The Dose Response Effects of Partially Hydrolyzed Guar Gum on Gut Microbiome of Healthy Adults

Round 1

Reviewer 1 Report (Previous Reviewer 1)

I believe that this manuscript has been sufficiently revised and recommend it for publication directly

Author Response

Thank you for reviewing our paper.  We appreciate your effort.

Joanne Slavin

Reviewer 2 Report (Previous Reviewer 2)

Author Response

Thank you for your review and suggestions.  We appreciate your hard work.

Joanne Slavin

Reviewer 3 Report (Previous Reviewer 3)

Unfortunately, the author did not fully answer our suggestions.

Author Response

Thank you for your suggestions to provide additional information on the analytical methods used to measure the microbiota in this study.  We appreciate that methods to measure gut microbes continue to evolve and it is difficult to compare results across studies when methods have evolved.  We have revised the manuscript to address these challenges.  We have also clearly stated that this is not the definitive study on PHGG and changes in the gut environment including other metabolites are needed in future studies.

Round 2

Reviewer 3 Report (Previous Reviewer 3)

The authors demonstrated the changes in gut microbiota by the treatment with PHGG in human. To improve the quality of this paper, the authors should revise it according to the following suggestions;

The analysis of the gut microbiota in this study was extremely insufficient, and the overall picture of the gut microbiota cannot be seen. First, please show the changes in α-diversity and β-diversity of the  gut microbiota. Furthermore, use software such as QIIME to analyze  gut microbiota changes after administration of PHGG.

Author Response

We have provided all the information we have on changes to the gut microbiota with consumption of 0, 5, and 10 grams of PHGG in healthy human subjects.  We do not have information changes in alpha-deversity and beta-diversity with this data set.  We also cannot use softward such as QIIME to analyze gut microbiota changes after administration of PHGG.  

We have edited the paper to include limitations on our data and suggestions that future work should include these suggestions.

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

This study conducted a randomized, double-blind, placebo-controlled trial using PHGG, showing that PHGG can regulate intestinal microorganisms and increase the content of beneficial microorganisms.

But there are problems with the manuscript as follows:

Please check whether the reference marking method in the manuscript meets the requirements of the journal.

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Line-29, Need to add references.

Line-148, 2.516. S rRNA should be modified to 2.5. 16S rRNA.

Author Response

Thank you for your suggestions.  Reference on line 29 has been added.

Line 148, correction has been made as suggested.

Reviewer 2 Report

In this work, the authors evaluate changes in the gut microbiome in response to PHGG supplementation among  healthy individuals in randomized, placebo-controlled, double-blind dietary intervention  study.

The manuscript deals with a topic of great relevance and potential interest for the scientific community and health-care providers. It is also well written and propoerly structured. But In my opinion, the manuscript requires some modifications and, therefore, I am reporting my suggestions below.

1.      How the sample size was estimated? Is study population was representative?

2.      The study included subject with BMI of >18.5 and <30 kg/m2; therefore, people with excessive body weight (overweight) could also participate in the study. How this fact, could affect the final results? If the other parameters as waist circumference or body fat composition were also estimated to exclude subjects with abdominal obesity or meabolically-obese normal weight subjects?

3.      The aim of the study is clearly defined as “to explore the effects of 2 weeks supplementation of low-dose PHGG on the gut microbiome of healthy individuals in comparison with a low-fiber diet”. But, in section 2.6 and 2.7 appeared additional outcomes (cortisol level and self-assessement of stool type using Bristol Stool Form Scale (BSFS) visually). Please provide additional information to the Introduction to justify and explain the background for these elements.

4.      Line 49 and line 52 -> please change (5,6,7) to (5-7) , (8, 9, 10, 11, 12) to (8-12) and throught entire manuscript

5.      Line 75 -> double „in the study” – Please correct it.

6. the presence of dots and offsets impairs the readability of the tables

Author Response

1. The sample size was calculated on pilot data for changes in microbiota with PHGG.  We included healthy subjects, both men and women, as required by our IRB.
2. We recruited subjects with BMI between 18.5 to 30, but the average BMI of subjects was 25.  No subjects with abdominal obesity or metabolically-obese normal weight subjects were included.
3. Our primary endpoint was change in microbiota with low doses of PHGG.  Secondary endpoints were stool weight, stool consistency, Bristol Stool Form Scale assessed by the investigators, and cortisol level.  We have given additional information to justify and explain the background for these endpoints.
4. The references have been revised as suggested.
5. Line 75 has been corrected.
6. We agree on the readability of the tables and would appreciate the help of the editors to improve their readability. 

Reviewer 3 Report

The authors evaluated changes in the gut microbiome composition of healthy individuals in response to low-dose PHGG supplementation compared with a low fiber diet, and demonstrated that supplementation with low doses of PHGG has the potential to cause shifts in gut microbiome composition. To improve the quality of this paper, the authors should revise it according to the following suggestions,

1) It only shows the changes in abundance of a specific type of gut microbiota, but does not give us a comprehensive picture of gut microbiota. It is better to consult an expert on this area for analysis. Information on alpha diversity and beta diversity is also essential.

2) Although much data has been reported on the effects of PHGG on the gut microbiota, there are many differences in their results. Discussion on this point is essential.

3) Changes in gut microbiota alone are not sufficient; information on metabolites, especially short-chain fatty acids, is essential.

Author Response

Thank you for your review.

1. We agree on your comment.  Our primary aim of the study was to determine if small doses of PHGG would alter the gut microbiota.  The advantage of the design is that it was a double blind RCT where the subjects consumed the treatments in a randomized design.  So each subject consumed the fiber-free treatment, and the 2 small doses, 3 and 6 grams of PHGG.  We don't have findings on alpha diversity or beta diversity with our analyses.  So our major finding is that small doses of PHGG can alter the microbiota and we share all of our results in the paper.  We agree that methods to measure changes in microbiota continue to evolve and our results add to the body of data on interventions with dietary fiber and changes in the gut microbiota.  The literature is especially low on dose responses with fiber and our results show that dose of fiber does not change the microbiota response in a predicatable fashion.
2. We agree that other work with PHGG shows differences in effect on the gut microbiota.  Other work supports that PHGG is a prebiotic since it increases bifidobacteria or lactobacillus.  We have added a section to the discussion of the paper as you suggested.
3. We agree that data on short chain fatty acids would add to our work and we collected fecal samples from each treatment for measurement of SCFA.  Our past work with SCFAs questions whether fecal levels of SCFAs are relevant as most SCFAs are absorbed along the colon so fecal samples give little signal on SCFA production throughout the colon.  We have not incuded our SCFAs results in this paper as we found no differences in SCFAs across the 3 treatments.  Our work in in vitro systems finds that PHGG does increase production of SCFAs.  And that it is a prebiotic as measured in in vitro systems.  So we agree that metabolites of fermentation are essential in determining the effects of fiber fermentation, we want to keep our focus of this paper on the microbiota changes we found with small doses of PHGG.