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. 2023 Oct 11;10:1218538. doi: 10.3389/fnut.2023.1218538

Table 2.

Findings of the included studies.

Study ID Olive oil consumption Control group diet Cognitive assessment Outcomes Main results
Anastasiou et al. 2017 (48) Mean ± SD (times/day): 1.4 ± 0.5 No control MMSE, Greek Verbal Learning Test, Verbal and Non-verbal Memory, the Boston Naming Test-short form, Medical College of Georgia (MCG) Complex Figure Test, verbal fluency, Anomalous Sentence Repetition, Benton’s Judgment of Line Orientation, Clock Drawing Test (CDT), Trail Making Test (TMT)-Part A, TMT-Part B, A gross estimate of Intellectual level and Graphical Sequence Test. Association of olive oil intake with cognitive status (dementia, no dementia), OR (95% CI): 1.692 (0.984–2.907)
Association with cognitive performance, beta±SE: −0.028 ± 0.033		 Olive oil intake had no significant relationship with cognition.
Bajerska et al. 2017 (53) Mean ± SD (serving/month)
Group 1: 15.6 ± 2.74
Group 2: 20.9 ± 2.70		 No control Stroop test part A, The Spatial Span (SSP) Association of olive oil intake with Stroop test part A score
Regression coefficient (95% CI): −0.33 (−0.70, 0.03)
beta: −0.21
Association of olive oil intake with SSP score
Regression coefficient (95% CI): 0.06 (0.01, 0.1)
beta: 0.28		 The consumption of olive may provide a cognitive health benefit.
Berr et al. 2009 (16) ‘Moderate use’ (39.90%): olive oil used for cooking or dressing only,
‘Intensive use’ (37.41): olive oil used for cooking and dressing		 No use of olive oil Benton Visual Retention Test (BVRT), MMSE, Isaacs Set Test (IST) Adjusted longitudinal relationship between cognitive decline and olive oil consumption, OR (95% CI)

  1. Global cognitive functioning

Control: 1
Moderate use: 0.94 (0.78–1.13)
Intensive use: 0.95 (0.78–1.15)

  1. Verbal fluency OR (95% CI)

Control: 1
Moderate use: 0.96 (0.80–1.16)
Intensive use: 0.85 (0.70–1.03)

  1. Visual memory OR (95% CI)

Control: 1
Moderate use: 0.91 (0.77–1.09)
Intensive use: 0.83 (0.69–0.99)		 Extensive consumption of olive oil was linked to a reduced chance of cognitive deficit in visual memory and verbal fluency and visual memory. The correlation was non-significant when the MMSE was used to measure global cognitive functioning.
Fischer et al. 2018 (23) Never: 36.3%
<1 time/week: 12.2%
1 time/week: 8.2%
Several times/week: 32.2%
Every day: 11.1%		 No control Structured interview from the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) was used to diagnose Alzheimer’s type dementia, multi-infarct dementia and dementias of other etiology (SIDAM). Relationship between AD incidence and olive oil consumption, HR (95% CI): 1.00 (0.93; 1.07)
Relationship between memory decline and olive oil consumption, unstandardized regression coefficient (95% CI): −0.03 (−0.09; 0.04)		 The investigation showed no relationship between high olive oil consumption and the risk of AD or memory decline. Unexpectedly, there was a trend for higher olive oil intake to be related to memory decline in women.
Galbete et al. 2015 (49) Mean ± SD (g/day)
Low MeDi score: 15 ± 16
Middle MeDi score: 19 ± 15
High MeDi score: 23 ± 16		 No control Telephone interview for cognitive status-modified (TICS-m) Cognitive function changes, mean (95% CI): −0.37 (−0.68—0.06) A higher adherence to olive oil consumption might be correlated with superior cognitive functioning.
Martínez-Lapiscina et al. 2013 (22) The “MeDi + EVOO” group received EVOO 11/week. Low fat diet Rey Auditory Verbal Learning Test (RAVLT), MMSE, Clock Drawing Test (CDT), Rey-Osterrieth Complex Figure, Verbal paired associates, Trail Making Test A and B, Digit (forward and backward), Boston Naming Test, Semantic Verbal Fluency Test; Phonemic Verbal Fluency Test. Mean cognitive assessment scores after follow-up, by group (95% CI)

  1. MMSE

MedDiet+EVOO: 28.14 (27.72–28.56)/MedDiet+Nuts: 28.83 (27.36–28.30)/Control: 27.48 (27.07.27.90)

  1. CDT

MedDiet+EVOO: 5.53 (5.19–5.86)/MedDiet+Nuts: 5.20 (4.85–5.56)/Control: 5.07 (4.72–5.42)

  1. RAVLT (immediate)

MedDiet+EVOO: 32.90 (31.06–34.74)/MedDiet+Nuts: 31.28 (29.04–33.53)/Control: 30.62 (28.61–32.63)

  1. RAVLT (delay)

MedDiet+EVOO: 5.81 (5.25–6.37)/MedDiet+Nuts: 5.17 (4.53–5.81)/Control: 5.21 (4.59–5.84)

  1. VPA

MedDiet+EVOO: 13.43 (12.66–14.20)/MedDiet+Nuts: 12.05 (11.25–12.84)/Control: 12.81 (12.01–13.61)

  1. ROCF (immediate)

MedDiet+EVOO: 13.88 (12.49–15.27)/MedDiet+Nuts: 10.94 (9.54–12.34)/Control: 11.95 (11.47–13.03)
 The long-term EVOO-rich MeDi intervention led to improved cognitive functioning, compared with the control group. However, most cognitive domains were not significantly different. Those in the EVOO-rich MeDi had less MCI than those on the control group.

  1. ROCF (delay)

MedDiet+EVOO: 13.27 (11.70–14.84)/MedDiet+Nuts: 10.83 (9.44–12.22)/Control: 11.13 (9.84–12.43)

  1. Similarities

MedDiet+EVOO: 10.90 (9.78–12.03)/MedDiet+Nuts: 10.64 (9.44–11.83)/Control: 10.11 (9.19–11.03)

  1. TMT-A

MedDiet+EVOO: 65.50 (58.84–72.16)/MedDiet+Nuts: 71.57 (64.59–78.55)/Control: 70.79 (63.60–77.98)

  1. TMT-B

MedDiet+EVOO: 199.58 (171.48–227.69)/MedDiet+Nuts: 232.41 (206.91–257.91)/Control: 220.19 (195.51–244.88)

  1. Digit (forward)

MedDiet+EVOO: 7.80 (7.38–8.22)/MedDiet+Nuts: 7.40 (7.01–7.79)/Control: 6.90 (6.55–7.24)

  1. Digit (backward)

MedDiet+EVOO: 4.44 (4.03–4.86)/MedDiet+Nuts: 4.51 (4.09–4.94)/Control: 4.20 (3.91–4.49)

  1. SVFT-Animals

MedDiet+EVOO: 13.05 (12.20–13.91)/MedDiet+Nuts: 12.17 (11.27–13.07)/Control: 12.16 (11.32–12.99)

  1. FVFT-FAS

MedDiet+EVOO: 25.66 (23.58–27.74)/MedDiet+Nuts: 23.34 (21.14–25.54)/Control: 21.29 (19.44–23.14)

  1. BNT

MedDiet+EVOO: 47.27 (45.66–48.88)/MedDiet+Nuts: 45.43 (43.69–47.17)/Control: 47.19 (45.91–48.48)

  1. ROCF (copy)

MedDiet+EVOO: 29.87 (28.62–31.11)/MedDiet+Nuts: 28.13 (26.63–29.62)/Control (low-fat diet): 28.13 (26.85–29.41)
Mazza et al. 2018 (50) The intervention group “MeDi + EVOO” received EVOO 20–30 g/day. MeDi alone MMSE, ADAS-cog, Verbal Fluency (VF), Beck Depression Inventory-II (BDI-II), Instrumental Activities of Daily Living (IADL) scales and Activities of Daily Living (ADL) Mean change within groups (before vs. after), mean ± SD

  1. MMSE

Intervention: 24.5 (1.5) vs. 25.9 (1.3)/Control: 24.6 (1.3) vs. 25.6 (1.8)

  1. ADAS-Cog

Intervention: 15.3 (5.2) vs. 12.4 (4.6)/Control: 14.0 (4.5) vs. 12.5 (3.6)

  1. ADL

Intervention: 6.0 (0.1) vs. 6.0 (0.1)/Control: 6.0 (0.1) vs. 6.0 (0.1)

  1. IADL

Intervention: 8.0 (0.2) vs. 8.0 (0.1)/Control: 8.0 (0.1) vs. 8.0 (0.1)

  1. VF

Intervention: 23 (7) vs. 25 (6)/Control: 25 (6) vs. 25 (7)

  1. BDI-III

Intervention: 13 (8) vs. 12 (6)/Control: 11 (7) vs. 11 (6)		 Individuals who followed the Mediterranean Diet (MeDi) along with a small dose of extra virgin olive oil (EVOO) experienced a greater short-term improvement in cognitive function scores compared to those following the MeDi alone. EVOO, being the finest quality olive oil, is believed to potentially offer a neuroprotective benefit.
Psaltopoulou et al. 2008 (4) Mean ± SD (g/day)
Men: 52.4 ± 22.5
Women: 46.3 ± 20.3		 No control MMSE Association between one SD more of olive oil consumption and MMSE score, regression coefficient (95% CI): 0.20 (−0.11, 0.51) Olive oil had a positive non-significant correlation with the MMSE score.
Tsolaki et al. 2020 (51) Group 1 received 50 mL/day Greek early harvest EVOO
Group 2 received 50 mL/day Greek EVOO		 MeDi Alzheimer Disease Assessment Scale-Cognitive (ADAS-Cog), Rivermead Behavioral Memory Test-Story Immediate and Delayed recall, Trail Making Test parts A & B, MMSE, Rey Osterrieth Complex Figure Test copy and delayed recall, Wechsler Memory Scales, Digit Span Forward and Backward, Letter and Category Fluency Test, Clock-drawing Test Mean change within groups (before vs. after), mean ± SD

  1. MMSE

Group 1: 27.9 ± 1.8 vs. 28.8 ± 1.7/Group 2: 26.6 ± 1.3 vs. 28.0 ± 1.4/Control: 28.0 ± 1.8 vs. 28.1 ± 1.8

  1. ADAS-Cog

Group 1: 12.6 ± 4.8 vs. 9.5 ± 4.4/Group 2: 15.2 ± 3.2 vs. 10.1 ± 4.2/Control: 15.3 ± 11.6 vs. 15.3 ± 11.6

  1. Clock Drawing

Group 1: 4.1 ± 0.9 vs. 4.3 ± 0.9/Group 2: 4.5 ± 0.8 vs. 4.19 ± 1.0/Control: 4.6 ± 0.6 vs. 4.5 ± 0.9

  1. Clock Copy

Group 1: 4.6 ± 0.5 vs. 4.6 ± 0.6/Group 2: 4.6 ± 0.6 vs. 4.75 ± 0.4/Control: 4.9 ± 0.3 vs. 4.9 ± 0.3

  1. Trail Making A

Group 1: 56.9 ± 18.6 vs. 65.6 ± 36.5/Group 2: 63.9 ± 30.9 vs. 64.5 ± 32.0/Control: 58.9 ± 22.1 vs. 55.4 ± 19.6

  1. Trail Making B

Group 1: 224.7 ± 112.2 vs. 234.1 ± 127.0/Group 2: 270.7 ± 146.3 vs. 238.8 ± 118.4/Control: 215.5 ± 116.4 vs. 198.9 ± 157.3
 Extended treatment with high phenolic early harvest extra virgin olive oil (HP-EH-EVOO) or moderate phenolic extra virgin olive oil (MP-EVOO) resulted in significant improvements in cognitive functioning, when compared to the MeDi alone. These improvements were observed irrespective of whether the APOE 4 gene was present.

  1. Digit Span Forward

Group 1: 6.1 ± 1.2 vs. 5.2 ± 0.7/ Group 2: 5.4 ± 1.1 vs. 5.1 ± 0.7/Control: 5.4 ± 0.8 vs. 5.6 ± 0.9

  1. Digit Span Backward

Group 1: 4.1 ± 1.3 vs. 3.9 ± 0.8/Group 2: 3.5 ± 1.0 vs. 3.5 ± 0.8/Control: 4.1 ± 1.3 vs. 4.3 ± 1.1

  1. Logical Memory I

Group 1: 12.9 ± 3.0 vs. 12.4 ± 2.2/Group 2: 11.8 ± 3.5 vs. 11.5 ± 3.6/Control: 10.2 ± 4.2 vs. 10.7 ± 4.5

  1. Logical Memory II

Group 1: 12.6 ± 2.5 vs. 12.1 ± 2.2/ Group 2: 10.9 ± 4.3 vs. 11.3 ± 4.3/Control: 9.5 ± 4.2 vs. 10.2 ± 4.8

  1. Letter Fluency

Group 1: 10.9 ± 3.8 vs. 13.3 ± 4.2/ Group 2: 10.0 ± 3.3 vs. 10.3 ± 2.5/Control: 18.6 ± 10.8 vs. 21.7 ± 13.9

  1. Category Fluency

Group 1: 17.7 ± 2.9 vs. 17.9 ± 3.3/ Group 2: 15.7 ± 2.6 vs. 15.4 ± 3.7/Control: 26.9 ± 14.5 vs. 27.5 ± 17.2
Valls-Pedret et al. 2012 (52) Mean (range) (mL/day)
Total olive oil: 38 (0–75)
Virgin olive oil: 4 (0–70)		 No control RAVLT (immediate and delayed recall) Association between total olive oil per 10 g/d and RAVLT (immediate recall)

  • Regression coefficient (95% CI): 0.755 (0.151 to 1.358)

  • Standardized regression coefficient: 0.109

Association between overall olive oil per 10 g/d and RAVLT (delayed recall)

  • Regression coefficient (95% CI): 0.163 (0.010 to 0.316)

  • Standardized regression coefficient: 0.094

 Increased consumption of both overall olive oil and virgin olive oil were correlated with enhanced memory function and global cognition.
Talhaoui et al. 2023 (54) Number of servings per week, mean (SD):
Total: 4.3 (4.9)
Cognitively normal: 6.1 (4.7)
Cognitively impaired: 3.4 (4.9)		 No control MMSE Association between olive oil consumption and cognitive impairment, ORa (95% CI): 0.906 (0.823–0.997) The consumption of olive oil served as a protective factor against cognitive deterioration.

EVOO, extra virgin olive oil; MMSE, Mini–mental state examination; MeDi, Mediterranean diet; MCI, mild cognitive impairment; AD, Alzheimer’s disease; SD, standard deviation; HR, hazard ratio; OR, odds ratio; SE, standard error; CI, confidence interval.