Supplement analysis backed by scientific evidence · PT

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Moderate evidenceHeart & metabolic

Mulberry Leaf

Mulberry leaf extract contains 1-deoxynojirimycin (DNJ), a genuine alpha-glucosidase inhibitor that blunts post-meal blood glucose spikes in controlled trials. The effect is real and mechanistically clear, but it is a meal-timing tool for postprandial glucose, not a treatment for diabetes.

What the science says

  • Blunts post-meal glucose and insulin spikes Moderate evidence

    A double-blind randomized crossover trial of a standardized mulberry leaf extract (Reducose) found dose-dependent reductions in post-meal glucose and insulin after a complex meal, with meaningful effects from 250 mg and clear responses at 500-1,000 mg taken with the meal. The mechanism is the same as prescription acarbose — DNJ competitively inhibits intestinal alpha-glucosidase, slowing starch and sucrose digestion. The extract must be taken with or just before the carbohydrate to work.

  • Small but consistent effects on fasting glucose and HbA1c in meta-analysis Moderate evidence

    A systematic review and meta-analysis of mulberry leaf and mulberry leaf extract on glycemic traits pooled randomized trials and found reductions in postprandial glucose along with modest improvements in fasting glucose and HbA1c. Effect sizes on HbA1c are small (typically a few tenths of a percentage point), trials are short (4-12 weeks), and extract standardization varies widely — so this is a supportive adjunct, not a substitute for glucose-lowering medication.

  • Cardiometabolic claims beyond glucose are weaker Limited evidence

    A meta-analysis of mulberry consumption on cardiometabolic risk factors found some improvement in lipid measures, but effects on blood pressure and body weight were inconsistent and driven by few small trials. Claims that mulberry leaf is a weight-loss agent or a "carb blocker" that lets you eat freely are not supported — the calorie sparing from partial starch inhibition is modest.

Dosage & safety

Studied doseTrials of standardized extract use 250-1,000 mg taken immediately before a carbohydrate-containing meal, with 250 mg (delivering roughly 5 mg DNJ) as the common minimum effective dose and 500-1,000 mg for larger effects. Whole leaf powder or tea is dosed at 3-12 g/day in Asian trials. Look for DNJ standardization on the label — unstandardized leaf powder can contain a fraction of the DNJ in a concentrated extract. Timing is not optional: taken between meals it does nothing.
SafetySide effects mirror acarbose and come from undigested carbohydrate fermenting in the colon: bloating, flatulence, abdominal cramping and loose stools, most common at higher doses and with high-carbohydrate meals. Starting low and titrating reduces this. Real interaction risk with insulin and sulfonylureas — additive glucose lowering can cause hypoglycemia, and note that if hypoglycemia occurs while on an alpha-glucosidase inhibitor, table sugar works poorly and glucose tablets should be used instead. Avoid combining with prescription acarbose or miglitol. Insufficient data in pregnancy and breastfeeding. Mulberry leaf is a food in several Asian cuisines with a long safety record at culinary doses.

Scientific references

Where to buy

Swanson Vitamins, Mulberry Leaf Extract, 500 mg, 60 Capsules

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