Review Reports

Round 1

Reviewer 1 Report

The authors systematically reviewed the literature of beneficial effects of consumption of fruits and vegetables on cognitive functions. The paper has focuses on young people, a population that has received less research attention. Moreover, the studies included in the present review is comprehensive, and a relationship between polyphenols and improvements in cognition emerges. Therefore, the review paper adds to the literature and may contribute to a better understanding of food nutrition and human cognition. Several points in the paper should be improved.

1. The title uses "young subjects". "Subjects" refers to individuals in a sample of a specific study. "young people" or "young population" would be the correct expression. Given that the authors focuses on young people, the literature of polyphenol consumption and aging should not be discussed too much.

2. Consider to shorten the Introduction section, and to move the second paragraph on p.8 to the beginning of the paper. This paragraph talks about the importance of this topic, and should be used to justify the rationale of the paper.

3. Try not to use adjectives as titles of subsections: e.g., on pp.2-3, "Anti-inflammatory", "Neuroprotective" ...

4. Section 3.3 Cognition and age is not very relevant to the topic.

5. There are several incorrect expressions and typos: e.g., in the second paragraph on p.4, "The global cost in 2010 in United States ...", is this sentence stating information about the worldwide cost, or US? The author used "declive" through the paper, which is not an English word. In the first paragraph of section 2.1, line 71, "Consistant with ...", it should be "Consistent".  

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Comments:

The article is on polyphenols, yet the meta-analysis providing analytic summary on their health effects are not mentioned (PMID: 29742713, PMID: 27943649, PMID: 28472215) Line 61 should be “Polyphenols are widely present in fruits and vegetables, but also in other dietary sources such as nuts, whole-grains, olive oil and infused beverages (coffee, tea). Line 62 should be “presence or absence” Line 66 even though wine is one of the major sources of polyphenols its concentration is too low to reach any significant health effects thus please rephrase “highly present” Line 186 authors should notice the following: In fact, a recent umbrella review summarising the evidence from all the meta-analysis conducted on cohort studies evaluating the association between fruit and vegetable intake confirmed that exist “strongest (probable) evidence for cardiovascular disease protection; possible evidence for decreased risk of colon cancer, depression and pancreatic diseases was found for fruit intake; and colon and rectal cancer, hip fracture, stroke, depression and pancreatic diseases was found for vegetable intake. Suggestive and rather limited associations with other outcomes have been found (PMID: 30764679)”. Line 193 however umbrella review demonstrates that for now we have good evidence for stroke and depression (PMID: 30764679). line 211 Authors omitted to cohort studies demonstrating the positive association between dietary flavonoid intake and depressive symptoms (PMID: 27413131, PMID: 29695122). Authors should comment on the results of the studies, also on classes of polyphenols that exerted significant effects toward depression. I would like authors to improve the discussion of their review. It is well know that socio-economic factors may influence adherence to Mediterranean diet, intake of fruits and vegetables and thus dietary intake of polyphenols, please include a brief comment on that in the conclusion section (PMID: 31433671); please add additionally a brief comment on westernisation of the diet and problem of childhood obesity and unhealthy dietary habits (PMID: 30969153) and what are future directions of research and policies in order to prevent epidemic of obesity among young population Authors should briefly discuss recent review summarising the literature on how polyphenols regulate brain-gut axis (PMID: 29671359). I suggest general revision of the manuscript (there are some minor spelling mistakes).

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The revision has been improved in certain aspects. However, some sections were not well organized. Moreover, as the focus of the paper, cognitive function is not clearly defined. Therefore, while I recommend rejection the current revision, resubmission is encouraged.

The structure of the paper were poorly organized. Instead of systematically introducing key terms, sections jumped back and forth to cover various topics. For example, the paper started with healthy diet and talked about bioactive compounds in fruits and vegetables, and then covered physiological processes in young and older population. Readers would expect to see how these bioactive compounds influence the physiological processes in next sections. However, the paper turned back to discuss polyphenols in foods. In fact, as mentioned before, the Introduction sections is unnecessary, because this is a review paper. It would be good to focus on the main topic from the beginning. There is no need to cover literature of older population. Cognition was not defined properly. Cognitive function is different from neural processes. Likewise, cognitive impairment could be symptoms of neurological disorders, but is not neurological pathologies. Also, the use of the term "cognitive pathologies" is incorrect. Please check typos and incorrect expressions: e.g., p.1, line 29, "... is related with ..." should be "... is related to ...", and "minor occurrence" should be "low risk"; p.1, line 2, "Recent publication have ..." should be "Recent publications have ..." These types of errors occur many times throughout the paper and sometimes impede understanding of sentences.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Thank you for providing the revised version of the manuscript.

Author Response

Thank you for your comment