https://www.greenmedinfo.com/blog/berries-top-anti-diabetes-food?

Berries aren't called superfoods for nothing. A review covering 336 scientific articles on these fruits has shown that berry consumption can go a long way in preventing and managing Type 2 diabetes and its complications.
From the hunter-gatherers of ancient times to modern humans, berries hold incredible health benefits that only get further proven and respected over time. Coming in different varieties and forms like raw, frozen and dried, these compact and versatile fruits can be easily incorporated into your diet year round.
Berries are chock-full of antioxidants, which are substances that help prevent the oxidation associated with inflammation, aging and the development of diseases such as heart disease and cancer.[i]
They are deemed "promising functional fruits" for their distinct therapeutic contents of anthocyanins, flavonoids, flavanols, alkaloids, organic acids and more -- polyphenols that may be beneficial for oxidative stress, obesity, high blood pressure and diabetes.[ii]
In studies, polyphenols along with other berry components such as fiber and micronutrients have been linked with better cardiovascular health.[iii] Each type of berry has its specific "superpower," from cranberry's efficacy in treating and preventing urinary tract infections to strawberry's outstanding vitamin C content to black currant's support for brain power and efficacy against rheumatoid arthritis.
Polyphenol-Rich Berries Deter Diabetes and Its Complications
An August 2020 review discussed how consuming berries can prevent diabetes and its complications.[iv] Analyzing the differences in glucose and insulin levels after food intake in diabetic subjects, the reviewed studies found that consuming berries can be a reliable method to prevent and manage hyperglycemic and hyperlipidemic states.
The researchers examined berry consumption and the management of Type 2 diabetes by searching various scientific databases using keywords such as "berry consumption and diabetes," "berries and high-glycemic diets" and individual berry names. This yielded 336 articles deemed relevant for the review.
Various berries have been probed for their potential diabetes benefits, including blueberries, bilberries, cranberries, raspberries, mulberries, lingonberries, blackberries, strawberries, goji berries, acai berries, chokeberries, black currants and maqui berries. The review showed berries' various mechanisms of action against diabetes, including the following:
Anthocyanins promoted glucose uptake and metabolism as well as inhibited weight gain and pro-inflammatory responses
Berry intake led to improvements in insulin sensitivity and lowering glucose
Berry consumption favorably altered gut microflora, thus assisting in diabetes management
The primary potential health-promoting bioactive compounds in berries include the following:
Glycosides, Glucosides, Catechins, Epicatechins, Quercetin, Myricetin, Flavanolds, Flavonols
Caffeic acids, Phenolic acids, Polysaccharides