Exercise-Induced Gastrointestinal Symptoms in Endurance Sports: A Review of Pathophysiology, Symptoms, and Nutritional Management

Round 1

Reviewer 1 Report (New Reviewer)

This is the review article on exercise-induced gastrointestinal symptoms (Ex-GIS). The point of view is very interesting. There are a few issues that should be addressed prior to the publication in dietetics.

  

1. I think it is better to make one or two figures of two primary pathways 1) the neuroendocrine-gastrointestinal pathway and 2) the circulatory-gastrointestinal pathways in the pathophysiology of Ex-GIS for the understanding of readers.

 

2. The detailed explanation on a diagnostic-therapeutic algorithm should be described in figure legend of Figure 1.

 

 

Author Response

Dear reviewer,

thank you for your suggestions that allow us to improve our work.

Please, find attached point by point responce.

sincerely,

The authors.

Author Response File: Author Response.docx

Reviewer 2 Report (New Reviewer)

The substantive value of the presented work is satisfactory, but the knowledge of the individualization of diets and the role of the gut microbiota are still little understood. The manuscript could be accepted for publication after minor revision.

I propose:  - line 4 - to add a term ,, a review" to the title,  because the authors' experiences are limited.

                   - lines 19-20 - to change the sentence -  ,, GI symptomatology which derives from strenuous exercise can be analogue to IBS and in some conditions the symptomatology meets the Rome IV Criteria for IBS" -  to ,, GI symptomatology which derives from strenuous exercise  are similar to IBS and other functional disorders of GIT defined in the Rome IV Criteria", because  these disorders have precise timelines and severity, which is difficult to assess for Ex-GIS. 

 

 

 

Author Response

Dear reviewer,
Thank you for your kind suggestion.
Please find attached the responce point by point.
Kind regard.
The authors.
Emanuela Ribichini
Giulia Scalese

Author Response File: Author Response.docx

Reviewer 3 Report (New Reviewer)

Dear Authors,

This is an interesting review topic and good writing/adequate references.

These are good findings and conclusions though not very novel.

Thank you.

Author Response

Dear reviewer,
Thank you for your opinion and your positive comment.
Kind regard.
The authors.
Emanuela Ribichini
Giulia Scalese

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The authors aim to provide a review of exercise induced gastrointestinal symptoms in endurance exercise including information on the pathophysiology and potential dietary strategies to minimize the effects. While the article is of interest, it reads like a collection of thoughts on the topic in bullet points. Often information is listed, however, there is a lack of explanation and connection between ideas. The one consistent theme is linking Ex-GIS symptomology to IBS, which requires more or clear reasoning, if the authors wish to include it. While the symptoms may be similar, a connection between the two is not supported by the current article. Many of the references could also be updated with newer information. The references also need to be formatted correctly throughout the text. Specific suggestions can be found below by section.

 

Abstract

While the authors do provide information on the potential benefit of physical activity on the GI system, given that the article is focusing on the negative impact of exercise on the GI tract, this is an odd opener and can cause confusion. I would suggest removing the positive impact on the GI system from the opening abstract and leave it in the introduction, where it is explained. 

 

A few details on the pathophysiology i.e. reduced splanchnic blood flow, gastric emptying etc. as well as the specific nutritional strategies would be of value in the abstract. 

 

Introduction

 

Line 26 - add duration to effect of exercise 

 

Cholelithiasis - consider changing to gallstones, as this is more commonly understood.

 

A brief definition or description of Ex-GIS in the introductory paragraphs would be of benefit, including common symptoms.

 

Line 27 - I would be careful about the statement that mild-to-moderate intensity is protective as moderate intensity for long duration (2+ hours) can have a negative effect.

 

Line 31-36 - Statement regarding “endurance exercise” definition requires a reference.

 

Lines 40-54 - I would consider removing this section and replacing it with a better description of Ex-GIS as mentioned above. One to two sentences regarding the factors you are going to discuss in detail should be sufficient here. At present it is an awkward position of a few details, but insufficient information to really be valuable. For instance, stating that exercise results in greater alpha-diversity is likely not valuable unless someone has a solid understanding of the gut microbiota and the effects of alpha-diversity. Better to state that exercise can impact the composition of the gut microbiota - and then discuss in detail in a section below.

 

“In this optical” is used frequently, however, isn’t really a word combination used in English. Consider “in this light” or other.

 

2.1 Neuroendocrine-gastrointestinal

The discussion surrounding gut peptides is of interest, however, additional detail is required. A note on what these hormones do is needed to provide context as to how they may impact Ex-GIS. Stating they have “various peripheral effects” is too vague. 

 

The link between epinephrine and adenosine should also be stated. 

 

Additional references on the impact of exercise on GLP-1 and PYY in humans should be cited i.e. https://pubmed.ncbi.nlm.nih.gov/33831896/

 

The impact of neurotransmitters listed on gut motility etc needs to be described for connections to be made to gastric emptying and gut motility. 

 

In general, while this section is of interest, gut peptides and neurotransmitters are not frequently cited as the main reason for Ex-GIS, so a better case is needed. While they may be a factor, it requires connecting the dots of their role in the body, the impact of exercise on them, and the resulting potential for Ex-GIS and the information in this section is not presented in this manner.

 

Line 134 - what potential “other mechanisms” for diarrhea?

 

2.2 Circulatory-gastrointestinal pathways

Line 149 - reference required for 80% reduction in blood flow.

 

Line 176 - Describe the effects of endotoxemia; what will the translocation of LPS do? What, if any, symptoms will present in the short or long term?

 

Line 185 - Gut microbiome - please expand this section; now would be the time to discuss what is known about diversity and the impact of exercise on the gut microbiome. The information on alpha diversity could be moved to this section if it is explained. Consider https://pubmed.ncbi.nlm.nih.gov/31758610/ and other studies on probiotics and exercise if you wish to include a comment on this here.

 

Line 204 - Please be careful about linking the cause of the symptoms to intestinal damage as studies often find they aren’t linked https://pubmed.ncbi.nlm.nih.gov/35138972/ 

 

Gastrointestinal Symptoms During Exercise

Line 212 - Consider “medical” as opposed to “organic”

 

Line 214 - the term “resistance” is confusing here as the focus is on “endurance” exercise. I would consider removing the sentence altogether.

 

Line 221 - Again the link the authors are intentionally or inadvertently making to IBS is not supported. While the symptoms may be similar in some cases, the reference cited only indicates that in those with IBS exercise may be problematic, but then carries on to indicate that exercise usually improves IBS. I’m not sure why it is relevant to mention that some of the symptoms overlap?

 

Line 247 - Please re-word “on the other hand” as it implies what will follow is in opposition to what was stated previously whereas, both of the statements refer to improvements with gut training.

 

Line 262 - What intensity of cyclists? Recreational vs competitive? Most studies find running more problematic than cycling or no difference if intensity and time are controlled for.

 

Line 263 - While relevant to the manuscript, adding bowel movements, stress and NSAIDs under the symptoms section seems out of place, especially as causes were discussed in the previous pages. Consider an “other causes” paragraph above with environmental, stress, and medications grouped together.

 

Line 268 - 277 - consider removing the section on iron-deficiency, as it isn’t really relevant to the manuscript. While there is the potential for blood loss due to damage to the gut, very few runners report GI bleeding as a symptom and it would be very rare for it to be sufficient to cause iron deficiency. The other factors listed such as plasma volume increase, traumatic haemolysis, sweat loss, and insufficient dietary intakes are much more likely to be the cause of iron deficiency in runners. I would remove this to allow for space for more detail on the content that is core to the manuscript.

 

Line 278 - Again, I would move the section on stress up to the causes area, rather than under the title of symptoms.  

 

The symptoms section would benefit from a brief comment on what factors are more likely to result in symptoms. Cycling vs running is discussed, but age, gender, running experience etc. can all play a role.

 

Nutritional and Behavior Strategies

Fiber and protein are usually mentioned in recommendations to reduce EX-GIS.

 

Caffeine and other supplements such as Sodium Bicarbonate also impact EX-GIS.

 

Efficacy of Specific Diets

Line 367 - Not all studies find improvements in performance with HFD, consider Lousie Burkes work https://pubmed.ncbi.nlm.nih.gov/32358802/

 

Line 374 - The information on gluten not related to athletes can be removed. The information on CD etc. is not relevant here. Focus on the information as it relates to athletes.

 

Conclusion

Line 516 - term “elaborated” doesn’t make sense in this context.

Generally, the English is well done with just a few improvements suggested. 

Author Response

Dear Reviewer,

we would like to thank for your detailed article revision; your suggestions allow us to improve our paper. In the attachment you will find more explanation about varius points required. We also uploaded newer references and we provided to offer our prospective expecially regarding the connection between symptoms and pathogenesis IBS / EX-GIS and other aspect you will find in the integral text.

Kind regards,

The authors.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors, Although the article is well written, it lacks novelty. In addition, it does not meet the minimum standards for publication.

Author Response

Dear reviewer,

thank you for your comment.

In the attachment you will find our answer.  

Kind regards,

The authors.

Author Response File: Author Response.docx

Reviewer 3 Report

Thank you for the opportunity to review this manuscris about  - Exercise-induced gastrointestinal symptoms in endurance 2 sports: pathophysiology, symptoms and nutritional management.

Recommendations>

The abstract must be expanded because it does not highlight the relevant aspects pursued within the content of the manuscript. It recommends expanding the keywords with some relevant ones that have been highlighted

The article must be restructured to comply with the structure imposed by the journal for review.

 

To include the Methods and Materials section and the Discussion section.

 

To include the Prisma diagram or to highlight the selection method of bibliographic references.

Author Response

Dear Reviewer,

we would like to thank you for your article revision.

In the attachment you will find response point by point and the extended sentences we added in the articles, as you suggested.

Kind regards,

The authors.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I have already rejected this article due to poor quality.

Reviewer 3 Report

The authors improved the manuscript according with the recommendations.