Globally, cognitive impairments including Alzheimer’s disease and dementia, have become a major concern. The total number of people with dementia has increased from 20.2 million in 1990 to 43.8 million in 2016 and dementia was the fifth leading cause of death accounting for 2.4 million deaths worldwide in 2016.
Diet can affect brain function through different mechanisms including the regulation of neurotransmitter pathways, synaptic transmission, membrane fluidity and signal transduction pathways. Many nutrients, such as omega-3 fatty acids, flavonoids, vitamin E, have been examined for their role in cognitive function.
Nuts are good sources of polyunsaturated fatty acids, phytosterols, polyphenols, and magnesium. Nut consumption has been shown to be beneficial for the prevention of many chronic diseases including diabetes and hypertension - both of which are risk factors for cognitive impairment.
Previous population observational studies suggest a beneficial effect of nuts on cognition. On the other hand, a few studies have shown no association between cognitive function and nuts intake.
The aims of the current study were to (1) to assess the association between nuts consumption and cognitive function among the Qatari population; (2) to test whether magnesium, hypertension, and diabetes mediate this association between nut consumption and cognitive function.
Qatar Biobank Study (QBB) is an ongoing cohort study started in 2012 with over 15,000 participants. In the current analysis, 1000 Qatari adults aged 20 years and above were randomly selected by the QBB management team. Using a self-administered questionnaire, socio-demographic information, lifestyle factors, and dietary habits were collected. In addition, medical and family history information were obtained by a nurse interview and a health examination was conducted.
Cognitive function was assessed by a computer-based test to measure the mean reaction time (MRT) and a 102 item food frequency questionnaire (FFQ) was used to assess dietary habits.
A total of 21.1% of the participants reported consuming nuts ≥4–6 times/week (high consumption) while 40.2% reported consuming ≤1 time/month (low consumption). Overall, an inverse association was found between nuts consumption and MRT and the association between nuts and MRT was mainly seen among those aged over 50 years.
The association between nuts consumption and MRT was not mediated by hypertension, diabetes, or serum magnesium.
The authors therefore conclude that habitual higher consumption of nuts is positively associated with cognitive function, especially among old adults.
The report concludes: "Nuts consumption is beneficial for cognitive function as measured by MRT, especially among those with old age, diabetes, and hypertension. Further prospective studies and randomized clinical trials are needed to assess the amount and type of nuts consumption on cognitive function."
The authors note the study has some limitations. First, MRT is the only indicator used for measuring cognitive function. Second, the sample is relatively small and most of the participants were young so results cannot be extrapolated over the general population. Third, the food frequency questionnaire used included only the frequency of the nuts consumption without specifying the amount or type of the consumed nuts. Thus, we could not estimate the actual amount (grams/day) of nuts intake. In addition, recall bias is considered another limitation in this study.
Nafea, H.; Abdelmegid, O.; Qaddourah, S.; Abdulwahab, Z.; Moawad, J.; Shi, Z.
"Higher Habitual Nuts Consumption Is Associated with Better Cognitive Function among Qatari Adults"