Blueberry, cranberry confer antidiabetic benefits

Blueberries and cranberries may offer benefits to patients with diabetes, with a recent study showing that eating these fruits can produce significant reductions in fasting blood glucose and glycated haemoglobin levels.

Researchers conducted a systematic review and meta-analysis of studies investigating the effects of blueberry and cranberry consumption on diabetes parameters—such as fasting blood glucose, insulin resistance, and glycated haemoglobin—in individuals with or without type 2 diabetes. They searched multiple online databases and identified 2,034 studies.

Of the studies, 39 were read in full and 22 were included in the meta-analysis. Pooled data revealed that for patients with type 2 diabetes, the consumption of blueberry or cranberry led to a marked decrease in fasting blood glucose (mean difference [MD], –17.72 mg/dl, 95 percent confidence interval [CI], –29.62 to –5.82; p=0.03; I², 57 percent) and glycated haemoglobin (MD, –0.32 percent, 95 percent CI, –0.57 to –0.07; p=0.15; I², 39 percent).

On the other hand, the effects on insulin resistance were null.

For the general population, consumption of the berries had no significant effect on any of the diabetes parameters, except in the sensitivity analysis for fasting blood glucose.

The credibility of the evidence is high according to the Cochrane scale.

Blueberries and cranberries are rich in polyphenols—substances that are associated with antidiabetic effects. The two fruits have similar nutritional composition of macronutrients and fibre, although blueberry polyphenol concentrations have been shown to be two times greater. According to previous studies, dietary polyphenols also influence blood glucose and lipid metabolism. [Crit Rev Food Sci Nutr 2019;59:1816-1828]