A study published in the journal Alzheimer’s Research & Treatment describes that the Mediterranean and MIND diets could effectively preserve episodic and visuospatial working memory in middle age.
Study: Dietary patterns and cognitive performance in a UK twin women’s registry (TwinsUK). Image credit: DiViArt / Shutterstock
Record
Age-related cognitive decline is a public health concern as it can affect morbidity and mortality. Although most people experience cognitive decline in middle age, the rate of cognitive decline can vary greatly among individuals depending on their cardiovascular health and lifestyle behaviors. A faster-than-usual rate of cognitive decline with age may be a risk factor for Alzheimer’s disease.
Nutrient-rich dietary patterns, such as the Mediterranean (MED) and the Mediterranean Dietary Approach to Stop Hypertension Intervention for Neurodegenerative Delay (MIND) diets, are known to have neuroprotective and cognitive abilities. In this context, evidence suggests that the MED diet can improve cognitive functions by positively affecting the gut microbiota.
In this study, scientists investigated the impact of the MED and MIND diets on cognitive function and 10-year change in cognitive performance in cognitively healthy female twins.
Study design
The study analyzed data obtained from the UK Adult Twin Registry that enrolled healthy female twins between 1992 and 2004. A total of 509 twins who had complete baseline data on diet and cognitive performance between 1998 and 2000 were included in the analysis. of twins, 34% were monozygotic (genetically identical) and 66% were dizygotic (50% identical genes).
Baseline dietary intake was assessed using a food frequency questionnaire. Dietary intake data were used to calculate diet scores for the MED and MIND dietary patterns. A higher nutritional score is indicative of higher adherence to the respective diets.
Participants’ cognitive performance was assessed at baseline and after ten years (2008 – 2010). Six types of cognitive functions were examined, including reaction speed, spatial working memory, episodic memory, visual episodic memory, decision time, and visuospatial working memory.
Fecal samples were collected from the participants at the 10-year follow-up to analyze the gut microbiota.
Change in adjusted mean (SE). Age-related cognitive ability and span length over 10 years in MZ twins discordant for MIND and MED diet score
Important observations
Assessment of the effect of dietary patterns on baseline cognitive performance revealed no significant correlation between MED diet scores and cognitive test scores. For the MIND diet, each 1-point increase in diet score was found to be associated with faster reaction time and better visual episodic memory after adjusting for demographic, health, and lifestyle confounders.
Evaluation of the effect of dietary patterns on cognitive performance over a 10-year follow-up revealed that increasing adherence to the MED or MIND diet was associated with improved episodic memory.
Assessment of the effect of dietary patterns on 10-year change in cognitive performance in discordant monozygotic twin pairs revealed that the monozygotic twin with a high diet score has less decline in global cognitive ability overall. However, this difference was not statistically significant.
Within each monozygotic pair, the twin with high MED or MIND diet scores showed greater preservation of visuospatial working memory. This observation was significant for the MED diet. No significant effect of MED or MIND diet was observed on 10-year change in other cognitive performance in discordant monozygotic twins.
Regarding the relationship between dietary patterns and gut microbiota, the findings revealed that high adherence to the MIND diet at baseline was associated with higher abundance Ruminococcaceae UCG-010 (short-chain fatty acid-producing bacteria) and lower abundance Dorea at 10-year follow-up. This association became non-significant after adjustment for dietary fiber intake.
Further analysis revealed that greater abundance Ruminococcaceae UCG-010 is associated with lower decline in global cognition and improved spatial working memory at 10-year follow-up.
Importance of study
The study finds that both the MED and MIND diets could effectively preserve episodic and visuospatial working memory in middle age. These neuroprotective effects could be attributed to the high dietary fiber content and increased abundance of short-chain fatty acid-producing bacteria in the gut.
As the scientists report, the possible influence of unidentified genetic factors on the study results in the entire study population cannot be ruled out, as the same pattern of cognitive improvement has not been found in monozygotic twins.
Future studies should include longer follow-up with repeated cognitive assessments to understand the impact of nutrition on cognitive performance in older age.
