Table 4.
Characteristics of the reviewed studies on the effects of olive oil and its cognitive effects.
| Study | Type of Study | Intervention | Control Group | Health Status at Baseline | N and Duration |
Measures of Cognition | Significant Outcomes of the Interventions | Ref. |
|---|---|---|---|---|---|---|---|---|
| Valls-Pedret et al., 2012 | Cross-sectional | Not applicable | Not applicable | High cardiovascular risk | 477 NA |
Cognitive performance (MMSE, RAVLT, WMS, WAIS, and the Color Trail Test). | Total olive oil intake associated with immediate verbal memory. | [64] |
| Virgin olive oil intake associated with delayed verbal memory. | ||||||||
| Total urinary polyphenols associated with better immediate verbal memory. | ||||||||
| Martínez-Lapiscina et al., 2013 | RCT | Int G1: MedDiet + EVOO (1 L/week) | Low fat diet | High cardiovascular risk | 522 6.5 years |
Cognitive performance (MMSE and CDT) and dementia/MCI incidence. | EVOO vs. control: better MMSE and CDT. | [65] |
| Int G2: MedDiet + nuts (30 g/day) | EVOO: low odds ratio of MCI. | |||||||
| Martínez-Lapiscina et al., 2013 | RCT | Int G1: MedDiet + EVOO (1 L/week) | Low fat diet | High cardiovascular risk | 285 6.5 years |
Cognitive performance (MMSE, CDT, WMS, RAVLT, ROCF, BNT, FAS, WAIS-IIIR, and CDR). | EVOO vs. control: higher MMSE, ROCF immediate and delayed, FAS, and digital forward scores. | [66] |
| Int G2: MedDiet + nuts (30 g/day) | EVOO vs. nuts: higher ROCF immediate and delayed and verbal (VPA) memory. | |||||||
| Valls-Pedret et al., 2015 | RCT | Int G1: MedDiet + EVOO (1 L/week) | Low fat diet | High cardiovascular risk | 477 4.1 years (mean) |
Cognitive performance (MMSE, RAVLT, ASF, DST from WAIS, color trait test, and WMS) in 3 composites: memory, frontal, and global cognition. | MedDiet + EVOO improved frontal cognition and global cognition adjusted composites for changes from baseline. Changes were significant compared to control group. | [67] |
| Int G2: MedDiet + nuts (30 g/day) | ||||||||
| Mazza et al., 2018 | RCT | MedDiet + EVOO (20–30 g/day) | MedDiet | Healthy ≥ 65 | 180 1 year |
Cognitive performance (MMSE and ADAS-cog). | ADAS-Cog score showed greater improvement with MedDiet + EVOO vs. MedDiet. | [68] |
| Tsolaki M et al., 2020 | RCT | Int G1: High phenolic (HP)- EVOO (50 mL/day) | MedDiet | MCI (60–80 years) |
50 1 year |
Cognitive performance (MMSE, RBMT, ROCF, Trail Making Test parts A and B, ADAS-Cog, WMS DST, fluency, and CDT). | HP-EVOO improved ADAS-Cog and letter Fluency (follow-up vs. baseline) compared to control group. | [69] |
| Int G2: Moderate phenolic (MP)- EVOO (50 mL/day) | MP-EVOO improved MMSE and ADAS-Cog (follow-up vs. baseline) compared to control group. | |||||||
| Dimitriadis S et al., 2021 | RCT | Int G1: High phenolic (HP)- EVOO (50 mL/day) | MedDiet | MCI (60–80 years) |
43 1 year |
EEG resting-state with open eyes and close eyes conditions. | HP-EVOO decrease signal spectrum within 1–13 Hz and theta/beta. | [70] |
| HP and MP-EVOOs improved the flexibility index being more noticeable in the HP- EVOO group. | ||||||||
| Int G1: High phenolic (HP)- EVOO (50 mL/day) | HP-EVOO had a significant higher post-intervention reduction in non-linearity index. | |||||||
| Tzekaki E et al., 2021 | RCT/ observational |
EVOO | MedDiet | 3 groups: MCI, AD and healthy | 84 1 year |
Fibrinolytic system (levels of PAI-1, a2-antiplasmin, tPA). | EVOO reduced PAI-1, and tPA in MCI, restoring levels to those of healthy individuals. | [71] |
| AD hallmarks (levels of p-tau, Aβ1-42, Aβ1-40). | EVOO reduced p-tau in MCI, restoring levels to those of healthy individuals and maintained AB-40 levels, downregulated in MCI without EVOO. | |||||||
| Oxidative stress: levels of MDA. | EVOO reduced MDA in MCI and restoring levels of healthy individuals | |||||||
| Tzekaki E et al., 2021 | RCT/ observational |
EVOO | MedDiet | Three groups: MCI, AD and healthy | 80 1 year |
Levels of BMI1, p53, tau, p-tau, Aβ1–42, Aβ1–40, TNF-a, IL-6, and MDA. | EVOO increased BMI and decreases p53 and MDA in MCI patients. | [72] |
| IL6 and TNF-a were downregulated in MCI patients by EVOO intervention. | ||||||||
| 12-month EVOO restored AD-related biomarkers (p-tau, Aβ1–42 and Aβ1–42/Aβ-40 ratio) to normal levels in MCI. | ||||||||
| Nishi et al., 2021 | Observational | Not applicable | Not applicable | Overweight/obese + Metabolic syndrome | 6647 2 year |
Cognitive performance (MMSE, CDT, VFT-a and VFT-p, TMT A and B, DST-f and DST-b, and WAIS-III), and a global composite. | Baseline OO used as the primary oil was positively associated with changes in global cognitive function and in working memory (forward and backward DSTs). | [73] |
| Kaddoumi et al., 2022 | RCT | EVOO (1200 mg/kg of total polyphenols) (30 mL/day) | Refined OO (null polyphenol content) (30 mL/day) | MCI (55–75 years) |
26 6 months |
MRI: contrast-enhanced MRI and fMRI. | EVOO decrease BBB permeability and brain connectivity. | [74] |
| Cognitive performance (MMSE, CDR, WMS-IV). | EVOO and ROO decreased CDR and increased WMS-IV sub-sections. | |||||||
| AD biomarkers Aβ40, Aβ42, Tau, and p-tau181. | EVOO and ROO reduced Aβ42/Aβ40 ratio and p-tau/tau. | |||||||
| Marianetti et al. in 2022 | RCT | Nutraceutical formulation with SAG (50 mg), oleuropein (80 mg), vitamin B6 (1 mg), B12 (3 µg), vitamin E (15 IU), vitamin D3 (4 µg), piperine (3 mg), bacopa dry extract (100 mg) twice a day. | Absence of nutraceutical formulation | Mild AD | 18 6 months |
Cognitive performance (MMSE, CDT, RAVLT, RCF C, MA (attentive matrices), AAT, FAB, STEP, SVF, PVF). | Nutraceutical improved MMSE and CDT significantly vs. control group. | [75] |
| Memory: nutraceutical improved RAVLT-immediate and delayed recall, and RCF-immediate recall vs. a deterioration in control group. | ||||||||
| Attention: nutraceutical improved attentive matrices vs. a reduction was observed in control group. | ||||||||
| Language and speech: nutraceutical improved AAT vs. no change in control group. | ||||||||
| Executive functions: nutraceutical improved all measured indications vs. a decrease in control group. |
Alzheimer’s disease (AD); animals semantic fluency (ASF); attentive matrices (MA); clinical dementia rating (CDR); clock-drawing test (CDT); digit span test (DST) from Wechsler Adult Intelligence Scale (WAIS); extra virgin olive oil (EVOO); Frontal Assessment Battery (FAB); high phenolic extra virgin olive oil (HP-EVOO); mild cognitive impairment (MCI); mini-mental state examination (MMSE); moderate phenolic extra virgin olive oil (MP-EVOO); Progressive Matrices (Raven’s) (PVF); Rey Auditory Verbal Learning Test (RAVLT); Rey–Osterrieth complex figure copy (RCF C); randomized controlled trial (RCT); silhouettes subtest of the Visual Object and Space Perception battery (SVF); Stroop Test for executive processing (STEP); Wechsler Memory Scale (WMS); Wisconsin Card Sorting Test (AAT).