TABLE 1.

Details of included reviews, including reference, a type of review, objective, domains considered, population, review method, and outcomes. Presented with guidance documents first, followed by systematic reviews, non-systematic reviews, and finally opinions and editorials

Reference	Type of review	Objective	Domains	Population	Methods	Outcomes
De Jager et al. (2014) [13]	Guidance document	Provide guidelines for those planning to study the effects of nutrition on cognition Identify/apply criteria for validation of tests	Memory (including verbal, visual, spatial, and verbal working memory), selective and sustained attention, executive function, information processing speed, and global cognitive function.	Adults	Expert group Review of domain/paradigm sensitivity to polyphenol, B vitamin, and n3FA intervention trials	Criteria should include: Everyday functional or behavioral relevance, Neural mechanisms, Appropriate target populations, Paradigm’s utility, validity, and reliability, Established sensitivity to nutraceuticals (Acute or Long-term effects). Domain with the most evidence for effect of nutrition is verbal memory.
Benton et al. (2005) [19]	Guidance document	To make recommendations for the assessment of memory	Memory (details the different types using the basic “textbook” model). Also reviews changes in different aspects of memory in aging and dementia.	Adults	Expert opinion	Gives examples of commonly used tests in mainstream Psychology research, for example, Wechsler, MMSE, word association/paired associates etc. Consider reliability, validity, normative data.
Kallus et al. (2005) [20]	Guidance document/review	To give an overview of changes in different facets of attention and psychomotor functions beyond 50 y, as well as assessment methods for attention and psychomotor performance.	Attention span (aka working memory), selective attention, vigilance, focused attention, shifting attention, and divided attention. Evaluates mediators/moderators of task performance that might be dependent on age, for example, high performance variance and of age-related confounding variables like health status.	Adults over 50 y	Expert opinion/review of attentional aging studies, and effects of specific nutrients	Gives examples of commonly used tests in mainstream Psychology research, for example, Stroop, Trail making, Digit Symbol Substitution Test, Vigilance Test.
Westenhoefer et al. (2004) [21]	Review and guidance document	Review existing methodologies, which may be used to substantiate and validate such claims of desirable effects of foods on mental state and performance	1) mood; 2) arousal, activation, vigilance, attention, and sleep; 3) motivation and effort; 4) perception; 5) memory; and 6) intelligence. Potential claims related to the area of mental state and performance are listed Scientific constructs and concepts related to this field are defined and methods of assessment are reviewed.	Adults	Non-systematic review and expert opinion	Validated methodologies do exist to generate scientific evidence in this area. Factors that should be considered include language and culture, size of the effect, amount of active substance, and subpopulations.
Wesnes (2010) [22]	Guidance document	Present a set of criteria that any test or test battery should fulfill before being considered “fit for the purpose”	Attention, working memory, episodic memory, motor control, and aspects of executive function.	All	Expert opinion	Utility, reliability, sensitivity, and validity are the independent minimum requirements Clinical relevance, everyday behavioral relevance, and normative databases are also highly desirable
Martini et al. 2018 [23]	Guidance document	To improve the quality of applications provided by applicants to the European Food Safety Authority, through an appropriate choice of outcome variables and methods of measurement	Global cognitive function, attention and sustained attention, alertness, memory, problem solving, abstract reasoning, intelligence, learning, language, implicit memory.	All	Expert group review	To successfully substantiate health claims through EFSA, it is necessary to select appropriate outcome variables and methods of measurement. Gives guidance on selection of appropriate measures, including a critical evaluation of individual tests based on the review.
Reference	Type of review	Objective	Domains	Population	Methods	Outcomes
Macready et al. (2010) [24]	Review	Review the cognitive methods used in existing randomized controlled studies that have explored the effects of nutrition on human cognition, with a view to identifying domains and individual tasks within those domains that have shown greatest sensitivity to chronic supplementation.	Executive function (focused attention, sustained attention, inhibition, switching/shifting, updating, decision-making, planning, visual search, and verbal fluency), Memory (working, episodic, semantic, procedural, implicit, prospective, short-term, long-term, recognition, verbal, visuospatial, and numerical), Motor (psychomotor processing speed, and motor function), perception, IQ (crystallized intelligence and fluid intelligence)	Adults	Systematic review	“Scattergun” approach to task selection limits the ability to make reliable comparisons across studies. Some important aspects of cognition are under-represented, for example, prospective memory. Executive function, and spatial working memory may be most sensitive. Task demand is important. Need to 1) pay closer attention to animal studies and to previous human work when identifying appropriate cognitive tests, 2) consider whether tasks are appropriate to the target population, 3) take greater care to avoid statistical artifacts likely to bring about null findings, such as lack of power, and type I errors, and 4) include more than a single task within a domain (for example, 2 executive function tasks) to determine whether a null effect for a particular nutrient is a real finding or reflects a lack of task sensitivity to the nutrient.
Pase and Stough (2014) [8]	Perspective	To review and describe current theories of cognitive ability and explain, with working examples, how such theories can guide the handling of cognitive outcomes in nutrition research.	Carroll’s cognitive model [29] and the Cattell–Horn model [30] are the main focus	All	Non-systematic review Application of CDC model to group cognitive tests from a collection of nutrition research clinical trials	Agreement on a taxonomy is needed Carroll’s cognitive model [29] and the Cattell–Horn model [30] can be used to guide Avoid combining cognitive test data based on arbitrary rules
Schmitt et al. (2005) [25]	Primer for non-experts	Provide those individuals who lack a background in experimental cognitive science with a basic overview of the main concepts, issues, and pitfalls of human cognitive research.	Executive functions (reasoning, planning, concept formation, evaluation, and strategic thinking), memory functions (short-term and long-term encoding, storage and retrieval functions, and working memory), attention functions (selective, divided, and sustained), perceptual functions, psychomotor functions, and language skills	All	Expert opinion	Discusses some general principles for task selection including basing decisions on prior research, measuring confounding factors such as arousal or mood, considering speed/accuracy trade-offs, length of the test battery (fatigue), test-retest variability, population appropriateness and homogeneity, ecological validity
Dangour, and Allen (2013) [26] Pase and Stough (2013) [27] Kennedy (2013) [28]	Dialog	In the original editorial, Dangour and Allen [26] aim to review the evidence for n3FA affecting brain function. This is followed by 2 replies via letters to the editor.	Pase and Stough [27] suggested taxonomy: language, reasoning, memory and learning, visual perception, auditory perception, idea production, cognitive speed, knowledge and achievement, and miscellaneous abilities	All	Expert opinion	In the original editorial Dangour, and Allen [26] suggest that a lack of preregistration of primary end points, and heterogeneity of test used in cognitive intervention trials affects reliability of outcomes. Pase and Stough [27] aimed to identify an agreeable cognitive taxonomy and suggests Carroll’s “Three Stratum Theory” [29]. Kennedy [28] disagreed on the basis that 1) it would be hard to map task outcomes onto Carroll’s factor analyzed domains, and 2) cognitive taxonomies are fluid and evolving including Carroll’s.

In the population column, the term “All” has been used to classify reviews that have a more general focus of cognition and are therefore not limited to a specific population. n3FA, ω-3 FAs; EFSA, European Food Safety Authority; IQ, Intelligence Quotient; MMSE, Mini-Mental State Examination.