Reply to: “Is oral collagen the elixir of youth?”

Following letter provides answers and explanations for the correspoundance titled “Is oral collagen the elixir of youth.” They have admitted the strengths of our study and also have raised some questions about it, which we aim to provide answers and explanations.

and also have raised some questions about it, which we aim to provide answers and explanations.
To the Editor, We thank the authors for their comments on our manuscript entitled study assessing the tolerability and efficacy of an oral collagen supplement for the improvement of biophysical and ultrasonographic parameters of skin in Middle Eastern consumers. 1They have admitted the strengths of our study and also have raised some questions about it, which we aim to provide answers and explanations.
There were some comments about the study exclusion criteria.
It should be considered that since the study was conducted in Iran, where alcohol consumption is prohibited for religious and cultural reasons, alcohol use was not a relevant factor to assess or control.
The participants were residents of Iran who followed the prevalent Islamic customs of abstaining from alcohol.Thus, alcohol consumption was effectively excluded in this population.However, the authors make a fair critique that we should have explicitly stated this in the exclusion criteria section of the manuscript.About the diet change and possible hormone replacement therapy, it should be explained that the typical Iranian diet is not centered on high-fat and fast foods, but rather home-cooked meals and a Mediterranean-style diet with lots of vegetables, moderate fat, and spices.The subjects in our single group, before-and-after clinical study served as their own controls at baseline, meaning their regular diets were maintained throughout the 12-week study period.This removed diet as a significant confounding variable in the pre-post comparisons.Regarding hormonal therapy, there were no major changes in the lifestyle of the panelists over the course of the 12-week study.Participants were instructed to maintain their normal routines in terms of dietary intake, exercise habits, facial skin care regimens and use of any hormonal medications like birth control or hormone replacement therapy.
The authors stated that the test product contains hydrolyzed collagen from a marine source and it cannot be determined whether participants with allergies specifically to fish or soy were permitted to enroll in this study.We appreciate for bringing this oversight to our attention, however, no allergic reactions were observed during the actual study.Moreover, to confirm, subjects were recruited from our human volunteer bank who had no known history of fish or soy allergies based on medical records and self-reports.
The authors asked about skin-related pathologies such as psoriasis, eczema, or melasma and also the permission to use routine facial skin cleansing, moisturizing, and makeup by the participants.To clarify, we did not enroll subjects with diagnosed diseases.Only participants with healthy skin were recruited.Their regular facial skin care regimens were maintained throughout the study, including make-up, cleansers, and moisturizers.However, these were not applied on clinic assessment days to avoid interference with evaluations.Additionally, subjects refrained from using any anti-aging skin care preparations or procedures in the 4 weeks before and during the 12-week study period.
They also argued that while the sample size was small and only included people residing in Iran, it is difficult to generalize the study's findings to the Middle Eastern population as a whole.
As noted in the manuscript, the small sample size of participants is an acknowledged limitation, though we were still able to demonstrate statistically significant results.Although the sample was limited to Iran, we believe the results can be extended to other Middle Eastern populations given considerable shared factors like culture, diet, skin phototypes, environmental conditions like UV radiation levels, and genetics.These mentioned commonalities across Middle Eastern countries allow for reasonable extrapolation of the significant findings beyond just Iran.
The authors also claimed that the participants' questionnaire faces the possibility of potential recall bias and could tip responses toward possible exaggeration as well.
It should be considered that we asked about the present situation of the participants' skin in case of dryness and possible improvement in elasticity and appearance and it could not raise any recall bias.For preparing the questions, standard questionnaires of similar articles were applied for the feasibility of comparison. 2 Moreover, another assessment was performed including the participants' overall satisfaction with the treatment, using the visual analog scale, and the results in 3 visits (6.9 ± 1.86, 6.78 ± 2.17, and 6.56 ± 1.75 out of 10), confirmed the findings which were described in figure 2.
In conclusion, we also believe that the present study faced some limitations and confirm that a larger and more diverse sample size will help to promote the reliability of the data, however, according to the limited information on this subject, in the case of darker skin prototypes and Middle Eastern consumers, the current research could be considered a pilot study to suggest some clues for future.

DATA AVA I L A B I L I T Y S TAT E M E N T
Not applicable.

E TH I C S S TATEM ENT
The original study conducted in accordance with Declaration of Helsinki, and written informed consent was obtained from all the participants.However, the current letter is a reply to a correspondence, and no ethical issue would be applicable.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.© 2023 The Authors.Journal of Cosmetic Dermatology published by Wiley Periodicals LLC.C ORR ES P O ND ENC E Aniseh Samadi MD, PhD Saman Ahmad Nasrollahi PharmD, PhD Alireza Firooz MD Center for Research & Training in Skin Diseases & Leprosy, Tehran University of Medical Sciences, Tehran, Iran Correspondence Alireza Firooz, Center for Research & Training in Skin Diseases & Leprosy, Tehran University of Medical Sciences, # 415 Taleqani Ave, Tehran, Iran.Email: firozali@tums.ac.ir O RCI D Aniseh Samadi https://orcid.org/0000-0002-0134-429XSaman Ahmad Nasrollahi https://orcid.org/0000-0002-7384-6686 R E FE R E N C E S