Brazil: Study on Cranberry and Blueberry Consumption

A recent study with high credibility of evidence showed that the consumption of cranberry and blueberry compared to placebo reduced fasting blood sugar and glycated hemoglobin levels in diabetes patients. The results, published in the journal Nutrition, Metabolism & Cardiovascular Diseases on February 16, 2022, were significant only in diabetic individuals.

Cranberry and blueberry are rich in polyphenols that are linked to diabetes reduction. Felipe Mendes Delpino, Postgraduate Program in Nursing, Federal University of Pelotas, Pelotas, Brazil, and colleagues aimed to:

• Systematically review the literature on the effects of blueberry and cranberry consumption and type 2 diabetes parameters in individuals with or without type 2 diabetes.
• Quantify these effects by carrying out a meta-analysis.

For this purpose, the researchers performed a systematic review and meta-analysis using articles present in seven databases (PubMed, LILACS, Scielo, Web of Science, Scopus, Cochrane, and Embase), consisting of publications until May 2021. Randomized clinical trials that compared blueberry or cranberry effects on type 2 diabetes parameters, such as fasting blood sugar, glycated hemoglobin, and insulin resistance were included.

Cochrane scale was used to perform the quality of the studies, while the Egger test assessed the publication bias and meta-regression estimated the effect sizes with potential moderator variables. Of the 2034 identified studies, 39 were read in full and 22 were included in the meta-analysis.

Key Findings

• In individuals with diabetes, the consumption of blueberry or cranberry significantly reduced fasting blood glucose [MD: −17.72 mg/dl] and glycated hemoglobin [MD: −0.32], whereas for insulin resistance the effects were null.
• Results were not significant for the general population, except in the sensitivity analysis for fasting blood glucose.

The researchers conclude, "compared to placebo, blueberry or cranberry consumption reduced fasting blood glucose, insulin resistance, and glycated hemoglobin."

Reference

Delpino FM, Figueiredo LM, Gonçalves da Silva T, Flores TR. Effects of blueberry and cranberry on type 2 diabetes parameters in individuals with or without diabetes: A systematic review and meta-analysis of randomized clinical trials. Nutr Metab Cardiovasc Dis. 2022 Feb 17:S0939-4753(22)00083-7. doi: 10.1016/j.numecd.2022.02.004. Epub ahead of print. PMID: 35282984.

Keywords

Nutrition Metabolism & Cardiovascular Diseases, blueberry, cranberry, diabetes, blood sugar, insulin resistance, glycated hemoglobin, fasting blood glucose, berries, polyphenols, Felipe Mendes Delpino