Anthocyanins

Anthocyanins belong to the flavonoid family. They give blueberries, blackcurrants, blackberries, cherries, red cabbage, aubergines and black grapes their colour, from red to deep blue depending on the acidity of the environment.

This sensitivity to pH is visible in the kitchen: red cabbage turns blue-purple in a neutral medium and regains its red colour with a splash of vinegar. The same phenomenon explains why the colour of a red fruit preparation changes depending on the ingredients combined with it.

Their value goes beyond the antioxidant capacity measured in a test tube. This is the useful nuance: they are poorly absorbed and stay in the blood only briefly, which long made their role doubtful. Recent work points to two sounder avenues: an effect on endothelial function, and therefore on the flexibility of blood vessels, and an action of their metabolites produced by the gut microbiome, which may be the real players.

On the practical side: they are water-soluble and sensitive to heat, so they are partly lost when cooking in water. Frozen red fruit retains most of them. And the usual rule applies: variety among coloured plant foods matters more than seeking out the most « concentrated » fruit.

The anthocyanins in berries are of particular interest for the brain: they are among the few polyphenols whose metabolites appear to reach brain tissue, and several studies link them to better memory performance and slower cognitive decline. This is what earns blueberries and dark berries their reputation as « brain foods », a serious lead, but not yet a certainty.

Their relationship with the gut microbiome works both ways: gut bacteria convert anthocyanins into active metabolites, and these compounds in turn feed the gut flora, with a prebiotic effect. The benefit therefore depends partly on the state of the gut. In practice, a simple visual guide is enough: the more intense and darker the colour, the higher the content, and frozen berries retain it very well.