Evaluation the effect of combination use of synbiotics and vitamin D compared to their separate use on sexual function and sexual self-expression in lactating women: A randomized double blind clinical trial

Determination the effect of combination use of synbiotics and vitamin D compared to their separate use on sexual function and sexual self-expression in lactating women

112 eligible individuals are randomly assigned to three groups A (Vitamin D), B (Synbiotic), and C (combination of Vitamin D and Synbiotic) using block randomization. The randomized list of blocks of varying sizes (3, 6, and 9) is generated through a reliable website, and participants are allocated accordingly to ensure balanced numbers in each group and to reduce the predictability of group assignment.

This study will be conducted in Yasuj health centers after obtaining the necessary approvals and registration in the relevant systems. The intervention duration is 8 weeks. The study is double-blind, with the packaging and coding of supplements carried out by an independent person, ensuring that both participants and researchers are unaware of the type of intervention received.

Participants are lactating women aged 18 to 40, 1 to 4 months postpartum, and have sex at least once a month. They should not have a history of chronic diseases or have taken hormonal medications, antidepressants, or similar supplements in recent months. Also, women who are allergic to supplements or taking medications that affect sexual function will not be included in the study.

Group A: Received one vitamin D 1000 and one placebo supplement of synbiotic daily Group B: Received one synbiotic and one placebo supplement of Vitamin D 1000 daily Group C: Received vitamin D and synbiotic simultaneously daily

- Sexual function of breastfeeding women, assessed using the Female Sexual Function Index questionnaire - Level of sexual self-disclosure, assessed using the Halbert Sexual Self-Disclosure questionnaire

Individuals who meet the eligibility criteria for participation in the study will be assigned to the intervention groups. A block randomization method will be used to assign individuals to the study groups. The advantages of blocked randomization are that the balance of the number of patients in each group is guaranteed. The groups are defined as codes A, B, C. Group (A) receiving vitamin D 2. Group (B) receiving synbiotics 3. Group (C) receiving simultaneous consumption of vitamin D and synbiotics Before assigning individuals to one of the groups, a list of letters (A, B, C) in the form of blocks is formed. This random assignment list will be formed by the reliable website https://www.sealedenvelope.com. Each of the referring and eligible individuals will be assigned to one of the groups according to the created list. To prevent the predictable risk of assigning individuals to different groups, blocks of different sizes (3, 6, and 9) will be created. Triple blocks like ACB – Six-blocks like ABBCAD – Nine-blocks like DBCADACBA

This study will be double-blinded, meaning that neither the participants nor the researcher will know which intervention each person is receiving. The purpose of this method is to control bias. Double-blinding means that neither the participants nor the principal investigators and data collectors will be aware of the assigned group (synbiotic and vitamin D group simultaneously, separate group + placebo). To ensure complete and effective blinding, the following measures will be taken: * Supplement/placebo packaging and coding: - Synbiotic, vitamin D, and placebo supplements will be prepared and packaged by an independent individual outside the research team. To maintain the blinding structure in the study, the placebos used in this study will be prepared and formulated by the Drug Manufacturing Center of the Faculty of Pharmacy, Yasuj University of Medical Sciences. These placebos are made in the form of capsules without active ingredient but of the same shape, color and weight as the original supplements so that there is no possibility of differentiation by the participant or the researcher. In groups where only one of the supplements (vitamin D or synbiotic) is received, the second supplement will be replaced with placebo; so that all participants in all three groups will receive two capsules daily (one real supplement and one placebo or two real supplements). In this way, the double-blind structure and balance in the way of consumption are maintained. - All packages (both supplement and placebo) will have the same shape, color, taste, smell and appearance so that they are not physically distinguishable. - Each package will be labeled with a unique numeric or alphanumeric code, the meaning of which (which group it belongs to) is known only by the independent coder. - The coding list will remain confidential until the completion of data collection and initial statistical analysis and will only be opened in case of emergency (e.g. serious complications in the participant) or after the end of the study. * Distribution and monitoring: - Distribution of supplements/placebo to participants will be carried out by a person who is not part of the main research team and is unaware of the group allocation. - Follow-up procedures will be carried out to ensure correct and regular intake of supplements/placebo (e.g. counting remaining pills at subsequent visits), without providing information about the type of supplement to the participant or the data collector. * Data collection and analysis: - Data collectors who interact with participants will have no knowledge of the group allocation of participants. - The statistical analyst will also receive data based on blinded codes and will be unaware of the nature of groups A, B, and C until the end of the initial analysis.