Mulberry-extract improves glucose tolerance and decreases insulin concentrations in normoglycaemic adults: Results of a randomised double-blind placebo-controlled study

PLoS One. 2017 Feb 22;12(2):e0172239. doi: 10.1371/journal.pone.0172239. eCollection 2017.

Abstract

Background: High sugar and refined carbohydrate intake is associated with weight gain, increased incidence of diabetes and is linked with increased cardiovascular mortality. Reducing the health impact of poor quality carbohydrate intake is a public health priority. Reducose, a proprietary mulberry leaf extract (ME), may reduce blood glucose responses following dietary carbohydrate intake by reducing absorption of glucose from the gut.

Methods: A double-blind, randomised, repeat measure, phase 2 crossover design was used to study the glycaemic and insulinaemic response to one reference product and three test products at the Functional Food Centre, Oxford Brooks University, UK. Participants; 37 adults aged 19-59 years with a BMI ≥ 20kg/m2 and ≤ 30kg/m2. The objective was to determine the effect of three doses of mulberry-extract (Reducose) versus placebo on blood glucose and insulin responses when co-administered with 50g maltodextrin in normoglycaemic healthy adults. We also report the gastrointestinal tolerability of the mulberry extract.

Results: Thirty-seven participants completed the study: The difference in the positive Incremental Area Under the Curve (pIAUC) (glucose (mmol / L x h)) for half, normal and double dose ME compared with placebo was -6.1% (-18.2%, 5.9%; p = 0.316), -14.0% (-26.0%, -2.0%; p = 0.022) and -22.0% (-33.9%, -10.0%; p<0.001) respectively. The difference in the pIAUC (insulin (mIU / L x h)) for half, normal and double dose ME compared with placebo was -9.7% (-25.8%, 6.3%; p = 0.234), -23.8% (-39.9%, -7.8%; p = 0.004) and -24.7% (-40.8%, -8.6%; p = 0.003) respectively. There were no statistically significant differences between any of the 4 groups in the odds of experiencing one or more gastrointestinal symptoms (nausea, abdominal cramping, distension or flatulence).

Conclusions: Mulberry leaf extract significantly reduces total blood glucose rise after ingestion of maltodextrin over 120 minutes. The pattern of effect demonstrates a classical dose response curve with significant effects over placebo. Importantly, total insulin rises were also significantly suppressed over the same time-period. There were no statistically significant differences between any of the treatment groups (including placebo) in the odds of experiencing one or more gastrointestinal symptoms. Mulberry extract may have multiple modes of action and further studies are necessary to evaluate ME as a potential target for the prevention of type 2 diabetes and the regulation of dysglycaemia.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Blood Glucose / drug effects*
  • Blood Glucose / metabolism
  • Cross-Over Studies
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Female
  • Glucose Tolerance Test
  • Humans
  • Insulin / blood*
  • Male
  • Middle Aged
  • Morus*
  • Plant Extracts / pharmacology*
  • Young Adult

Substances

  • Blood Glucose
  • Insulin
  • Plant Extracts

Grants and funding

The work has been funded by a Technology Strategy Board/Innovate UK grant (101726). CB is supported in part by the Southampton National Institute for Health Research Biomedical Research Centre. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.