TABLE 1.

Overview of the findings from nine detected studies on the impact of diet/nutrition on cognitive functions among healthy older people.

Author, type of study, country, follow-up	Study sample	Type of diet and its intervention	Main outcome measures and assessed cognitive domains	Findings
Chai et al. (2019) (RCT) United States Follow-up: None.	37 healthy seniors, age range: 65–80 years, 17 males, 20 females. 20 participants were in the intervention group and 17 in the control group.	The intervention group received two cups of Montmorency tart cherry juice per day for 12 weeks.	Montreal Cognitive Assessment Test, CANTAB assessing episodic visual memory and new learning, attention, speed of response and movement, working memory, and a subjective memory questionnaire.	The intervention group had higher contentment with memory scores (mean difference of 2.7; 95% CI: 1.2 to 4.2; p = 0.02), especially in spatial working memory, as well as in visual sustained attention.
Danthiir et al. (2018) (RCT) Australia Follow-up: None.	391 participants, age range: 65–90, 195 seniors in the intervention group, 196 seniors in the control group.	The intervention group received 1720 mg DHA and the control group 600 mg eicosapentaenoic acid or low-polyphenolic olive oil daily in the form of capsules for 18 months.	MMSE, Sternberg’s number and letter memory scanning, Simon task, Stroop test, Australian Short-Form Health Survey, the Yale Physical Activity Scale, the Dietary Questionnaire, Polyunsaturated Fatty Acid Questionnaire, Late Life function and Disability Instrument, Cognitive Failure Questionnaire, the Prospective and Retrospective Memory Questionnaire, the Satisfaction with Life Scale, the Positive and Negative Affect Scale, the Center for Epidemiological Studies Depression Scale, the Nottingham Sleep Survey.	Daily supplementation with 2.3 g DHA-rich fish oil for 18 months did not maintain or improve cognitive performance. A small negative main effect was found on psychomotor speed in men (intervention = -0.02, 95% CI: -0.04 to 0.00; d = 0.24, P = 0.03).
Karstens et al. (2019) (Cohort study – cross-sectional) United States.	82 healthy seniors at the age of 68.8 years, 50% males and 50% females; participants were divided into High and Low (median split) adherence groups.	Adherence to MedDiet.	Block Food Frequency Questionnaire 2005, standardized cognitive assessment battery of tests (i.e., the California Verbal Learning Tests, Trail Making Tests – Part A, Part B, and the Wechsler Test of Adult Reading), MRI, T1-weighted images, FreeSurfer 6.0 segmentation pipeline. Assessed cognitive domains: learning and memory, information processing and executive functioning.	The High MedDiet group was better at learning and memory performance [β = 0.52, SE = 0.21, t(74) = 2.53, P = 0.01, d = 1.23].
Kuroda et al. (2019) (RCT) Japan Follow-up: None.	52 healthy seniors, randomly assigned into a UHHPBR group (27 subjects) and polished WR group (25 subjects), mean age: 72.9 + 0.8 years, 25 males, 27 females.	100 g of UHHPBR per day for 2 years (intervention group) and 100 g of white rice (control group).	Revised Hasegawa’s Dementia Scale, Mini-Mental State Examination, FAB, Cognitive Assessment for Dementia, iPad version (CADi) assessed cognitive function.	A 2-y oral consumption of UHHPBR increases information processing speed (the total FAB score was greater in the UHHPBR group than in the WR group, p = 0.062, and improves apathy (p = 0.012) among healthy seniors.
Marseglia et al. (2018) (RCT) China, France, Italy, Netherlands, Poland, Sweden, United Kingdom Follow-up: 1 year.	1,279 healthy seniors, age range: 65–79 years, from five European centers. They were randomly assigned into a control group (638) and an intervention group (641).	Intervention group: individually tailored Mediterranean-like dietary advice (NU-AGE diet); control group – habitual diet. After the baseline assessment, both groups completed a seven-day food record for seven consecutive days over 2 weeks and had an interview with a trained dietician to review the records. The intervention group had a monthly education telephone calls and face-to-face meetings with a dietician.	CERAD – Neuropsychological Battery, MMSE, Babcock Story Recall Test, Pattern Comparisons, Digit Cancelation, Trail Making Tests, Word List Memory, 15-items Boston Naming Test, Constructional Praxis Test, Category fluency. Assessed cognitive domains: global cognition, perceptual speed, executive function, episodic memory, verbal abilities, and constructional praxis.	Subjects with higher adherence to the NU-AGE diet experienced considerable improvements in global cognition [β 0.20 (95%CI 0.004, 0.39), p-value = 0.046] and episodic memory [β 0.15 (95%CI 0.02, 0.28), p-value = 0.025] after 1 year, compared to those adults with lower adherence to NU-AGE diet. Both groups of subjects improved in global cognition and in all cognitive domains after 1 year.
Milte et al. (2019) (Cohort study – prospective) Australia.	617 participants, age range: 55–65 years.	Different food choices (diet variety). The study lasted from 2010–2014.	A postal survey including a 111-item Food Frequency Questionnaire, dietary guideline index (DGI-2013), Telephone Interview of Cognitive Status (TICS-m), which assessed cognitive function.	There were no associations between diet quality in 2010 and cognitive function in 2014. However, participants who reported higher dietary variety
				(B = 0.28, 95% CI 0.03, 0.52) and women who reported “sometimes” adding salt to food after cooking (B = 0.98, 95% CI 0.25, 1.71) in 2010 displayed better cognitive function in 2014. In 2014, usual consumption of higher fiber bread choices in the total sample (B = 1.32, 95% CI 0.42, 2.23), and higher diet quality (B = 0.03, 95% CI 0.00, 0.07) and greater fluid consumption (B = 0.14, 95% CI 0.01, 0.27) in men were all associated with better cognitive function.
Moran et al. (2018) (RCT) Ireland Follow-up: at 3, 6 months.	37 older people, age range: 68–83 years, 20 seniors in the intervention group and 17 in the control group, 18 males and 19 females.	The intervention group received (Smartfish), containing omega-3 polyunsaturated fatty acids (PUFAs), vitamin D, resveratrol, and whey protein. The control group placebo – 200 ml palatable, pomegranate and apple flavored juice formulations only. It lasted 6 months.	Time-Up and Go test, Cognitive Failures Questionnaire, Trail Making Test, Auditory Verbal Learning Test, Stroop test, Color and Color-Word tasks, Controlled Oral Word Association test, Digit Span test.	Only a limited beneficial impact was shown, especially for Stroop Color-Word Time (p < 0.05) in the intervention group. The intervention group demonstrated reduced task completion time at three- and six-month follow-ups, indicating enhanced performance.
Okubo et al. (2017) (cohort study – cross-sectional) Japan.	635 healthy elderly at the age of 69–71 years.	Different dietary patterns (the “Plant foods and fish” – high intakes of green and other vegetables, soy products, seaweeds, mushrooms, potatoes, fruit, fish, and green tea; “Rice and miso soup”; and “Animal food” – seasonings, shellfish, chicken, red meats, fish, seafood, and processed meats). The whole study lasted from 2010–2012.	A self-administered diet history questionnaire, Montreal Cognitive Assessment Test assessing nine cognitive domains: attention, concentration, executive functions, memory, language, visuoconstructional skills, conceptual thinking, calculation and attention.	The “Plant foods and fish” pattern, characterized by, was significantly associated with a higher MoCA-J score [MoCA-J score per one-quartile increase in dietary pattern: β = 0.56 (95% CI: 0.33, 0.79), P for trend <0.001]. In contrast, neither the “Rice and miso soup” nor the “Animal food” pattern was related to cognitive function.
Whyte et al. (2018) (RCT) United Kingdom Follow-up: 6 months.	122 older people, age range: 65–80 years. Participants were divided into four groups (3 intervention groups – 92 people) and one placebo control group – 30.	30 people received a whole wild blue-berry powder at 500 mg and 31 subjects 1000 mg and 31 people a purified extract at 100 mg (WBE111). The intervention lasted 6 months.	Rey’s Auditory Verbal Learning Task and Corsi Blocks Task were used for measuring verbal episodic memory and visual memory.	The findings show that a 3-month intervention with WBE111 can enhance episodic memory performance among healthy seniors (p < 0.05).

CANTAB, Cambridge Neuropsychological Test Automated Battery; CERAD, Consortium to Establish a Registry for Alzheimer’s Disease; CHAS, Canadian Healthy Aging Study; DHA, docosahexaenoic acid; FAB, Frontal Assessment Battery; MedDiet, Mediterranean Diet; MMSE, Mini-Mental State Examination; MRI, magnetic resonance imaging; NU-AGE, New dietary strategies addressing the specific needs of elderly population for an healthy aging in Europe; TICS-m, Telephone Interview of Cognitive Status; UHHPBR, ultra-high hydrostatic pressurizing brown rice; WR, white rice.