Vitamin D Fortification Strategies and Policy Landscape in Selected European Countries

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is a good review of the fortification of Vitamin D in different regions of Europe- whether they are voluntary or mandatory and the associated evidence to say whether or not such fortification is effective. A case for harmonisation in terms of mandatory fortification is presented. The paper is written well. The tables can be better presented with countries mandatorily fortifying followed by voluntary fortification and the monitoring and surveillance in place in each region could have been better explained. The paper can be further proof-read to take care of minor edits in language. Otherwise this is a good review pulled together in one place for explaining the European scene to readers.

Comments on the Quality of English Language

Minor errors and edits in English language needs revision.

Author Response

Dear Editor-in-Chief,

Dear Reviewers,

 

We would like to submit the revised manuscript entitled: “Vitamin D fortification strategies and policy landscape in selected European countries” for publication in Nutrients (Special Issue Mega-Trend: Sustainable Nutrition and Human Health).

The main text has been updated and the revision has been made according to the suggestions of the Reviewers. The authors would like to thank the Reviewers for valuable comments, which helped to improve the quality                        of the manuscript.

Please find below a detailed point-by-point response to all comments.

Sincerely yours,

Corresponding author

 

Rev. 1.

We would like to sincerely thank you for your advices and constructive comments.

Comment: The tables can be better presented with countries mandatorily fortifying followed by voluntary fortification and the monitoring and surveillance in place in each region could have been better explained.

Reply: The tables have been reorganized to list countries with mandatory fortification first, followed by those with voluntary fortification. Monitoring and surveillance are now described in a separate subsection, Monitoring and Oversight of Large-Scale Food Fortification (LSFF) Programs, which includes details on the type of fortification (mandatory vs. voluntary) and specific country examples. Additionally, Figure 2, illustrating the LSFF policy cycle for vitamin D fortification, has been included.

 

Comment: The paper can be further proof-read to take care of minor edits in language.

Reply: done.

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a valuable and timely contribution to the field of nutritional policy research. The systematic compilation of food-based dietary guidelines (FBDG) across multiple European countries regarding vitamin D policy represents an important resource for policymakers, researchers, and public health professionals. The comprehensive approach to analyzing vitamin D recommendations, fortification practices, and policy variations across diverse European contexts demonstrates scholarly rigor and addresses a significant gap in the literature, particularly given the widespread prevalence of vitamin D deficiency in European populations.

Abstract:

1. The abstract should clearly state the number of countries analyzed and the time period covered by the FBDG review. Specify whether this includes all EU member states or a selected subset, and provide justification for any exclusions.

Introduction:

1. Strengthen the rationale by including recent epidemiological data on vitamin D deficiency prevalence across different European regions. The introduction should explicitly state the research questions or objectives that guided this narrative review.

Results Section:

1. The presentation in Table A1 (Appendix A) is comprehensive, but the main text should include a synthesized analysis. Consider organizing results by themes such as: (a) countries with mandatory fortification policies, (b) countries with voluntary fortification, (c) countries relying primarily on supplementation recommendations, and (d) countries with no specific vitamin D policy.
2. Include quantitative summaries where possible. For example: "X out of Y countries (Z%) recommend vitamin D supplementation for specific population groups" or "Only X countries have implemented mandatory fortification programs." This provides readers with quick insights into policy patterns.

Discussion Section:

1. Expand the discussion on geographical and climatic factors influencing vitamin D policy differences. Reference61 mentions Southern European countries - discuss why these regions, despite higher sun exposure, still face vitamin D deficiency challenges and how this influences their FBDG approaches.
2. Based on references 54, 56, and 57, dedicate a subsection to discussing the practical challenges of food fortification implementation. Address regulatory barriers, industry compliance, consumer acceptance, and cost-effectiveness considerations that may explain policy variations across countries.
3. Include a critical discussion on the feasibility and desirability of harmonizing vitamin D policies across Europe. Consider the European Food Safety Authority (EFSA) recommendations and discuss why individual countries may deviate from these guidelines.

Author Response

Thank you for your valuable comments and detailed analysis of our work.

Comment: Abstract: The abstract should clearly state the number of countries analyzed and the time period covered by the FBDG review. Specify whether this includes all EU member states or a selected subset, and provide justification for any exclusions.

Reply: In response to the reviewer’s suggestion, we have clarified in both the abstract and Methods section the number of countries analyzed and the time period covered. This review now includes all European Union (EU) Member States (n = 27), European Free Trade Association (EFTA) countries (n = 4), and the United Kingdom. These countries were included due to their substantial alignment with EU legislation in recommendations or regulatory frameworks. For EU Member States, the framework established by Regulation (EC) No 1925/2006 was examined alongside national implementation measures. For EFTA countries and the UK, corresponding national legislation and regulatory guidance were reviewed.

 

Comment: Introduction: Strengthen the rationale by including recent epidemiological data on vitamin D deficiency prevalence across different European regions. The introduction should explicitly state the research questions or objectives that guided this narrative review.

Reply: we have strengthened the rationale in the Introduction by highlighting recent epidemiological data on vitamin D deficiency. Specifically, we now reference the global analysis of 7.9 million participants from 308 studies, covering the period 2000–2022 (Cui et al., 2023), which provides the most up-to-date prevalence estimates. In addition, we have incorporated data based on standardized datasets to illustrate deficiency patterns across specific European regions. The Introduction also now clearly states the research objectives.

 

Comment: Results: The presentation in Table S1 (Appendix S) is comprehensive, but the main text should include a synthesized analysis. Consider organizing results by themes such as: (a) countries with mandatory fortification policies, (b) countries with voluntary fortification, (c) countries relying primarily on supplementation recommendations, and (d) countries with no specific vitamin D policy.

Reply: Following the reviewer’s suggestions, the Results now consistently refer to Table S1, which provides a comprehensive overview of FBDGs in individual countries and highlights that differences in national guidelines reflect variation in institutional frameworks and formal policy contexts supporting vitamin D fortification initiatives. We have maintained a geographic organization, presenting countries by Northern, Western, Central, and Southern Europe, to capture similarities in latitude, sun exposure, dietary habits, and food availability, which influence the context and effectiveness of vitamin D fortification strategies and allow meaningful comparisons across countries with similar population-level risk factors. Additionally, to provide a clear visual distinction of different fortification approaches across Europe, we have added a map (Figure 1. Vitamin D fortification policies across European countries).

 

Comment: Results: Include quantitative summaries where possible. For example: "X out of Y countries (Z%) recommend vitamin D supplementation for specific population groups" or "Only X countries have implemented mandatory fortification programs." This provides readers with quick insights into policy patterns.

Reply: In the Results, we highlighted that mandatory vitamin D fortification is relatively rare in Europe, applying to only a few countries, while in the remaining states fortification is voluntary or absent. In line with the reviewer’s suggestion, we included quantitative data: “With respect to fortification policies (Tables 1–4), only four out of 32 (12.5%) countries analyzed (Finland, Sweden, Belgium, and Poland) have implemented mandatory vita-min D fortification for at least some foods”. Quantitative data on vitamin D supplementation were not included, as recommendations from professional bodies or health authorities do not always constitute formal public health policy, and comparable, systematic information on population-level implementation across all EU, EFTA, and UK countries is limited.

 

Comment: Discussion: Expand the discussion on geographical and climatic factors influencing vitamin D policy differences. Reference 61 mentions Southern European countries - discuss why these regions, despite higher sun exposure, still face vitamin D deficiency challenges and how this influences their FBDG approaches.

Reply: Following the reviewer’s suggestion, we expanded the Discussion to provide a more detailed explanation of geographical, climatic, and behavioural factors contributing to vitamin D deficiency in Southern Europe. We highlighted the “Mediterranean paradox,” emphasizing that despite high sunlight availability, effective cutaneous vitamin D synthesis is limited by indoor living, clothing, sunscreen use, urbanisation, sedentary lifestyles, high ambient temperatures, and seasonal variation. We also addressed age-related vulnerability and the impact of dietary westernization, particularly among younger populations, which reduces intake of vitamin D-rich traditional foods. Furthermore, we clarified how these factors intersect with FBDG approaches, noting that Southern European guidelines generally address vitamin D only indirectly and lack explicit recommendations for supplementation or fortified foods, in contrast to higher-latitude countries such as Finland or Sweden (Appendix A, Table A1). This contextualization strengthens the rationale for region-specific nutrition policies and public health strategies.

 

Comment: Discussion: Based on references 54, 56, and 57, dedicate a subsection to discussing the practical challenges of food fortification implementation. Address regulatory barriers, industry compliance, consumer acceptance, and cost-effectiveness considerations that may explain policy variations across countries.

Reply: Following the reviewer’s suggestion, we added a dedicated subsection in the Discussion (4.1) addressing practical challenges in implementing vitamin D food fortification policies. We highlighted regulatory, industrial, economic, and population-level barriers, including variations in governance frameworks, industry capacity, consumer acceptance, cost-effectiveness, and monitoring infrastructure. Country-specific examples from Belgium, Romania, and Slovenia illustrated how these challenges affected the real-world implementation and effectiveness of fortification strategies. We also emphasized that differences in interpretation of EFSA dietary reference values, combined with limited or heterogeneous population data, contributed to the variability in national policy design across Europe. To provide a clear and structured overview, we included a summary table (Table 5) outlining these practical challenges and their implications for policy design. References 54, 56, and 57 have been renumbered as 32, 33, and 34.

 

Comment: Include a critical discussion on the feasibility and desirability of harmonizing vitamin D policies across Europe. Consider the European Food Safety Authority (EFSA) recommendations and discuss why individual countries may deviate from these guidelines.

Reply: We expanded the Discussion in subsection 4.1 (Practical challenges in implementing vitamin D food fortification policies) to include a critical consideration of the feasibility and desirability of harmonizing vitamin D policies across Europe. We clarified the role of EFSA DRVs as a common scientific reference while emphasizing that they are not legally binding. We also elaborated on key factors - such as differences in regulatory frameworks, dietary patterns, sun exposure, and population risk profiles - that limit the feasibility of a uniform approach and explain why countries may diverge from EFSA guidance. This addition provides a more nuanced perspective on policy variation and the need for context-specific strategies.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript addresses an important issue in nutrient deficiency at the population level worldwide, i.e., policies designed to ensure food fortification with vitamin D in different regions of Europe. The text is well-written and clearly approaches the research conducted by the authors; therefore, the suggestions described below are intended to increase the interest of the manuscript to a wider global audience:

[1] The Introduction presents well-connected arguments on vitamin D deficiency and food fortification; however, the second and third paragraphs are quite long and could be separated into four and two paragraphs, respectively: the second paragraph could focus on vitamin D sources (lines 51-56), whereas the following sentences could be divided into three paragraphs (methods for assessment of vitamin D status - lines 56-62; definition of population groups vulnerable to vitamin D deficiency - lines 62-67; and effectiveness of food fortification - lines 67-72); and the third paragraph could be separated into two paragraphs (vitamin D policies in Europe - lines 73-78; and the definition of the focus of the study - lines 78-85);

[2] Authors could consider including additional literature on vitamin D deficiency in other countries (American, Asian, African, etc.) to increase interest from readers in other continents, who may use the framework proposed to map vitamin D fortification policies in other parts of the world;

[3] The Methods section is generally well-described, but I suggest either including a table in the section or in the supplementary materials to show the keywords used during the search for the identification of documents on fortification policies in different national languages (lines 94-98);

[4] The list of variables extracted from the documents could be presented in a bullet list, instead of within the paragraph (lines 105-109);

[5] The targeted searches of literature on "micronutrient fortification policies and population vitamin D status" (lines 115-119), although used to support the interpretation of policies, should be accompanied of more detailed description (e.g., peer-reviewed literature concerning any country? or only focusing on European countries? which keywords and inclusion/exclusion criteria supported the selection of studies?);

[6] The results of the study are quite interesting, and my recommendation is to include colored maps to identify/point the main policy strategies on food fortification (e.g., one map showing with different colors the existence or absence of mandatory/market-driven policies, and one map presenting the main food groups adopted in fortification);

[7] The Discussion and the Conclusion are well-written and clear; yet, the Discussion lacks the description of contributions and limitations of the study, in addition to suggestions for advances in terms of policy. The Conclusion could further explore potential research agendas for the future. Potential policy implications and suggestions (e.g., possibility of convergence and/or standards on vitamin D fortification policies among countries), and further research on the subject could address the absence of fortification patterns among European countries.

Author Response

Thank you for your valuable comments and detailed analysis of our work. 

Comment: The Introduction presents well-connected arguments on vitamin D deficiency and food fortification; however, the second and third paragraphs are quite long and could be separated into four and two paragraphs, respectively: the second paragraph could focus on vitamin D sources (lines 51-56), whereas the following sentences could be divided into three paragraphs (methods for assessment of vitamin D status - lines 56-62; definition of population groups vulnerable to vitamin D deficiency - lines 62-67; and effectiveness of food fortification - lines 67-72); and the third paragraph could be separated into two paragraphs (vitamin D policies in Europe - lines 73-78; and the definition of the focus of the study - lines 78-85).

Reply: We have reorganized the Introduction as suggested: the second paragraph has been split into shorter sections on vitamin D sources, assessment methods, vulnerable population groups, and fortification effectiveness. The third paragraph has been divided into two parts covering European policies and the study focus. Additionally, we have incorporated global data on vitamin D deficiency to provide broader context (see next reply).

 

Comment: Authors could consider including additional literature on vitamin D deficiency in other countries (American, Asian, African, etc.) to increase interest from readers in other continents, who may use the framework proposed to map vitamin D fortification policies in other parts of the world.

Reply: We have addressed the reviewer’s suggestion by expanding the Introduction to include additional literature on vitamin D status in regions outside Europe. We now briefly summarize deficiency and insufficiency prevalence in the Middle East, parts of Asia (e.g., India and China), North America, Canada, and African populations, highlighting factors such as fortification practices, supplement use, cultural habits, and skin pigmentation that influence serum 25(OH)D levels. These additions provide a global context while maintaining the focus on Europe, enabling readers from other continents to relate to the framework for mapping vitamin D fortification policies.

 

Comment: The Methods section is generally well-described, but I suggest either including a table in the section or in the supplementary materials to show the keywords used during the search for the identification of documents on fortification policies in different national languages (lines 94-98).

Reply: We thank the Reviewer for this helpful suggestion. To improve transparency and reproducibility, we added a supplementary table presenting examples of the search terms used to identify national fortification-policy documents in English and relevant national languages (Appendix A, Table A2). We also clarified in the Methods that national-language terms were generated using publicly available translation tools and cross-checked against terminology used on official national authority websites.

 

Comment: The list of variables extracted from the documents could be presented in a bullet list, instead of within the paragraph (lines 105-109).

Reply: Thank you for this valuable comment. In response, the list of variables extracted from the regulatory documents has been reformatted into a bullet list in the Methods section to improve clarity and readability.

 

Comment: The targeted searches of literature on "micronutrient fortification policies and population vitamin D status" (lines 115-119), although used to support the interpretation of policies, should be accompanied of more detailed description (e.g., peer-reviewed literature concerning any country? or only focusing on European countries? which keywords and inclusion/exclusion criteria supported the selection of studies?).

Reply: We agree and have expanded the description of the targeted literature search in the Methods section. We now specify that this secondary search was conducted in PubMed and Scopus, focused primarily on European countries, and was used only to contextualize and interpret the regulatory findings rather than to identify the legal basis of national policies. We also added the main search concepts and clarified the eligibility criteria, including the exclusion of non-official, commercial, duplicate, and policy-irrelevant sources.

 

Comment: The results of the study are quite interesting, and my recommendation is to include colored maps to identify/point the main policy strategies on food fortification (e.g., one map showing with different colors the existence or absence of mandatory/market-driven policies, and one map presenting the main food groups adopted in fortification).

Reply: To provide a clear visual distinction of different fortification approaches across Europe, we have added a map (Figure 1. Vitamin D fortification policies across European countries), which highlights the presence of mandatory versus voluntary/market-driven policies and includes a list of products fortified mandatorily. Regarding the suggestion for a second map showing all fortified food groups, the authors consider that such a map would be potentially misleading and difficult to interpret because the data are incomplete, heterogeneous, and market-driven fortification practices are not fully documented. Instead, we have emphasized in the text, with appropriate citations, that in most Central, Western, and Southern European countries, fortification is primarily concentrated in margarines, breakfast cereals, selected dairy products, and plant-based beverages. We believe that this textual description, combined with the map of mandatory fortification, provides a clear and accurate overview of the European situation.

 

Comment: The Discussion and the Conclusion are well-written and clear; yet, the Discussion lacks the description of contributions and limitations of the study, in addition to suggestions for advances in terms of policy. The Conclusion could further explore potential research agendas for the future. Potential policy implications and suggestions (e.g., possibility of convergence and/or standards on vitamin D fortification policies among countries), and further research on the subject could address the absence of fortification patterns among European countries.

Reply: The Discussion has been revised to include study limitations (Section 4.4). In addition, the Conclusions section has been expanded and retitled “Conclusions and future perspectives” (Section 6). These revisions address the reviewer’s comment by incorporating policy implications and outlining future perspectives, including the role of monitoring and evaluation systems, population-based studies, and modeling approaches. We also emphasize the need to improve data availability, strengthen public awareness, and support more coordinated strategies across Europe, while acknowledging country-specific differences.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

yes