expectorant.
Emperor Justinian of the Byzantine Empire, around 552 CE, had silkworm eggs smuggled from China — two Nestorian monks carried them in hollow bamboo staffs — and thereby founded Mediterranean silk production, whose base was the mulberry plantation. In Italy, Spain, and the Ottoman-era Balkans (including Hungary), significant mulberry plantations grew; King Matthias' garden in Visegrád allegedly also held black mulberries. Turkish-Balkan cuisine of the 19th century produced the thick mulberry molasses known as pekmez, still an Anatolian breakfast classic. Modern nutritional interest returned in the 2000s, when the 1-DNJ content of white mulberry leaf and the anthocyanin profile of black mulberry were lifted into public awareness by diabetes and metabolic-syndrome research.
Scientific Background
The anthocyanin concentration measured in fresh black mulberry (Morus nigra) berries (mainly cyanidin-3-glucoside and cyanidin-3-rutinoside) ranges from 100–1500 mg/100 g — comparable to blueberry or aronia (Sánchez-Salcedo 2015, Tomás-Barberán 2016). Anthocyanins themselves are poorly absorbed (< 1%), but in the colon Bacteroides, Bifidobacterium, and Lactobacillus species convert them into protocatechuic acid, vanillic acid, caffeic acid, and other small phenolic acids (de Ferrars 2014). These metabolites improve endothelial function (Khan 2014 human RCT) and are anti-inflammatory.
The unique active ingredient of white mulberry is 1-deoxynojirimycin (1-DNJ) — an iminosugar that is a competitive inhibitor of the α-glucosidase enzyme (like the drug acarbose). In Asai 2011's human RCT, a white-mulberry-leaf extract (12 mg 1-DNJ) significantly reduced postprandial glucose and insulin response after a carbohydrate load. In Mudra 2007's single-meal 75 g sucrose challenge (T2D + controls, n≈10), mulberry-leaf extract reduced the post-prandial glycemic and breath-hydrogen response — this was an acute postprandial study, not a long-term HbA1c trial. The berry's 1-DNJ content is significantly lower than the leaf's, but still detectable.
Resveratrol and other stilbenes are most associated with grapes — but Sánchez-Salcedo 2015 also detected 25–50 mg/kg resveratrol in black mulberry peel, placing it in the higher range among temperate fruits. Quercetin glycosides (rutin, isoquercitrin) are anti-inflammatory and capillary-stabilizing. Mulberry's fiber and pectin content (1.7–2.4 g/100 g) is moderate, but together with the whole polyphenol matrix gives an SCFA-promoting prebiotic effect.
Because of the DNJ content of leaf and berry, diabetic patients (especially on insulin or sulfonylurea) should watch for hypoglycemia signs — the effect is small but additive. In healthy, normoglycemic populations, the effect is safe and rather favorable.
- + Yogurt, kefir (live culture): synbiotic breakfast — anthocyanin × lactic acid bacteria, well-documented SCFA synergy.
- + Oatmeal, walnut, almond: classic mulberry muesli, β-glucan + polyphenol synergy.
- + Green or white tea: catechin × anthocyanin antioxidant co-effect.
- + Frozen in smoothie: cold preservation preserves anthocyanins.
- + Flax, chia: + soluble fiber, broader prebiotic profile.
- + Fig (Moraceae group): flavor and botanical synergy.
- Insulin / sulfonylurea + white-mulberry-leaf extract: hypoglycemia risk — medical consultation.
- Anticoagulant therapy + large-dose resveratrol-rich dried peel extract: theoretical bleeding enhancement.
- Iron supplementation in the same meal: polyphenols (tannins) chelate non-heme iron — ≥ 2-hour separation.
- Sugared "mulberry jam" or syrup: glycemic spike, the DNJ benefit is partly lost.
- Prolonged high-heat cooking: > 30% anthocyanin loss.
- Chlorinated tap-water wash with long soaking: polyphenols partly oxidize.
- Insulin- or sulfonylurea-treated diabetes: DNJ-containing leaf/extract carries hypoglycemia risk — frequent glucose monitoring, medical consultation.
- Anticoagulant therapy (warfarin, DOAC): clinical-dose resveratrol supplement to be avoided.
- Moraceae allergy: rare, but cross-reactivity between Morus and Ficus is possible.
- Severe GERD active phase: ripe sweet berry is generally well tolerated, but the acidity may disturb.
- Severe forms of fructose malabsorption: larger portions may cause symptoms.
- Pregnancy / lactation + DNJ extract: evidence lacking — food-amount berry is safe, avoid concentrated extracts.
- Infant (under 1 year): finely chopped, small portion — choking prevention.
- Antibiotic / chemotherapy + high DNJ dose: theoretical interference — food-amount is safe.
References
[1] Asai A et al. Inhibitory effect of mulberry leaf extract on postprandial hyperglycemia in normal and diabetic subjects. J Diabetes Investig 2011;2(4):318–323. Link
[2] Mudra M et al. 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. Link
[3] Hu XQ et al. Hypoglycemic effect of Morus alba L. leaves and its quality control. Mini Rev Med Chem 2013;13(5):717–728.
[4] Sánchez-Salcedo EM et al. Phytochemical evaluation of white (Morus alba L.) and black (Morus nigra L.) mulberry fruits, a starting point for the assessment of their beneficial properties. J Funct Foods 2015;12:399–408.
[5] de Ferrars RM et al. The pharmacokinetics of anthocyanins and their metabolites in humans. Br J Pharmacol 2014;171(13):3268–3282.
[6] Khan N et al. Anthocyanins improve endothelial function: a systematic review of human studies. Mol Nutr Food Res 2014;58(5):951–963.
[7] Tomás-Barberán FA, Selma MV, Espín JC. Interactions of gut microbiota with dietary polyphenols and consequences to human health. Curr Opin Clin Nutr Metab Care 2016;19(6):471–476.
[8] Yang X et al. Mulberry leaf polysaccharides and their potential health benefits. Carbohydr Polym 2017;174:1175–1184.
[9] Monash University. High and Low FODMAP foods — mulberry. Monash FODMAP database. Link