Wild blueberries (bilberries)

Wild blueberries (bilberries) are small, dark berries coloured right through. Use them fresh or frozen in porridge or yoghurt. Season: July to September.

What are wild blueberries? The dark difference

Most people today reach for the big, shiny 500 g punnet of cultivated blueberries at the supermarket without a second thought – fitness marketing has made them very popular. Bite into a large cultivated blueberry and you'll see: the inside is pale green, soft and watery-sweet. Wild European blueberries, or bilberries (Vaccinium myrtillus), are different. They're tiny, slightly tart berries that grow on heaths and moorland across Europe. Bite into one and it bursts with deep purple juice that stains your fingertips for days. These deep pigments are exactly why wild blueberries get so much attention in research.

What's in them compared with cultivated blueberries

Wild blueberries grow under tougher northern conditions, and that shows in what they contain:

• Anthocyanins (purple pigments): wild blueberries contain many times more of these pigments than large supermarket blueberries, because the colour runs right through the flesh.
• Pterostilbene: a plant compound related to resveratrol (known from red wine). Because it is fat-soluble, researchers are looking at whether it can reach the brain.

What studies have looked at

Brain and memory: BDNF

For a long time it was thought that the adult brain no longer forms new nerve cells. Today, neuroscience looks closely at proteins such as BDNF (brain-derived neurotrophic factor), which is involved in the growth of nerve cells and new connections between them. Researchers are studying whether compounds from concentrated wild blueberries affect BDNF levels. One study reported that people aged 60 and over did better in word and memory tests two hours after a concentrated blueberry drink. These are early results, not a recommendation for treatment.

Eyes and night vision

The anthocyanins in wild blueberries are often linked with the tiny blood vessels in the eye. A well-known story says that British pilots in the Second World War ate bilberry jam before night flights to see better in the dark. It's a story, not a study result – what effect bilberries have on the eyes is still being researched.

Milk or no milk?

Some studies suggest that milk proteins (casein) can bind polyphenols from berries, which could reduce how many are absorbed. If you want to play it safe, blend frozen wild blueberries with water, avocado and raw cacao rather than cow's milk.