Benefits
Smaller blood sugar rise after a starch or sugar load
In two placebo-controlled crossover tests in healthy adults, the extract lowered the 2-hour glucose response, the main outcome, by 14% at 250 mg and 22% at 500 mg with 50 g maltodextrin (125 mg did not differ), and by 42% when 250 mg was stirred into a 75 g sucrose drink. Each was a single-meal test, one funded by the maker.
Smaller blood sugar rise after a full meal
Before a white bread and egg meal, 200, 225 and 250 mg lowered the 2-hour glucose response by 30 to 33% versus placebo in 37 healthy adults, in a maker-funded test. In an open-label Nestlé test in 30 healthy adults, 250 mg lowered the 2-hour response to a rice and chicken meal by 26% taken before it and 34% stirred into it, versus water.
Lower insulin response after carbohydrate
In the same single-meal tests, the 2-hour insulin response was about 24% lower than placebo at 250 and 500 mg with maltodextrin, 40% lower with sucrose, and 31 to 38% lower with a bread meal. In the bread meal test, insulin at 3 hours was higher than placebo after 225 mg, in the late part of the curve.
Post-meal glucose with a sprinkled blend at breakfast
In 30 adults with type 2 diabetes, a 2 g blend containing 250 mg of the extract with fiber, vitamin D and chromium lowered the 3-hour glucose response by 15% and the 1-hour response by 20% versus the same blend without the extract. Insulin was lower only in the first hour. The test was exploratory, a single meal and funded by Nestlé.
Slower digestion of sucrose in the gut
In 18 adults, a labeled-sucrose breath test was repeated with 750 mg of the extract taken just before the sucrose; the labeled carbon dioxide recovered over 4 hours fell by more than half versus the baseline test, a sign that less sucrose was split and absorbed. The methods describe no placebo; the maker supplied the extract and the authors declared no commercial conflicts.
Mechanism of action
Blocking the enzymes that split sugars and starch
DNJ resembles glucose and competes for the brush border enzymes sucrase, maltase and isomaltase. In lab tests on human small-intestine samples, a mulberry leaf extract (a different product, 0.24% DNJ) inhibited sucrase by 96%, maltase by 95% and isomaltase by 99%, and the inhibition was competitive in rat tissue.
Less sucrose digested, measured in people
A labeled-sucrose breath test showed the same effect in the body: 750 mg of the extract more than halved the labeled carbon dioxide that appears in breath once sucrose is split and absorbed. Slower splitting means glucose enters the blood more gradually, which fits the lower glucose peaks seen in the meal tests.
Insulin and gut hormones
With less glucose absorbed early, less insulin is released. In the breakfast blend test, the early gut hormone GIP was lower with the extract, while GLP-1 and stomach emptying did not differ. In lab work, the extract raised glucose-stimulated insulin release from rat insulin cells and lowered fasting glucose in diabetic rats; this is animal and cell work only.
Clinical trials
Double-blind, randomized, placebo-controlled four-period crossover dose test at Oxford Brookes University; capsules of 125, 250 or 500 mg Reducose (5% DNJ) or microcrystalline cellulose placebo taken with 50 g maltodextrin. Primary outcome: 2-hour glucose response (positive iAUC). Registered ISRCTN14597438 on 21 April 2015, the day before the first participant was recruited, with a protocol published in 2015. Funded by a Technology Strategy Board/Innovate UK grant; one author was chief operating officer of Phynova, which did not fund the study (Lown et al. 2017, PLoS One)
40 healthy adults aged 19 to 59 with normal blood sugar and BMI 20 to 30 were randomized; 37 completed all four visits (one found the study day too long and two could not finish before the study closed).
Versus placebo, the glucose response was 6.1% lower at 125 mg (p = 0.316, not significant), 14.0% lower at 250 mg (p = 0.022) and 22.0% lower at 500 mg (p < 0.001). The insulin response was 9.7% lower at 125 mg (not significant) and about 24% lower at 250 and 500 mg. The odds of nausea, cramping, distension or flatulence did not differ between any of the four treatments.
Double-blind, randomized, placebo-controlled crossover trial: 250 mg Reducose dissolved in a 75 g sucrose drink versus the sucrose drink alone. Funded by Phynova; one author is a Phynova employee who helped design the study and draft the paper. Retrospectively registered (ISRCTN99601810); a 2021 correction changed one reference only (Thondre et al. 2021, Nutr Metab (Lond))
38 healthy adults aged 20 to 58 enrolled; 37 completed and 36 had complete data.
Versus sucrose alone, the 2-hour glucose iAUC was 42% lower (p = 0.001) and the insulin iAUC 40% lower (p < 0.001); peak glucose was 40% lower and peak insulin 41% lower, while the time to the glucose peak did not change. No adverse events were reported.
Double-blind, randomized, placebo-controlled four-period crossover trial: capsules of 200, 225 or 250 mg Reducose (5% DNJ) or placebo taken with water 10 minutes before 150 g white bread with 50 g egg mayonnaise filling (68.7 g carbohydrate). Primary outcome: 2-hour glucose iAUC. Retrospectively registered (ISRCTN18212231). Funded by Phynova Group Limited, which supplied the capsules and helped conceive and design the study; two authors are Phynova employees who drafted the paper (Thondre et al. 2024, Nutrients)
43 healthy adults aged 18 to 56 recruited; 37 completed all four visits (four withdrew and two were excluded, one for not following study procedures and one as ineligible).
All three doses lowered the 2-hour glucose iAUC versus placebo, by 30% (p = 0.003), 33% (p = 0.001) and 32% (p = 0.002), and the insulin iAUC by 31%, 34% and 38%; the doses did not differ from each other. At 3 hours, plasma insulin was higher than placebo after 225 mg. No adverse events were reported.
Randomized, open-label crossover study (the second of two studies in the paper): 250 mg Reducose (12.5 mg DNJ) in 200 mL water 5 minutes before a 510 kcal meal, or stirred into it, versus 200 mL water; glucose by continuous monitor. Primary outcome: 2-hour glucose iAUC. Registered NCT05112133, where the registry lists 24 enrolled and the 3-hour glucose iAUC as the primary outcome; the registry entry was first submitted on 30 September 2021, after the study ran from January to February 2020, so it was registered retrospectively. All authors were Nestlé Research employees; no external funding (Gheldof et al. 2022, Nutrients)
30 healthy adults (11 women), average age 31, BMI 20 to 29.9 (average 22.9); all 30 were analyzed.
Versus water, the 2-hour glucose iAUC was 26% lower when the extract was taken before the meal (p = 0.002) and 34% lower when stirred into it (p < 0.001); stirring it in gave a 10% lower response than taking it before (p = 0.050). Insulin was not measured.
Randomized, double-blind, controlled exploratory crossover trial at two centers (USA, Singapore): a 2 g blend with 250 mg Reducose (12.5 mg DNJ, produced by Phynova), fiber, vitamin D3 and chromium versus the same blend without the extract, sprinkled on a 350 kcal breakfast with 55.4 g carbohydrate. Primary exploratory endpoint: 3-hour glucose iAUC. Registered NCT04877366 before enrollment began. Funded by Nestlé Health Science, which employed several authors; no Phynova authors (Mohamed et al. 2023, Diabetes Ther)
30 adults of Asian origin with type 2 diabetes (mean age 59, HbA1c 7.1%) enrolled; 29 completed all treatment sequences (one withdrew consent).
Versus the blend without extract, glucose iAUC was 20%, 17% and 15% lower at 1, 2 and 3 hours, and peak glucose 0.8 mmol/L lower. Insulin iAUC was 24% lower at 1 hour only. GLP-1 and stomach emptying did not differ, while GIP was lower. One person reported fatigue after the extract blend; there were no serious adverse events.
Randomized, double-blind, controlled crossover trial: a serving with 750 mg Reducose 1% DNJ grade, whey protein with 120 mg tryptophan, zinc, magnesium, vitamins B3 and B6 versus 4 g wheat gluten hydrolysate, with the evening meal for 14 days each, 28-day washout. Primary outcomes: actigraphy sleep onset latency and sleep efficiency. Registered NCT05372900 before enrollment began. Funded by Nestlé, which employed most authors (Soon et al. 2025, Eur J Nutr)
43 adults aged 25 to 50 with self-reported difficulty falling asleep enrolled; 42 analyzed (one withdrew after randomization, before starting any intervention).
Sleep onset latency was 3.8 minutes shorter on the blend (p = 0.026), and the evening meal 1-hour glucose iAUC was 21% lower (p < 0.001) with a 16% lower glucose peak. Because the blend also held tryptophan and other nutrients and the control was a different protein, neither result can be credited to the extract alone.
Breath test development study (the second Glasgow experiment): the methods describe a baseline breath test with 13C-labeled sucrose alone, then a repeat test with 750 mg Reducose taken about 1 minute before the labeled sucrose, at least 3 days apart, with breath sampled every 15 minutes for 8 hours and recovery compared over 4 hours. A results table calls it a single-blinded, randomized crossover with placebo, but the methods describe no placebo or randomization. Reducose was supplied by Phynova; the authors declared no commercial conflicts (Schillinger et al. 2022, Front Med (Lausanne))
18 adults (9 men, 9 women) in Glasgow, UK, average age 25; the results table lists 17 with data for the Reducose test.
Reducose cut 4-hour recovery of labeled carbon dioxide in breath by more than 50% versus the baseline test with sucrose alone, consistent with blocked sucrose digestion. No blood tests or symptom outcomes were reported for this experiment.