TABLE 2.
Nut consumption and cognitive performance in middle-aged and older people (aged ≥40 y)
| Author, year, country | Study design | Study population | Nut intake (type, amount) | Comparison group | Cognitive measure | Findings |
|---|---|---|---|---|---|---|
| Barbour et al., 2017, Australia (43) | RCT, crossover | n = 61 overweight (50–75 y) | High-oleic peanuts (male: 84 g 6 times/wk, female: 56 g 6 times/wk) | Nut-free diet | Memory | No differences between groups |
| Processing speed | Mean difference: 0.2; SEM: 0.3; EF: 0.27; P = 0.047 | |||||
| Verbal fluency | Mean difference: 0.6; SEM: 0.1; EF: 0.46; P < 0.001 | |||||
| Executive function | Mean difference: 0.5; SEM: 0.2; EF: 0.35; P = 0.016 | |||||
| Dong et al., 2016, China (24) | Cross-sectional | n = 894 free-living (≥50 y) | Total nuts | MoCA (cut-off for MCI) | Cognitively healthy consumed more nuts than individuals with MCI | |
| MoCA total score | No significant association1 | |||||
| Delayed memory | F = 4.87, P < 0.0011 | |||||
| Visual-spatial ability | No significant association1 | |||||
| Name | No significant association1 | |||||
| Attention | No significant association1 | |||||
| Language | No significant association1 | |||||
| Abstraction | No significant association1 | |||||
| Orientation | No significant association1 | |||||
| Nooyens et al., 2011, the Netherlands (31) | Prospective cohort (5 y) | n = 2613, free-living (≥45 y) | Total nuts | Baseline: lowest quintile of nuts intake | Global cognitive functionCognitive flexibilityMemory | β: 0.05; P < 0.012β: 0.05; P < 0.012β: 0.05; P < 0.052 |
| Processing speed | β: 0.05; P < 0.052 | |||||
| Longitudinal: nut intake as continuous variable | Global cognitive function | No significant association2 | ||||
| Cognitive flexibility | No significant association2 | |||||
| Memory | No significant association2 | |||||
| Processing speed | No significant association2 | |||||
| Martínez-Lapiscina et al., 2013, Spain (Navarra city) (39) | RCT, parallel-arm (6.5 y) | n = 522 free-living high risk of CVD (55–80 y) | Nut mix (15 g walnuts, 7 g hazelnuts, 7 g almonds) + MedDiet (MedDiet + nuts) | Low-fat diet | MMSEClock drawing test | Mean difference: 0.57; 95% CI: 0.11, 1.03; P = 0.0153Mean difference: 0.33; 95% CI: 0.003, 0.67; P = 0.04833 |
| Martínez-Lapiscina et al., 2013, Spain (Navarra city) (40) | RCT, parallel-arm (6.5 y) | n = 268 free-living high risk of CVD (55–80 y) | Nut mix (15 g walnuts, 7 g hazelnuts, 7 g almonds) + MedDiet (MedDiet + nuts) | Low-fat diet | MMSEClock drawing testRey auditory verbal learning test – immediate | No difference between groups3No difference between groups3No difference between groups3 |
| Rey auditory verbal learning test – delay | No difference between groups3 | |||||
| Verbal paired associates | No difference between groups3 | |||||
| Rey-osterrieth complex figure – immediate | No difference between groups3 | |||||
| Rey-osterrieth complex figure – delay | No difference between groups3 | |||||
| Similarities | No difference between groups3 | |||||
| Trail making test-A | No difference between groups3 | |||||
| Trail making test-B | No difference between groups3 | |||||
| Digit (forward) | No difference between groups3 | |||||
| Digit (backward) | No difference between groups3 | |||||
| Semantic verbal fluency test – animals | No difference between groups3 | |||||
| Phonemic verbal fluency test – FAS | No difference between groups3 | |||||
| Boston Naming Test | No difference between groups3 | |||||
| Rey-osterrieth complex Figure – copy | No difference between groups3 | |||||
| Incidence of MCI | No difference between groups3 | |||||
| Salama et al., 2019, Egypt (27) | Cross-sectional | n = 186 free-living (40–65 y) | Total nuts | Nonconsumers | Risk of MCI | OR: 0.88; 95% CI: 0.80, 0.98; P = 0.02 |
| Valls-Pedret et al., 2012, Spain (Barcelona) (25) | Cross-sectional | n = 447 free-living high risk of CVD (55–80 y) | Total nuts and walnuts | Digit span test Wechsler Adult Intelligence Scale (working memory) | Walnuts: β: 1.191; 95% CI: 0.061, 2.322; P = 0.0394 | |
| MMSE | No association4 | |||||
| Rey auditory verbal learning test rate | No association4 | |||||
| Verbal paired associated test (Wechsler Memory Scale) | No association4 | |||||
| Verbal fluency test | No association4 | |||||
| Color Trail Test | No association4 | |||||
| Valls-Pedret et al., 2015, Spain (Barcelona) (38) | RCT, parallel-arm (3.6–4.2 y) | n = 334 free-living high risk of CVD (55–80 y) | Nut mix (15 g walnuts, 7 g hazelnuts, 7 g almonds) + MedDiet (MedDiet + nuts) | Low-fat diet | Memory composite | MedDiet + nuts: change: 0.1; 95% CI: –0.04, 0.24Control: change: –0.16; 95% CI: -0.32, –0.01; P-difference < 0.055 |
| Frontal cognition | No difference between groups5 | |||||
| Global cognition (average of 4 timepoints) | No difference between groups5 | |||||
| MMSE | No difference between groups5 | |||||
| Rey auditory verbal learning test rate | No difference between groups5 | |||||
| Verbal paired associated test (Wechsler Memory Scale) | No difference between groups5 | |||||
| Verbal fluency test | No difference between groups5 | |||||
| Digit span test Wechsler Adult Intelligence Scale (working memory) | No difference between groups5 | |||||
| Color Trail Test part 1 | No difference between groups5 | |||||
| Yuan et al., 2016, China (34) | Case-control | n = 276 (138 MCI, 138 age and sex-matched controls) (55–75 y) | Total nuts | Nut intake was not different between MCI and control groups (P = 0.523) |
Adjusted for age, gender, nationality, BMI, and education level.
Adjusted for age, sex, education, total energy intake (separate for energy from fat, energy from alcohol and energy from other sources), intake of other fruits, vegetables, legumes, and juices, serum
HDL cholesterol, systolic blood pressure, usage of blood pressure-lowering medication, waist circumference, coffee consumption, smoking, physical activity, vitality, mental health, and the baseline level of cognitive function (in the longitudinal data analyses).
Adjusted for sex, age, education, family history of cognitive impairment or dementia, APOE ɛ4 allele, hypertension, dyslipidemia, diabetes, smoking status, alcohol intake, BMI, physical activity, and total energy intake.
Adjusted for gender, age, education, BMI, smoking, APOE ɛ4 allele, physical activity, diabetes, hypertension, and hyperlipidemia.
Adjusted for sex, baseline age, years of education, marital status, APOE ε4 allele, ever smoking, baseline BMI, energy intake, physical activity, type 2 diabetes mellitus, hyperlipidemia, ratio of total cholesterol to HDL cholesterol, statin treatment, hypertension, use of anticholinergic drugs, time of follow-up, propensity score for group allocation. CVD, cardiovascular disease; EF, Cohen's d effect size; MCI, mild cognitive impairment; MedDiet, Mediterranean diet; MMSE, Mini-Mental State Examination; MoCA, Montreal Cognitive Assessment; RCT, randomized controlled trial.