Frequent nut consumption may help delay cognitive decline in older adults, even over a relatively short 2-year period, according to new research (1).

The prospective cohort study, just published in the American Journal of Clinical Nutrition, involved 6,630 older Spanish adults, aged 55-75 years, at risk of cognitive decline, and with overweight/obesity and metabolic syndrome.

Dementia is the second leading cause of death in Australia, and by 2058, the number of Australians with dementia is expected to double (2). Currently, there are no effective curative treatments, so reducing the risk of cognitive decline, including through a balanced diet, is crucial (3,4).

About the study:

At the start of the study, participants completed a food frequency questionnaire that assessed their usual intake of different foods. Nut consumption (based on a serve size of 30g) was categorised as:

• <1 serving/week
• 1-2 servings/week
• 3-6 servings/week, and
• 7 or more servings/week.

Average (mean) daily nut consumption was 1.7g and 43.7g in the lowest and highest consumption categories, respectively, at baseline.

Cognitive performance (using eight neuropsychological tests) was assessed at baseline and after two years. From this, composite measures (scores) for three cognitive domains (attention, executive function, and general cognition) and one ‘global assessment of cognitive function’ were calculated for each participant.

The 2-year change in these four measures was used to track changes in cognitive performance.

The key findings:

Higher frequency of nut consumption was linked with favourable changes in cognitive performance.

According to the study authors, this suggests a potential relationship between nut consumption and a delay in cognitive decline over a 2-year period.

And specifically, study participants consuming 3-6 servings of nuts per week had a better change in cognitive performance at 2 years than those consuming <1 serving per week.

Did you know? Two PREDIMED sub-studies reported improvements in cognitive function in participants randomised to a Mediterranean diet intervention, supplemented with 30g/day mixed nuts, after a mean of 6.5 years or 4.1 years, compared with those in the low-fat diet control group (5,6).

How do nuts contribute to cognitive health?

Oxidative stress, neuroinflammation, and reduced blood flow are considered crucial mechanisms that trigger formation of arterial plaques, and induce cell death and dysfunction, leading to cognitive decline and neurodegenerative diseases (1).

Nuts are nutrient-dense foods, rich in bioactive compounds.

They offer a unique combination of healthy fats, plant protein, dietary fibre, vitamins and minerals, phenolic compounds and phytosterols, which have anti-inflammatory, antioxidant, and other neuroprotective effects.

In a newly-published randomised trial 28 healthy participants (all in their sixties) were given 60g mixed nuts/day for 16 weeks (7). After nut consumption, cerebral blood flow, a marker of brain vascular function, was higher in certain regions of the brain, compared with control. And some aspects of cognitive performance (visuospatial memory, and verbal memory) also improved.

The bottom line:

This new study concluded that frequent nut consumption may help delay cognitive decline in older adults with overweight/obesity, metabolic syndrome, and at risk of cognitive decline, even over a relatively short 2-year period. While more research is needed in this area, this exciting finding adds to the body of scientific research – providing another reason why we should all aim to eat a daily handful of nuts! 

Did you know? Only 2% of Australians eat the target 30g of nuts a day. The average intake is just 4.6g a day (8).