It has been presumed that the global prevalence of dementia will increase substantially due to the progressive aging of the global population. To gain further insights into this problem, the Mediterranean-Dietary Approaches to Stop Hypertension Diet Intervention for Neurodegenerative Delay (MIND) study tries to study the impact of diet on cognitive health.
MIND recommends the intake of nuts, green leafy vegetables, whole grains, berries, beans, seafood, and virgin olive oil. It also emphasizes reducing the consumption of red meat, processed food, high-saturated-fat foods, sugary products, and fried foods.
Around seventeen population-based studies conducted in Sweden, Australia, France, the US, Spain, Israel, Brazil, and the Netherlands, have analyzed the association between MIND and cognitive health. These studies aimed to understand the effect of MIND adherence on cognitive abilities and performance. Interestingly, among the aforementioned seventeen studies, two demonstrated cognitive decline, and seven revealed a gradual decline in one or more cognitive abilities in individuals with greater MIND adherence.
One study reported cognitive decline among a subset of older participants. On the contrary, some studies indicated a significantly lower risk of dementia with greater MIND adherence. In most of the studies, MIND was not fully characterized, or a specific food component that influenced MIND was excluded.
About the study
A recent Nutrients study evaluated adherence to the MIND dietary pattern in the UK Biobank (UKB). UKB is a rich source of phenotypic, genetic, and follow-up data. This data was used to test the hypothesis that high adherence to MIND leads to superior cognitive ability and a reduction in the risk of incident dementia. The findings of the MIND study were compared with the Alternative Healthy Eating Index (AHEI)-2010, which is commonly used for healthy dietary pattern scores.
UKB is a population cohort with more than 502,633 participants aged between 37 and 73 years. All the participants underwent a comprehensive clinical assessment at healthcare centers in England, Wales, and Scotland from 2006 to 2010. Notably, the health status of these candidates was tracked through death and health records.
Participants who completed at least two out of four Oxford WebQ at home were included in the study. The Oxford WebQ assessed the impact of a total of 206 foods and 32 beverages.
Not much evidence was found that could validate that adherence to the MIND dietary pattern was beneficial for cognitive health in the UKB. Importantly, individuals with greater adherence to MIND were among those who did not perform cognitive function tests well.
A previous study also revealed that higher adherence to MIND and AHEI-2010 was associated with poor performance in cognitive function tests, irrespective of whether the test was conducted at an assessment center or at home.
Interestingly, it was observed that the relationship between MIND adherence and cognitive function was stronger among the highly educated participants compared to the less educated group.
Adherence to MIND was not linked to the incidence of dementia in the overall study population. Interestingly, an inverse association was observed between women who strictly adhered to MIND and the prevalence of dementia. This finding was found to be consistent with the reports of AHEI-2010.
Previously, other UKB studies have also revealed unexpected observations, including higher intake of red meat/processed food/ refined grains and lower consumption of vegetables/fruits to be associated with higher cognition ability. Similar observations were also found in at least two other studies, such as the Brazilian Longitudinal Study of Adult Health, which analyzed the effect of dietary patterns on cognitive ability.
In contrast, the Quebec Longitudinal Study on Nutrition and Successful Aging revealed that higher adherence to a healthy dietary pattern, i.e., rich in vegetables, fruits, fish, poultry, and lower-fat dairy products, resulted in higher cognitive ability.
Two components, i.e., higher poultry and moderate wine consumption, were linked with better cognitive functions. Consumption of trans fat components was not associated with incident dementia. However, when the “lower butter/margarine” component was replaced with the “low butter” component, a significant increase in the risk of dementia was observed.
Although several confounders were considered in this study, there remains a possibility that the studied diet pattern was associated with other medical, lifestyle, or SES factors that caused a reducted or impaired cognitive ability. Notably, cross-sectional analyses revealed that the worst cognitive performance due to higher adherence to MIND was not linked to an increased risk of dementia.
The key strengths of the study revolve around the large sample size, rich phenotype and genetic data, and extensive diet. Scarce evidence validated the benefits of MIND adherence for cognitive health. Nevertheless, it was observed that MIND adherence could be associated with a reduced risk of dementia in females. To date, the underlying mechanism driving the association between impaired cognitive function and greater MIND adherence is unclear, and the question should be explored in the future.