A promise is circulating widely online: a diet rich in four food categories would significantly reduce the risk of dementia. Articles summarize the work of a neuroscientist and his team. The idea reassures many relatives of elderly people, but the scientific reality is a little different.
What are these key foods?
Behind these catchy titles lies the
Mediterranean dietrich in plants, whole grains and olive oil, with little red meat and ultra-processed foods.
Several cohorts, from the French Trois-Cités study led by Cécilia Féart to the British analysis by Oliver M. Shannon, link strong adherence to this diet to a lower risk of dementia. The World Health Organization (WHO) guidelines speak of a possible effect, inserted into a prevention strategy.
Mediterranean diet and risk of dementia: what studies show
In the Bordeaux cohort of the Trois-Cités study, 1307 people aged around 74, without dementia at baseline, were followed for twelve years.
Those who obtained the highest scores for adherence to the Mediterranean diet had a reduced risk of dementia by approximately
42% to 66% according to the criteria, especially for Alzheimer’s disease after several years.
Another study, published in 2023 in the journal BMC Medicine by Oliver M. Shannon, followed just over 60,000 Britons over the age of 60 for around nine years.
People who most closely followed a Mediterranean diet had a relative risk of dementia around
23% lower. The absolute risk even increases from 1.73% to 1.18%, including among those with an unfavorable genetic profile.
Four families of foods at the heart of the Mediterranean diet
The formula of ‘four foods’ comes from a simplification of the work of researcher Alba Tor-Roca. She followed 840 seniors from Bordeaux and Dijon for twelve years.
His team analyzed blood biomarkers and showed that a diet rich in plants – fruits, vegetables, whole grains and legumes – combined with olive oil and fish corresponds to a high Mediterranean score, linked to around 10% less probability of cognitive decline.
This food base acts on several fronts:
-
Plant fibers and polyphenols nourish the microbiota and limit inflammation;
- Whole grains and legumes stabilize blood sugar levels;
- Olive oil and fish provide artery-friendly fats.
By protecting the heart and vessels, this diet also reduces key risk factors for dementia such as hypertension or diabetes, which is suggested by the French and British cohorts.
No miracle diet for dementia, but a real asset
Despite these signals, the World Health Organization guidelines reiterate that clinical trials have not shown a clear decline in the incidence of dementia in people assigned to a Mediterranean diet. Experts see it as one lever among others, to be associated with physical activity and blood pressure control.
In practice, filling the plate more often with fruits, vegetables, whole grains and olive oil can help the brain age well, but does not replace medical monitoring or management of other risk factors.