Does mulberry leaf tea help lower blood sugar?
Mulberry leaf tea lowers the blood sugar spike after a meal. With longer use, fasting blood sugar and the long-term marker HbA1c also decrease, especially in people whose blood sugar is already elevated.
Mulberry leaves lower the blood sugar spike after a meal. Many studies combined show that fasting blood sugar drops by an average of 0.47 mmol/L, and the long-term marker (HbA1c) by an average of 2.92 mmol/mol. A separate analysis of thirteen studies confirms that blood sugar stays noticeably lower in the first 90 minutes after a meal: at 30 minutes an average of 1.04 mmol/L less, and at 60 minutes 0.87 mmol/L less. These are small but measurable reductions.
The effect is strongest in people who already have an elevated fasting blood sugar (above 6.1 mmol/L) and when mulberry leaves are used for at least 8 weeks. A more recent analysis of 15 studies involving over 1,200 participants adds that mulberry leaf extract also improves cholesterol, LDL, triglycerides, and markers of inflammation. Notably, that analysis found the greatest effect at doses below 500 mg per day.
Not all findings point clearly in the same direction. One analysis did find an effect on the post-meal blood sugar spike, but found no clear effect on fasting blood sugar, HbA1c, or blood fats. That conflicting result most likely reflects differences in how studies were run, the products used, and when measurements were taken.
Most of the smaller studies used a combination product or extract, not tea exclusively. Two studies using a combination of mulberry leaves and watercress as a tea did show a clear reduction in the post-meal blood sugar spike and in blood sugar fluctuations throughout the day among people with borderline diabetes, with no adverse effects on the liver, kidneys, or blood sugar falling too low. A study using fortified milk (funded by Nestlé) found an early reduction of 25%, but no effect over three hours in total.
If you have diabetes or use blood-sugar-lowering medication, speak with your doctor before using mulberry leaves, as the effects may interact.
This answer draws on four combined analyses of multiple studies, the largest of which includes over 1,200 participants, and on five individual studies. The analyses covering fasting blood sugar and HbA1c are the most robustly supported. The studies specifically on tea are small (30 to 31 participants) and partly used combination products, meaning the effect cannot be attributed entirely to mulberry leaves alone. One study was funded by Nestlé. Two separate combined analyses partly contradict each other on effects beyond the post-meal spike, which limits certainty.