The study – which was part of A Healthy Diet for a Healthy Life, a European Joint Programming Initiative that brings together 17 countries to fund research to minimise diet-related chronic diseases – was carried out over 12 years and involved 840 people aged over 65 years from the French regions of Bordeaux and Dijon.

It provides new evidence for a better understanding of the biological mechanisms related to the impact of the diet on cognitive health in the ageing population.

First author Alba Tor-Roca, a researcher at the CIBER on Frailty and Healthy Ageing (CIBERFES), said: “We found that adherence to Mediterranean diet assessed by a panel of dietary biomarkers is inversely associated with long-term cognitive decline in older people.

“These results support the use of these indicators in long-term follow-up assessments to observe the health benefits associated with the Mediterranean diet or other dietary patterns and, therefore, guide personalised counselling at older ages.”

‘Inconclusive’ evidence on link between Mediterranean diet and cognitive performance

CIBERFES researchers have previously highlighted increasing evidence that the regular consumption of polyphenols can contribute to healthy ageing, particularly if combined with a healthy lifestyle and diet, such as the Mediterranean one.

However, evidence on the link between the Mediterranean diet and age-related cognitive decline has been inconclusive to date, in large part because of irregularities in self-reported dietary assessment.

The aim of this study, which was published in Molecular Nutrition and Food Research, was to develop a Mediterranean diet metabolomic score (MDMS) and investigate its association with cognitive decline in community-dwelling older adults.

Professor Cristina Andrés-Lacueva, head of the CIBERFES group, said: “Within the framework of the study, a dietary metabolomic index has been designed – based on biomarkers obtained from the participants’ serum – on the food groups that form part of the Mediterranean diet. Once this index is known, its association with cognitive impairment is evaluated.”

Biomarkers measured included baseline levels of saturated and unsaturated fatty acids; gut microbiota-derived polyphenol metabolites; and other phytochemicals in serum that reflect individual bioavailability.

Some of these have not only been recognised as marks of exposure to the main food groups of the Mediterranean diet but are also believed to be responsible for its health benefits.

Biomarkers for measuring Mediterranean diet benefits

The metabolome or set of metabolites — related to food and derived from gut microbiota activity — was studied through a large-scale quantitative metabolomic analysis from the serum of the participants without dementia, from the beginning of the study.

Cognitive impairment among participants, 65% of whom were women, was assessed by five neuropsychological tests over 12 years.

The findings reveal a protective association between the score of the Mediterranean diet based on serum biomarkers and cognitive decline in older people.

Mercè Pallàs, professor at the University of Barcelona Neurosciences Institute, said: “The use of dietary pattern indices based on food-intake biomarkers is a step forward towards the use of more accurate and objective dietary assessment methodologies that take into account important factors such as bioavailability.”

The study was carried out in collaboration with teams from other departments of the University of Barcelona; researchers from the University of Bordeaux and the INRAE centre at Clermont-Ferrand University (France), King’s College London (UK), the University of Amsterdam (the Netherlands), and the Parcelsus Medical University in Salzburg (Austria) also participated.

Funding was obtained through the International Joint Programming Actions PCIN-2015-229, the European Regional Development Funds, and from the former Ministry of Economy, Industry and Competitiveness via the A Healthy Diet for a Healthy Life initiative.