How healthy are blueberries and other red/blue fruits for your brain?
Eating blueberries daily or taking them as a supplement appears worthwhile if you are middle-aged or older with mild memory complaints or insulin resistance. If dementia has already been diagnosed, it is unlikely to offer much benefit.
Blueberries and other red/blue fruits are good for your brain, at least if you are middle-aged or older and dealing with mild memory complaints. That picture emerges from multiple human studies and is by now reasonably consistent. For example, daily blueberry supplementation in 50-65-year-olds with insulin resistance and memory complaints improved word retrieval and the ability to resist memory interference. Participants also experienced less forgetfulness in daily life, and their elevated insulin levels normalised, suggesting that metabolism plays a role in the protective effect.1
A review of 11 randomised trials confirms this. Berries in all kinds of forms, such as frozen fruit, concentrate, juice, capsules or extract, had a beneficial effect on memory, attention, processing speed, executive functions and resting cerebral blood flow. However, the participants had no or only mild complaints, not an established diagnosis of dementia.2
Studies using blueberry supplementation or grape juice in people with mild cognitive complaints showed improved memory scores. The effects are small and the total number of studies is limited, but the results point in the same direction.3,4
Why it works is biologically plausible. Studies in animals and in the laboratory show that polyphenols, the coloured plant compounds in berries, reduce oxidative stress and inflammation in the brain, improve signal transmission between nerve cells and may stimulate the formation of new brain cells in the memory centre. Whether this provides direct protection against Alzheimer's or Parkinson's disease in humans has not yet been demonstrated.5,6,7
A few caveats: in people with an established diagnosis of dementia, berries appear to offer little benefit. It is also notable that blueberries and fish oil taken together in one study produced no improvement, whereas each did so when taken separately. This calls for further research. A large three-year study with 604 participants is still ongoing, but those results are not yet available.8
The claims are based on one randomised trial (PMID 35458181), a review of 11 randomised trials (PMID 35217779), smaller human studies (PMID 19640963, 33099465), a design article for a large ongoing study (PMID 33434704) and review articles consisting primarily of animal and laboratory data (PMID 29141966, 18211020, 11976192). The total number of participants across the human studies is estimated at 600 to 900 persons.