Dietary defense against cognitive decline

In a recent study published in the journal Nutrients, Researchers investigated the association between dietary mineral consumption and the risk of cognitive impairment (CI) in elderly Spanish individuals. CI classification was performed using the Montreal Test of Cognitive Assessment (MoCA), a highly sensitive and specific but rarely used methodology. The study findings revealed that 54.2% of the 201 participants had CI (MoCA < 26). Increased intake of iron and manganese in women reduced the risk of CI in women. However, no association could be established between mineral intake and CI in men.

Study: Association between mineral intake and cognition assessed by the Montreal Cognitive Assessment (MoCA): A cross-sectional study. Image credit: Created with the help of DALL·E 3

Can we prevent neurodegeneration with diet?

Modern medicine has increased human life expectancy, increasing the incidence of chronic conditions associated with aging, including cancer, cardiovascular disorders, and neurodegenerative diseases. Dementia, a group of neurological conditions characterized by memory loss and other severe thinking disorders, is one of the most common conditions in older adults. It is estimated to affect 50 million individuals worldwide, with an additional 10 million patients annually.

The role of MCI in dementia

Dementia pathology often begins as mild cognitive impairment (MCI), identified by subjective expert observation and objective comparisons with the patient’s previous level of functioning. While MCI can be delayed by behavioral and lifestyle changes (diet, hypertension therapy, cognitive stimulation), there are no pharmacologically approved ‘cures’ for the condition. MCI patients over the age of 65 have a 5-fold increased risk of developing dementia (especially Alzheimer’s disease (AD)) compared to adults without MCI.

Lifestyle interventions: A glimmer of hope

Studies report that more than 50% of MCI patients progress to dementia within five years of developing MCI, leading experts to consider MCI a critical stage for lifestyle modification interventions, which can delay or even reverse MCI before the onset of AD. Physical activity, smoking/alcohol cessation, and dietary interventions remain the best studied of these interventions.

Neurological benefits of nutrition

Dietary patterns with beneficial neurological associations have been identified, including the Mediterranean diet, the Dietary Approaches to Stop Hypertension (DASH), and the Mediterranean Diet to Delay Neurodegenerative (MIND) intervention. Research on the link between neurology and nutrition has focused on clinical outcomes, with limited evidence on the mechanistic influences of biomolecules and individual dietary components such as vitamins, minerals, and fatty acids.

Minerals including iron, copper, zinc, magnesium, manganese and selenium are thought to be linked to cognitive functioning, given their role in DNA repair and their antioxidant properties. However, this hypothesis has not been formally tested within a structured scientific framework.

Study design and methods

In this study, researchers tested the association between dietary mineral intake and cognitive impairment. Participants for the study were selected from the cohort “Cognitive and neurophysiological characteristics of people at high risk for developing dementia: a multidimensional approach” (COGDEM). The cross-sectional study initially included 262 Spanish individuals, of whom 201 met the inclusion criteria. Inclusion criteria included baseline Mini-Mental State Examination (MMSE) scores ≥ 24 and a Geriatric Depression Scale (GDS) short-form score ≤ 5.

Data collection and evaluation

Data collected from the study cohort included health and socio-demographic data, three-day food consumption (diet) records, anthropometric data, physical activity measurements, genotyping, and neuropsychological assessments.

Health and sociodemographic data were collected through a questionnaire that recorded work status, level of education, and chronic medical conditions (especially depression, hypertension, and diabetes). Food data were collected using DIAL diet analysis software. Nutrients of interest included energy (kcal/day), magnesium (mg/day), iron (mg/day), copper (µg/day), selenium (µg/day), manganese (mg/day), and zinc ( mg/day). Minerals were standardized to caloric intake using the Willett residual model. The Dietary Reference Intake (DRI) was used to calculate the relative contribution of minerals.

Anthropometric data included weight, height and body mass index (BMI) collected according to the guidelines of the International Society for the Advancement of Kinanthropometry (ISAK). Physical activity data were collected using an accelerometer attached to the right hip for seven days.

Genotyping was performed to identify and investigate the apolipoprotein E (APOE) allele in participants (ie, rs7412 and rs429358 polymorphisms). Based on genotyping results, individuals are categorized as carriers (APOE ε4+) or noncarriers (APOE ε4−) of the ε4 allele. This allele is strongly associated with AD.

Neuropsychological tests included the GDS depression test, the MMSE to assess immediate memory, attention, numeracy and language abilities, and the Montreal Cognitive Assessment (MoCA).

“The MoCA is a cognitive screening tool that helps detect mild cognitive impairment (MCI) (37). This test has been validated for the Spanish population. This test studies various abilities such as attention, concentration, memory, language and executive functioning.”

The MoCA is a 30-point test with scores < 26 suggesting MCI. Since the clinical assessment of MCI was not included in this study, MoCA < 26 was taken as the MCI classification criterion.

Key findings of the study

Of the 201 participants included in the study, 63.2% were women, with an average age of 59.8 years. MoCA assessments identified 54.3% of participants with MCI (34.3% women and 19.9% ​​men). Educational status was the only non-dietary variable observed to play a role in CI – the higher the educational status, the lower the likelihood of MCI. Other results of anthropometry, exercise and genotyping did not show a statistically significant association with the risk of CI.

The most significant dietary associations were the daily recommended intake (DRI) of iron and manganese in women – a higher intake of these minerals was associated with a lower prevalence of CI. Copper DRI contributions in women were also positively correlated with beneficial CI outcomes, although this interaction was not as significant as that for iron and manganese.

Gender-specific results

Surprisingly, no association could be made between any dietary minerals and positive CI results in male participants.

Concluding remarks and future directions

This study investigates the association between common dietary minerals and cognitive impairment as measured by the MoCA test. The results emphasize the importance of high consumption of iron and manganese, especially in women. These minerals, and to a lesser extent, copper, provide a protective effect against the progression of MCI and the onset of AD. No correlation was found between mineral intake and cognitive abilities in men.

“Interventions and follow-up studies monitoring dietary intake and nutritional status (including biochemical parameters) are needed to confirm the possible protective effect of iron and manganese intake on cognitive impairment and to further explore the differences found in these associations between mineral intake and cognitive function according to gender.”