Anthocyanins, the red, purple, and blue pigments found in fruits, vegetables, and tubers, can lower the risk of diabetes by influencing inflammation, gut microbiota, and energy metabolism.

The favourable effect of anthocyanins on type 2 diabetes is amplified if the anthocyanin is acylated, which means that an acyl group is added to the anthocyanin's sugar moieties, according to a new review study evaluating the research findings in the area.

A great amount of acylated anthocyanins can be found in purple potatoes, purple sweet potatoes, radishes, purple carrots and red cabbages, whereas bilberries and mulberries contain mostly nonacylated anthocyanins.

Acylated anthocyanins are poorly absorbed in digestion, but they have probiotic properties and reduce the risk of diabetes more efficiently than nonacylated anthocyanins.

"The studies have shown that, in addition to changing physical and chemical properties, the acylation affects how the anthocyanins are absorbed and metabolised," said Postdoctoral Researcher Kang Chen at the Food Sciences Unit, University of Turku, Finland.

The acylated anthocyanins are more effective antioxidants than the nonacylated anthocyanins, and they can also improve the intestinal barrier that enables the absorption of necessary nutrients.

Furthermore, the acylated anthocyanins maintain gut microbiota homeostasis, suppress pro-inflammatory pathways, and modulate glucose and lipid metabolisms.

"The plant's genotype defines what kind of anthocyanins they produce. In general, purple vegetables contain many acylated anthocyanins. Also, purple potatoes, especially the Finnish variety called 'Synkea Sakari', are abundant in acylated anthocyanins," said Chen.

Acylated anthocyanins travel through our bodies from the upper gastrointestinal tract to the colon where they are metabolised by the gut microbiota.

Glucose transporters are involved in anthocyanin absorption, but different glucose transporters are responsible for the absorption of acylated and nonacylated anthocyanins. The acylated and nonacylated anthocyanins also have different impacts on the enzymes involved in metabolism.

"The latest research has shown that the acylated and nonacylated anthocyanins can impact type 2 diabetes in different ways," Chen summarises.