Frequent nut intake delays cognitive decline in older adults

Eating nuts on a regular basis provides neuroprotective benefits to older adults who are overweight or obese, have metabolic syndrome, and are predisposed to memory loss or confusion, results of a cohort study have shown.

“[F]requent 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,” the researchers said.

Nut consumption showed a positive association with 2-year changes in general cognitive function (p<0.001 for trend). In particular, participants consuming ≥3 to <7 (β z-score, 0.06, 95 percent confidence interval [CI], 0.00‒0.12) and ≥7 servings/week (β z-score, 0.13, 95 percent CI, 0.06‒0.20) had more favourable changes in general cognitive performance. [Am J Clin Nutr 2023;118:360-368]

In multivariable-adjusted models, no significant changes were observed for other cognitive domains.

“Several potential mechanisms underlying the associations between nut intake and cognitive function have been proposed,” the researchers said.

“Oxidative stress, neuroinflammation, and reduced blood flow are considered crucial mechanisms that trigger the formation of arterial plaques, induce cell death and organic dysfunction, leading to cognitive decline and neurodegenerative diseases,” they added. [Adv Nutr 2021;12:777-792]

Several studies have demonstrated the benefits of nuts in improving antioxidant status, endothelial function, and peripheral inflammation, as well as of nut constituents in reducing amyloid-beta production, aggregation, and toxicity. [Nutrients 2021;13:3269; Pharmacol Res 2018;129:115-127; Nutrients 2023;15:1000; J Am Coll Cardiol 2020;76:2282-2284]

Nut consumption also reduces the incidence of death from cardiovascular diseases, as well as helps trim down body weight and adiposity gain. [Nutr Rev 2019;77:691-709; Obes Rev 2021;2213330]

“The neurological and cardiometabolic benefits of nuts may be explained by their nutrient-dense profile and high content of bioactive compounds,” the researchers said. “Nuts are rich in nutrients like vitamin E, folate, carotenoids, and selenium, as well as different phenolic compounds, which are potent antioxidant and anti-inflammatory agents. [Nutrients 2021;13:3269; Pharmacol Res 2018;129:115-127]

Nutrients in nuts

In addition, nuts contain a high amount of unsaturated fatty acids (ie, linoleic and α-linolenic acids) that hold vasculo-protective and anti-inflammatory effects, in addition to their roles in maintaining neuronal structure and function, modulating neuronal plasticity and other metabolic processes. [Lancet Neurol 2018;17:1006-1015; Adv Nutr 2022;13:1584-1602]

“The optimal mineral composition of nuts, being high in calcium, magnesium, and potassium but devoid of sodium, has demonstrated beneficial effects on blood pressure and insulin sensitivity,” the researchers said. [Pharmacol Res 2016;111:272-282; Am J Clin Nutr 2015;101:966-982]

“Furthermore, the high content of dietary fibre, along with unsaturated fat and polyphenols, may potentially modulate gut microbiota and, subsequently, cognitive function through the gut-brain axis,” they added. [Nutrients 2020;12:3471]

The current study included a total of 6,630 adults aged 55‒75 years with overweight/obesity and metabolic syndrome. Participants completed a validated semi-quantitative food frequency questionnaire and a comprehensive battery of neuropsychological tests at baseline and at 2-year follow-up. Nut consumption was categorized as <1, ≥1 to <3, ≥3 to <7, and ≥7 servings/week (1 serving=30 g).

The researchers used composite cognitive scores to evaluate global, general, attention, and executive function domains. They also examined associations between baseline nut consumption and 2-year cognitive changes using multivariable-adjusted linear regression models.