PONE-D-19-24477

From carbohydrates to fat: Trends in food intake among Swedish nutrition students from 2002 to 2017

PLOS ONE

Dear Dr Bergström,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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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?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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

Reviewer #1: No

Reviewer #2: Yes

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

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The paper by Bergström and colleagues provides insights into dietary trends over an 8 year period in Sweden among female nutrition students. While the sampling of this population is not representative of the Swedish population, the study is unique in that it tracks a subgroup of the Swedish population over time. The authors have done a nice job of placing these findings into the broader nutritional/dietary context in Sweden. While the results are interesting, their presentation could be strengthened through the inclusion of additional methodological details. The study could also benefit from further details on the type of carbohydrates that are being consumed over time such as refined grains versus whole grains.

Specific Comments:

1. The title, abstract (line 24) and discussion (line 319-320) highlight that study time period as being 2002 to 2017; however, the study focuses the analysis on the time period of 2009 to 2017. These sections of the manuscript should be changed to reflect that the main analysis is done using data from 2009 and 2017 and the methodology section can include the details on the full study period.

2. Line 40: change “begun” to “began”

3. The study that is referenced in the introduction from lines 74 to 83 was described at line 74 as a “25-year long cross-sectional study.” Was this a series of cross-sectional studies conducted at different time points within that time frame, a rolling study that continuously collected information on participants, or were participants tracked over time? Additional clarity on the type of study being described would be helpful.

• Further, at line 77, it states that “…in the beginning of the intervention program…” Was there an interventional aspect to this study? Again, more precision on the design of the study being described would be helpful to the reader.

4. I’d suggest editing the sentence at line 112 to the following “The association of overweight and obesity with chronic diseases, e.g. type 2 diabetes, high blood pressure, cardiovascular disease, asthma and arthritis, is well established. Diet can affect the development of chronic diseases, either directly or mediated through the development of overweight and obesity, and thus warrants close monitoring in the general population.”

5. It should be clearly stated in the study design section that this was a series of cross-sectional studies.

6. The figures at the end of the manuscript are not labeled with their numbers.

7. Lien 146: Are the results the average of each individuals average 2 day intake? This should be stated in the methods.

8. Line 154: Include a sensitivity analysis with the male participants. Is there any reason to believe that their dietary results would be so different that it would obscure the trends seen in women?

9. Line 157: The characteristics of the excluded participants should be provided along with some information as to whether most of those excluded under- or over-reported calorie intake relative to requirements. Also, since you are just reporting the mean intake, rather than doing any type of regression analysis, you could also include all of the values and report the median, which will not be influenced by extreme outliers.

10. Table 1: The line that only includes the value of 729 is not easy to understand. I’d exclude this line from table 1.

11. Lines 188 to 191: more explanation on how the percent of energy from fiber was calculated. What value in kcal/g was used as the energy density for fiber? Was the same value used for all types of fiber i.e. soluble and insoluble? Was 4kcal/g used as the energy density of carbohydrates and protein and 9 kcal/g for fat? This information should also be included in the methodology section.

12. Was the height and weight information in Table 1 self-reported? How this information was collected should be included in the methodology section and this limitation should be noted in the discussion section.

13. Line 207: change “follow” to “followed”

14. Figure 2: More methodological details on the data from the Swedish Board of Agriculture and the Swedish National Food Agency should be included in the methods section.

15. Table 2: Report the p value rather than just “<0.01”

16. Line 279: It was noted that there was not a statistically significant difference in SFA intake over the time period but the authors didn’t note that there was a statistically significant trend. This should be included in the results.

17. The rationale for reporting only vitamin D, folate, iron, potassium and sodium, and not other nutrients should be included in the methods section.

18. Starting after page 8, the page number does not continue sequentially.

19. Line 288: your statistical test is to determine if there is greater variability between the years rather than within each year – it doesn’t test specifically to see if there was an increase during the time period.

20. Lines 283 to 300: Note in the description of the results in this section that comparisons to national averages were descriptive only and statistical analyses weren’t done.

21. Table 3: include the SD or SE in the table for each year.

22. Line 356: it was noted that reporting food intake was a mandatory component of the course yet the response rate was still only 66% for women? Was this due to lost data or to the participants not submitting the assignment? Additional explanation would be helpful in the discussion.

23. The main findings of the study are that carbohydrate intake has decreased over time among this group. It would be helpful to understand how refined grain and whole grain intake also changed during this time period. Many national dietary guidelines recommend the consumption of whole grains; therefore, it would be helpful to understand if the proportion of refined grains to whole grains changed during this period.

24. Line 376: It should be noted in this paragraph that the percentage of energy from saturated fat increased which is not congruent with most authoritative dietary guidances.

Reviewer #2: This research is of interest . The paper needs of some suggestions :

In Introduction the authors should underline the linkahe between Food consumption data and Food Composition data and adding related references such as: Durazzo et al. Food Groups and Individual Foods: Nutritional Attributes and Dietary Importance.In book: Reference Module in Food Science

DOI: 10.1016/B978-0-08-100596-5.21337-1.

In Material and Methods a scheme of design of study should be added. In subparagraph "Energy intake from protein, fat, carbohydrates, fiber and alcohol 2002-2017", at lines 179-181 the authors should underline the importance of a common language of database in order to allow an exchange/ a comparison of data as well as the study of dish preparation in national database. In this regard proper references should be added such as :Durazzo et al. 2019 Nutritional composition and dietary intake of composite dishes traditionally consumed in Italy. Journal of Food Composition and Analysis.Journal of Food Composition and Analysis 77 DOI: 10.1016/j.jfca.2019.01.007; Durazzo et al. 2019; Italian composite dishes: description and classification by LanguaL™ and FoodEx2. 2019 European Food Research and Technology; Marconi et al. 2018. Food Composition Databases: Considerations about Complex Food Matrices.Foods. 2018 7(1). pii: E2. doi: 10.3390/foods7010002. In subparagraph "Statistical analysis of nutrient intake and food categories" The authors should mention the importance of choice of food groups and variability along databases.

A subparagraph Conclusion should be added.

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Reviewer #1: Yes: Jessica Smith

Reviewer #2: No

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From carbohydrates to fat: Trends in food intake among Swedish nutrition students from 2002 to 2017

PONE-D-19-24477R1

Dear Dr. Bergström,

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

Within one week, you will receive an e-mail containing information on the amendments required prior to publication. When all required modifications have been addressed, you will receive a formal acceptance letter and your manuscript will proceed to our production department and be scheduled for publication.

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Jose M. Moran

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

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

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: (No Response)

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

Reviewer #1: Yes

Reviewer #2: (No Response)

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

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: (No Response)

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

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: (No Response)

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: (No Response)

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7. PLOS authors have the option to publish the peer review history of their article (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