Evaluating the Effects of Full-Fat Yogurt Consumption on Circulating Inflammatory Biomarkers and Ex Vivo Peripheral Blood Mononuclear Cell Inflammatory Responses in a Randomized-Controlled Crossover Trial

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Short summary of the manuscript explaining what the study is about

The authors conducted a double-masked, controlled crossover experiment with 13 participants aged 45-75 years. The two, three-week experimental diets comprised three daily servings of full-fat or non-fat yogurt and were each preceded by a one-week run-in diet. Following each diet, circulating inflammatory biomarkers and cytokine concentrations in the supernatants of peripheral blood mononuclear cells under control or lipopolysaccharide-stimulated conditions were measured. Compared with non-fat yogurt intake, circulating immature granulocyte concentrations were lower following full-fat yogurt intake, but there were no other differences in leukocyte concentrations. Circulating concentrations of cytokines or other inflammatory markers did not differ by diet. Cell supernatant interleukin-1β concentrations were lower following the full-fat yogurt diet under unstimulated conditions but were not different between diets under stimulated conditions. There were no differences by diet in supernatant concentrations of other cytokines under unstimulated or stimulated conditions. The authors concluded that minimal differences in inflammatory tone were observed following short-term consumption of three daily servings of full-fat or non-fat yogurt in individuals with prediabetes.

General comments

The manuscript scientifically sound and is the experimental design appropriate. The figures/tables/schemes are appropriate. They properly show the data. The authors used the proper statistical methods. However, it seems necessary to confirm that the group size is sufficient to draw statistical conclusions from the conducted experiment. The conclusions consistent with the evidence and arguments presented.

Minor issues

The title should be written with the first capital letters.

8-13 – The authors’ initials and e-mail addresses should be added.

54 – The systemic inflammatory markers should be listed.

The Introduction should include more information on the fat content and fatty acid composition of the yogurt.

Approximate yogurt composition should be reported in Materials and Methods section.

Description “Value expressed as mean ± SD” should be removed from the table footnotes because Mean and SEM is mentioned in the table head.

Abbreviations of journal title must be with dots (Br. J. Nutr.).

637, 782 – Abbreviation of journal title is needed.

Author Response

Comment 1: The title should be written with the first capital letters.

Response 1: This has been changed (L2-5).

Comment 2: 8-13 – The authors’ initials and e-mail addresses should be added.

Response 2: These have been added (L6-9).

Comment 3: 54 – The systemic inflammatory markers should be listed.

Response 3: This has been added (L57).

Comment 4: The Introduction should include more information on the fat content and fatty acid composition of the yogurt.

Response 4: The citation to our previous manuscripts that include the full fatty acid composition of the yogurt was added to materials and methods (L132-133).

Comment 5: Approximate yogurt composition should be reported in Materials and Methods section.

Response 5: This has been reported in our previous manuscript; thus we have added a note (L132-133).

Comment 6: Description “Value expressed as mean ± SD” should be removed from the table footnotes because Mean and SEM is mentioned in the table head.

Response 6:  These have been removed.

Comment 7: Abbreviations of journal title must be with dots (Br. J. Nutr.).

Response 7:  These have been added.

Comment 8: 637, 782 – Abbreviation of journal title is needed.

Response 8: These have been corrected.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

.This is an important study, as most yogurts sold in supermarkets are very low in fat and full of sugars, justified by being considered healthy. It is important to make this claim evidence-based, and this study does so with an 'exploratory' trial.

Anyway, this reviewer needs some clarifications about the study:

1) How many subjects were randomized? How many randomized subjects did not complete the study?

2) Why were the tests not repeated at the end of the second run in, before the crossover? How was the carryover effect evaluated?

3) If the tests had been performed before the crossover at the end of the second run in (wash out), a simple difference of differences analysis for paired data could have been used. In any case, why was at least a simple paired t-test not performed with the results at the end of the treatments? The analysis with the mixed linear model really has very few subjects to work with.

Author Response

Comment 1: How many subjects were randomized? How many randomized subjects did not complete the study?

Response 1: A total of 15 participants were randomized; 2 participants did not complete the study and were lost to follow-up prior to any experimental endpoints. The full CONSORT diagram has been reported in our previous manuscript; thus we have added a note (L264-265).

Comment 2: Why were the tests not repeated at the end of the second run in, before the crossover? How was the carryover effect evaluated?

Response 2: Carryover effect was evaluated by including the ‘day’ term in the statistical model; this was a proxy for sequence effect. This has been added to the statistical analysis section (L238-239).

Comment 3: If the tests had been performed before the crossover at the end of the second run in (wash out), a simple difference of differences analysis for paired data could have been used. In any case, why was at least a simple paired t-test not performed with the results at the end of the treatments? The analysis with the mixed linear model really has very few subjects to work with.

Response 3: The benefit of using the linear mixed model was so that the covariate could be accounted for, as well as day and sex. This statistical design has been used consistently for this trial (10.1016/j.nutres.2025.02.005; 10.1186/s12944-025-02616-4).

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

This reviewer is not completely satisfied with the Authors' responses to his comments on the design and statistical analysis of this crossover trial. However, he considers the medical significance of the work very important, and therefore he refrains from requesting further details on the statistical nuances of the paper. The reviewer admits that his Diploma in Medical Statistics (Italy) and his PhD in Epidemiology (USA) were obtained a long time ago, so he is not entirely confident about the correctness of his comments.