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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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Reviewer #1: The authors are commended for undertaking and expertly exploring the prevalence of iron deficiency in adolescents and how it relates to dietary habits and iron deficiency. Using a ferritin cutoff of < 15 to define iron deficiency (WHO recommendation)

As much as it can be inferred that a diet low in meat in addition to HMB can lead to greater iron deficiency, it is helpful to have this data and also apply the SAMANTA questionnaire.

Although there are recommendations to consume less meat for health/ethical reasons, this study raises the questions about how such recommendations can impact a cohort of adolescents at risk for iron deficiency.

Reviewer #2: Whilst the full dataset is not provided, a statement is made that it is accessible with caveats.

Title: Is ‘Iron insight’ needed at the beginning of the title?

General points:

This paper addresses an important area of health and a widely studied topic.

Good size cohort (n=394), from two schools.

Simple cross sectional study design describing prevalence and then Odds ratios calculated for iron deficiency by group and combined.

Findings not particularly novel but confirmatory of what has been reported elsewhere.

Very well written article with an excellent overview of the literature.

The article seems very similar to this article recently published where ferritin levels were reported according to diet types: Stubbendorff, A., Borgström Bolmsjö, B., Bejersten, T. et al. Iron insight: exploring dietary patterns and iron deficiency among teenage girls in Sweden. Eur J Nutr 64, 107 (2025). https://doi.org/10.1007/s00394-025-03630-z

The authors need to cite this article and make it clear how the present article is different.

I see that this is explained line 112-114, however, some further explanation would be welcomed, perhaps in the discussion.

Can the authors comment on how representative these school children are of the general population? i.e. the socio-demographic status?

I would recommend supplying the full questionnaires used, including the translations, as supplementary files.

Were samples transported to a laboratory or analysed onsite?

Please check the following statement, line 114:

“Those with anemia (Hb <107 g/L as per local reference values) or ferritin >150 μg/L were referred to their primary care center for follow-up.”

Should this be ferritin < 15 ug/L? If it is a threshold for iron overload, please provide an explanation.

Figure 2 typo: ’stainig’

Line 160-163 and Fig S1

Please explain how the DAG was constructed - what sources of information were used?

On the DAG figure itself, or caption, please provide more information, e.g. an explanation for the colours of the arrows.

Discussion

LIne 288-291. I am somewhat concerned about the suggestion of increasing use of iron replacement therapy, tranexamic acid or hormonal contraceptives in this young population. These come with their own risks and this must be acknowledged here. A decision would need to be made - which one carries a higher health risk? HC use in particular could be counter-productive as it removes the natural health signal of menstruation which has been termed a ‘vital sign’, and carries other health risks. This needs a fuller explanation or should be removed. At the very least non-pharmacological interventions should be considered/attempted first in these young females.

Line 350: There is substantial evidence that menstruating females require more iron than males due to menstrual blood losses. Therefore I would suggest that a lower cutoff for females doesn’t lack scientific evidence, in fact it runs counter to the scientific evidence.

Reviewer #3: Dear Editor, Dear Authors,

Thank you for the opportunity to review the manuscript titled: “Iron insight - Exploring the effect of menstrual loss and dietary iron intake on iron deficiency in teenagers: a cross-sectional study”. The results of this study identify the important problem of iron deficiency of adolescent girls. The manuscript is well written, however I have a few questions and suggestions:

1. The title of the study states, that it “explores dietary iron intake”, however from what I understand from the methods section, this particular manuscript is based on participant self-report of meat restriction diet. There is no information on dietary assessment methods used, therefore we do not know what is the dietary iron intake among the participants. As described in the discussion, the intake of iron itself could be within dietary recommendations, however combining dietary factors, such as consuming vitamin C, phytates, or casein could influence the absorption.

2. There is no information on the toxicity of supplemental iron, which I would recommend to add in the discussion. Are there any food products mandatory fortified with iron in Sweden?

3. For future consideration, it would be interesting to collect information on physical activity of the participants; regular physical activity seem to reduce risk of menstruation irregularities, including the heavy menstrual bleeding.

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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<p>Exploring the effect of menstrual loss and dietary iron intake on iron deficiency in teenagers: a cross-sectional study

PONE-D-25-27936R1

Dear Dr. Söderman

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Krzysztof Durkalec-Michalski, Ph.D

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions??>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: (No Response)

Reviewer #3: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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Reviewer #1: I appreciate that the authors have taken the time to address the concerns that I had initially and should be commended. Thank you very much.

Reviewer #2: I am satisfied that the reviewer comments have been satisfactorily addressed and I have no further comments.

Reviewer #3: Thank you for thoroughly adressing all the comments! Here are some studies which analyse the association between HMB and physical activity: doi: 10.3390/healthcare12192005; doi: 10.1093/humrep/deab055. Sweden has interesting history of iron fortification: doi: 10.1093/humrep/deab055.

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what does this mean? ). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy

Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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