Can Mulberry Leaf Tea Tame Blood Sugar Spikes?

What Was Studied and Why It Matters

Every time you eat, your blood sugar rises. For people with diabetes — and even for healthy individuals — sharp spikes in blood sugar after meals (called postprandial hyperglycemia) are linked to a higher risk of heart disease and worsening diabetes over time. Researchers in Japan wanted to know whether a traditional herbal tea made from mulberry leaves and water chestnut could help flatten those spikes naturally.

The tea, known as Kanzaki MW tea, is rich in plant compounds called polyphenols and a natural substance called 1-deoxynojirimycin (DNJ), which is known to slow how quickly the body absorbs sugar from food. While individual cups of mulberry tea have shown promise, this 2025 study published in Nutrients was one of the first to test two full weeks of daily use in a rigorous clinical setting.

How the Study Was Done

Thirty-one adults took part in this randomized, double-blind, placebo-controlled crossover trial — considered one of the gold standards in medical research. Participants drank either the real MW tea or a look-alike placebo before meals for two weeks, then switched groups after a one-week break. Neither the participants nor the researchers knew who was drinking what during each phase.

Blood sugar was tracked continuously using a continuous glucose monitor (CGM) — a small sensor worn on the body that measures glucose levels every 15 minutes around the clock. On the first day of each two-week period, participants also ate a standardized meal so researchers could measure the exact glucose response over three hours.

What the Researchers Found

• Less daily glucose variability: People drinking MW tea had significantly more stable blood sugar throughout the day compared to the placebo group — a meaningful benefit for long-term health.
• Smaller post-meal spikes: Blood sugar levels in the first hour after a standardized meal were significantly lower during the tea period.
• Improved glycemic control marker: Levels of a compound called 1,5-anhydroglucitol (1,5-AG) — a reliable indicator of overall glucose control — rose significantly during the tea period, suggesting the body was managing sugar more effectively overall.
• No safety concerns: There were no meaningful differences in dangerous low blood sugar episodes, liver function, kidney function, or inflammation markers between the two groups.

What This Means for Real Patients

For people managing diabetes or trying to prevent it, this study suggests that drinking MW tea before meals could be a safe and practical way to reduce blood sugar spikes — without the risk of hypoglycemia (dangerously low blood sugar) that some medications carry.

That said, this was a small study of 31 people over just two weeks. Larger, longer trials are needed before MW tea can be widely recommended as a treatment. It should be viewed as a potential complement to — not a replacement for — your existing diabetes management plan, including medication, diet, and monitoring.

Speaking of monitoring: accurate, consistent blood sugar tracking is the foundation of good diabetes management. Whether you use a CGM or traditional fingerstick testing, having reliable supplies matters. MDS Diabetes offers a wide range of glucose monitoring supplies to help you stay on top of your numbers every day.

Bottom Line

Drinking mulberry leaf and water chestnut tea before meals for two weeks significantly reduced post-meal blood sugar spikes and daily glucose swings in a well-designed clinical trial — with no notable side effects. While more research is needed, MW tea shows real promise as a natural, safe addition to a diabetes-friendly lifestyle.