Hello Jason, thank you very much for your comment and for taking the time to analyze the article in such detail.

The article was carried out in an exploratory and generalized way with the aim of determining which foods with vitamin D could be implemented in large-scale ASRS such as the one that could be generated by the injection of 150 Tg of soot into the atmosphere due to a nuclear war. However, the research focused on the comparison of these foods and not precisely on the discussion about the regions of the world that would be really affected by this phenomenon.

Vitamin D is produced naturally by the body when the skin is exposed to UVB radiation from the sun, which under normal circumstances would be a simple and efficient strategy to avoid deficiency. However, Pham et al. (2022) suggest that in a large-scale ASRS, where the amount of available solar radiation could decrease, this solution would not be sufficient. In particular, UVB radiation, which is key for the synthesis of vitamin D, could be especially affected due to the dispersion of aerosols in the atmosphere that could block part of the light that arrives naturally.

The risk would not be homogeneous throughout the world. As you point out, in regions close to the equator, where UVB radiation levels are naturally higher, people could compensate for the lack of light with greater exposure since the climatic conditions do not represent a negative effect on health. However, in areas further from the equator, such as colder regions with fewer hours of light, this solution would not be so viable. In these cases, depending on sun exposure for vitamin D synthesis would be insufficient, especially in winter, which would make it necessary to resort to fortified foods or vitamin D supplements as a prior strategy.

You also raise an interesting point about the scenario in which, instead of being reduced, ultraviolet radiation increases due to the destruction of the ozone layer. This would be a complex problem, although theoretically there could be enough UV radiation to produce vitamin D, prolonged exposure would be dangerous due to the risk of skin cancer and other problems arising from overexposure to radiation. In this scenario, vitamin D supplementation or food fortification would still be the safest option, as reducing sun exposure time would be essential.
Vitamin D deficiency in an ASRS will likely vary by geography and the magnitude of atmospheric changes. While in some regions people could compensate with increased sun exposure, in others this would not be feasible, making food fortification and supplementation play a key role.

For this reason, I think that researching foods with vitamin D would not generate generalized solutions, but would propose solutions of high interest for regions that would be seriously affected by such a scenario.

I appreciate your comments again and I recognize that you mention aspects that would greatly enrich the study :).

Hi Milan, I hope you are doing well.
As you mention, Pham et al. (2022) conclude that, in the event of an ASRS, there would be a shortage of foods capable of providing vitamins E, K and D. However, for the purposes of this project, it was decided to focus on vitamin D for some reasons. First, vitamin D is important for human health, as it plays a fundamental role in calcium regulation and bone maintenance. Although deficiencies in vitamins E and K also have consequences, such as coagulation problems (vitamin K) and cellular damage due to oxidative stress (vitamin E), vitamin D is particularly relevant in scenarios where sun exposure is limited, such as in a large-scale ASRS, because the lack of sunlight directly affects the body's ability to produce vitamin D naturally, which made it a focal point for this research.
On the other hand, the purpose of the research was to narrow the focus to delve deeper into a specific area, and vitamin D was selected because there were already some foods proposed in the ALLFED article, which facilitated the development of the analysis without excessively broadening the scope because the time planned for the preparation of the article was relatively short. Due to the exploratory nature of the project, the aim was to propose viable solutions for a crucial micronutrient, leaving room for future research to complement and enrich this field of research.
I hope I have answered your question and I greatly appreciate your comments.