BACKGROUNDSodium-glucose cotransporter-2 inhibitors (SGLT2i) are widely used in managing type 2 diabetes (T2D). A significant number of these patients choose to observe religious fasting during Ramadan. Although existing guidelines recommend caution when administering SGLT2i during Ramadan due to potential adverse effects, there is limited data on their use in this patient population.AIMTo assess the safety and effectiveness of SGLT2i in patients with T2D who fast during Ramadan.METHODSRelevant studies involving adults with T2D who received an SGLT2i in the intervention arm and other glucose-lowering drugs in the control arm were systematically searched through electronic databases. The primary outcome was the occurrence of adverse events in the two groups; additional outcomes included changes in glycemic and anthropometric parameters during the peri-Ramadan period. RevMan Web was used to conduct meta-analysis using random-effects models. Outcomes were presented as mean differences (MDs) or risk ratios (RRs) with 95%CI.RESULTSTwelve studies involving 3625 subjects were included. The risks of postural dizziness (RR = 6.39, 95%CI: 1.58-25.80, P = 0.009, I2 = 44%), hypotension/postural hypotension (RR = 4.43, 95%CI: 1.35-14.55, P = 0.01, I2 = 31%), and sodium loss (MD = -1.00 mmol/L, 95%CI: -1.34 to -0.67, P < 0.00001, I2 = 0%) were higher in the SGLT2i group compared to the non-SGLT2i group. The SGLT-2i group achieved larger reductions in systolic (MD = -2.41 mmHg, 95%CI: -4.52 to -0.30, P = 0.02, I2 = 46%) and diastolic blood pressure (MD = -1.71 mmHg, 95%CI: -2.70 to -0.72, P = 0.0007, I2 = 20%), and experienced a lower risk of symptomatic hypoglycemia (RR = 0.53, 95%CI: 0.29-0.97, P = 0.04, I2 = 69%). The two groups exhibited comparable changes in glycated hemoglobin, body weight, and renal function. The risks of other specific adverse events, including dehydration, dizziness, volume depletion, symptomatic hyperglycemia, severe hypoglycemia, and genitourinary infections, were identical in the two groups.CONCLUSIONSGLT2i may be generally safe and effectively manage T2D during Ramadan; however, the results are less robust and should be interpreted with caution. Large multicenter randomized trials are necessary to confirm their safety, especially for at-risk groups, and to improve clinical decision-making.

To evaluate the outcomes of prolonged religious Jewish fasting in individuals with type 1 diabetes using automated insulin delivery (AID) systems. This cross-sectional, non-interventional study assessed the effects of a 25-hour Jewish fast in individuals using AID systems. Data was collected on the day of the fast, one week before, and one week after. The study included data from 109 fasting days involving 80 adolescents and young adults with type 1 diabetes. The mean age of participants was 17.4 ± 4.1 years; 47.5% were male, and the average duration of diabetes was 7.2 ± 4.3 years. A total of 67.6% of participants modified their AID system settings during the fasting period, with the most common modification being a change in the target glucose level. Overall, 71.5% completed the fast without complications. Fasts were primarily broken because of sensor-detected hypoglycemia. No cases of severe hypoglycemia or diabetic ketoacidosis were reported during or after the fasting period. During the fast, the mean blood glucose level was 135 ± 28.6 mg/dL, time in range (70-180 mg/dL) was 80.7%, and time spent in hypoglycemia (<70 mg/dL) was 2.6%. Prolonged fasting appears to be safe for adolescents and young adults with type 1 diabetes using AID systems. However, individualized adjustments to system settings are often necessary to maintain glycemic stability during fasting. To our knowledge, this is the first report of the effects of using an AID system during Jewish religious fasting.

Fasting, practiced in clinical, cultural, and faith-based contexts, has emerged as a non-pharmacological strategy capable of modulating multiple physiological systems. Contemporary evidence suggests that diverse fasting patterns (intermittent and time-restricted fasting, Ramadan fasting, alternate-day and periodic fasting, dry fasting, and fasting-mimicking diets) converge on shared metabolic-circadian-immune pathways and can be conceptualized within an integrated resilience framework. This narrative review synthesizes current experimental and human data on fasting as a multisystem health modulator, linking metabolic, cardiovascular, immune, gut-liver-microbiome, neurocognitive, endocrine, and psychospiritual effects to common regulatory axes, particularly the Metabolic-Circadian-Immune (MCI) and Energy-Information-Resilience (EIR) models. Across fasting modalities, activation of energy-sensing pathways (AMPK-SIRT1-mTOR), metabolic switching to lipolysis and ketogenesis, enhanced autophagy/mitophagy, and improved insulin sensitivity have been shown to support the management of obesity, type 2 diabetes, dyslipidemia, hypertension, and non-alcoholic fatty liver disease. Fasting also modulates immune and inflammatory tone, reshapes the gut microbiome, and may benefit autoimmune conditions such as rheumatoid arthritis and multiple sclerosis. Cardiovascular, endocrine, and neurocognitive domains show improvements in blood pressure, lipid profiles, neurotrophic signaling, mood, and cognitive resilience, while structured religious fasting (e.g., Ramadan) can additionally reinforce psychological discipline and spiritual well-being. At the same time, responses are heterogeneous, and prolonged or intensive regimens may pose risks in vulnerable populations. Fasting can be viewed as a low-cost, multidimensional "biopsychospiritual" health intervention acting through interconnected metabolic, circadian, immune, and neurobehavioral pathways. By integrating traditional and religious fasting practices with contemporary mechanistic and clinical data, this review highlights shared energy- and immune-regulatory axes and underscores the potential of fasting within integrative, preventive, and personalized care. Standardized protocols, long-term outcomes, and multimodal trials combining immunophenotyping, microbiome/metabolomic profiling, and neuroimaging remain priorities for future research.

Background/Objectives: Prolonged fasting-defined as voluntary abstinence from caloric intake for periods exceeding 24 h-is increasingly recognized not only as a metabolic intervention but also as a psycho-behavioral modulator. According to the 2024 international consensus, intermittent fasting encompasses diverse temporal patterns including time-restricted feeding, alternate-day fasting, and periodic fasting of multi-day duration. While metabolic benefits are well documented, the psychoneurobiological and psychiatric consequences remain incompletely characterized. This review critically appraises current evidence on the psychological and psychiatric effects of prolonged and intermittent fasting, including both secular and religious practices. Methods: A narrative synthesis was conducted on clinical trials, observational studies, and translational research published between January 2010 and June 2025 in PubMed, Scopus, and PsycINFO. Search terms included combinations of "prolonged fasting," "intermittent fasting," "psychological," "psychiatric," "religious fasting," "Ramadan," and "Orthodox Church." Eligible studies required explicit evaluation of mood, cognition, stress physiology, or psychiatric symptoms. Data were analyzed qualitatively, with particular attention to study quality, fasting regimen characteristics, and participant vulnerability. This is a non-registered narrative synthesis drawing on clinical trials, observational studies, and preclinical evidence published between January 2010 and June 2025. Results: Eighty-seven studies met inclusion criteria (39 human; 48 preclinical). In metabolically healthy adults, short-term time-restricted eating and supervised prolonged fasting were associated with modest reductions in depressive symptoms and perceived stress, with small improvements in executive functioning-typically observed in small samples and with limited follow-up. Religious fasting during Ramadan and the Orthodox Christian fasting periods demonstrated similar neuropsychological effects, including greater perceived spiritual meaning and affective modulation, though cultural context played a moderating role. Potential adverse mental-health impacts included mood destabilization, anxiety exacerbation, and rare psychotic or manic decompensations in vulnerable individuals. Randomized trials reported few adverse events and no signal for severe psychiatric harm, whereas observational studies more often noted symptom exacerbations in at-risk groups. Patients with eating disorder phenotypes exhibited increased cognitive preoccupation with food and a heightened risk of behavioral relapse. Methodological heterogeneity across studies-including variation in fasting protocols, psychological assessments, and follow-up duration-limited cross-study comparability. Conclusions: Evidence indicates a bidirectional relationship wherein fasting may foster psychological resilience in select populations while posing significant psychiatric risks in others. Inclusion of religious fasting traditions enriches understanding of culturally mediated outcomes. To enhance rigor and safety, future studies should incorporate clinician-rated outcomes (e.g., HDRS-17, CGI-S/CGI-I), standardized adverse-event tracking using validated psychiatric terminology, and prospective safety monitoring protocols, with ≥6-12-month follow-up.

The purpose of the article is to study the patterns of influence exerted by church rituals, religious fasts, and agricultural cycles on the reproductive behavior of Ukrainian peasants in the late 19th – early 20th century (based on the example of the parish of the Dmitry church in the village of Biloshytsi, Ovruch County, Volhynian Governorate). The research methodology is grounded in an interdisciplinary approach that combines methods of social history, particularly microhistorical analysis, historical demography, and historical-anthropological analysis. The primary source is parish metric books, which allow the tracing of birth dynamics and seasonality. The scientific novelty lies in the attempt to interpret the demographic behavior of the Ukrainian peasantry based on parish metric records from the end of the 19th to the beginning of the 20th century, using the case of a specific parish (the Dmitry church in Biloshytsi village, Volhynian Governorate). This provides new insights into how religious factors influenced reproductive decisions among the population. Conclusions. The analysis of seasonal fluctuations in births in the village of Biloshytsi, Ovruch County, Volhynian Governorate revealed that the reproductive behavior of Ukrainian peasants at the end of the 19th – beginning of the 20th century was largely determined by the agrarian calendar, whereas religious factors did not have a dominant influence on the sexual life of the peasantry. Although the Church remained an important social institution and retained authority in matters of marriage, its influence on the intimate life of peasants was limited. Thus, religious prohibitions on sexual relations during fasting periods did not determine the overall dynamics of birth rates. This suggests the existence of separate sociocultural dimensions – religious and corporeal – which often did not align. This mismatch led to various social consequences, including the formation of a double morality, where outward displays of religiosity and participation in rituals coexisted with private lives governed by other (often pragmatic) rules.

A Review to Assess the Safety and Health Outcomes of Religious Fasting in Ramadan in Patients Post Metabolic/Bariatric Surgery.

BackgroundVitamin D deficiency is highly prevalent in populations following intermittent or religious fasting, particularly Orthodox nuns with limited sun exposure and dietary restrictions. Vitamin D may modulate adipokines and inflammatory markers, but clinical evidence remains inconsistent.ObjectiveTo investigate the effects of vitamin D supplementation on interleukin-6 (IL-6) and leptin concentrations in Orthodox nuns compared with non-supplemented controls.MethodsIn this controlled, non-randomized trial, 33 Orthodox nuns received oral vitamin D3 supplementation (2,500 IU/day) for 16 weeks, while 42 age-matched women following Orthodox intermittent fasting served as controls. Anthropometric indices and serum concentrations of 25-hydroxyvitamin D [25(OH)D], IL-6, leptin, parathyroid hormone, insulin, and C-reactive protein were measured at baseline and follow-up.ResultsAt baseline, serum 25(OH)D concentrations were lower in the supplementation group compared with controls (23.4 ± 10.1 vs. 27.7 ± 11.2 ng/mL, p = 0.043). After 16 weeks, 25(OH)D increased significantly in the supplementation group (23.4 ± 10.1 vs. 33.9 ± 11.0 ng/mL, p < 0.001), with no change in controls (27.7 ± 11.2 vs. 28.5 ± 12.2 ng/mL, p = 0.941). Leptin showed a non-significant decrease in the supplementation group (24.4 ± 18.3 vs. 21.9 ± 13.5 ng/mL, p = 0.215), whereas in the controls, it remained unchanged (23.21 ± 14.67 vs. 24.05 ± 13.89 pg/mL, p = 0.365). IL-6 did not change significantly in either group. Exploratory multivariable regression did not reveal significant predictors of leptin changes.ConclusionsVitamin D supplementation effectively corrected deficiency but did not significantly affect leptin or IL-6 concentrations. These results highlight the need for larger and longer studies to further clarify the immunometabolic impact of vitamin D supplementation in women practicing intermittent fasting.

Association of Ethiopian Orthodox Tewahedo Christian fasting on appetite hormones and insulin sensitivity in type-II diabetes and healthy subjects in Ethiopia

Social and Cultural Barriers and Facilitators Affecting Mothers’ Dietary Practices in Eastern Ethiopia: A Qualitative Study

Background: Vitamin D supplementation may influence oxidative stress, but evidence in populations following specific dietary patterns is limited. Methods: In this non-randomized, two-group exploratory study, 50 Orthodox nuns received vitamin D supplementation (2000 IU/day orally) for 16 weeks, whereas 50 age-matched women following time-restricted eating (TRE) served as controls receiving no supplementation. Anthropometric parameters, serum 25-hydroxyvitamin D [25(OH)D], and oxidative stress markers—total antioxidant capacity (TAC), glutathione (GSH), and thiobarbituric acid reactive substances—were measured at baseline and post-intervention. Results: At baseline, both groups were comparable in anthropometric and oxidative stress markers, except for serum 25-hydroxyvitamin D [25(OH)D], which was lower in the intervention group. Following supplementation, serum 25(OH)D increased from 15.77 ± 5.21 to 31.24 ± 7.87 ng/mL (p = 0.031) in Orthodox nuns. No significant changes were observed for TAC (0.93 ± 0.11 to 0.97 ± 0.09, p = 0.081) and GSH (6.01 ± 1.55 to 5.81 ± 1.41, p = 0.069), whereas TBARS decreased significantly (7.32 ± 1.31 to 6.94 ± 1.21, p = 0.041). No significant changes were observed in controls under TRE. Changes (Δ) in all variables represented the post–pre difference over the 16-week period. Pearson correlations showed no significant associations between Δ25(OH)D and ΔTAC (r = −0.244, p = 0.346), ΔGSH (r = 0.110, p = 0.675), or ΔTBARS (r = −0.116, p = 0.657). In multivariable regression adjusted for age, weight, body fat percentage, and baseline 25(OH)D, Δ25(OH)D was not an independent predictor of oxidative stress marker changes; however, weight (β = 0.08, p = 0.011) and body fat percentage (β = −0.13, p = 0.014) were associated with reductions in TBARS. Conclusions: In conclusion, sixteen weeks of vitamin D supplementation in women adhering to Orthodox fasting produced no consistent improvements in oxidative stress markers. While a small reduction in TBARS was observed, this effect was modest and appeared indirect, being more closely associated with decreases in body weight and fat mass than with vitamin D status itself. Taken together, our findings indicate an overall neutral impact of vitamin D on redox balance, suggesting that any antioxidant benefit is likely secondary to metabolic or adiposity-related changes.

The practice of religious fasting among patients treated for breast cancer during radiotherapy

Vitamin D3 supplementation in women practicing orthodox religious and intermittent fasting: A controlled study with formulation-specific effects

Fish play a vital role in ensuring food and nutritional security by providing high-quality protein, essential fatty acids, vitamins, and minerals. Despite Bihar’s rich inland water resources, per capita fish consumption remains lower than the national average. This study aimed to assess fish consumption patterns, preferred species, and nutritional awareness among residents of Sitamarhi district, Bihar, India. A descriptive cross-sectional survey was conducted from July 2024 to March 2025 using a structured Google Forms questionnaire administered to 120 respondents, including students, professionals, and fish vendors. Data on socio-demographic profiles, dietary preferences, frequency of fish consumption, species choice, and awareness of nutritional benefits were collected. Additionally, field visits and market observations were conducted in major fish trading hubs such as Bazar Samiti, Gudri Bazar, Kargil Chowk, Bathnaha Bazar and Dumra. Quantitative data were analyzed using Microsoft Excel, and results were presented using descriptive statistics, tables, and figures. Among respondents, 78% were non-vegetarian, of whom 72% consume fish. Weekly consumption was most common (37.2%), followed by occasional (33.9%) and rare (28.9%) intake. Rohu (Labeo rohita, 20%), Bhakura (Catla catla,18%), Gaicha (Mastacembelus pancalus, 16 %) and Bighat (Hypophthalamichthyes molitrix, 12 %) were the most preferred species. While 85% of fish consumers recognized its role in brain health, fewer were aware of its cardiovascular and immune system benefits. Seasonal availability, religious fasting, and affordability significantly influenced consumption trends. Most consumers (72%) purchased fish from markets, with a smaller proportion sourcing from local ponds or farms. Fish is a culturally valued and widely consumed protein source in Sitamarhi, but comprehensive nutritional awareness remains limited. Enhancing public education, strengthening cold chain infrastructure, and promoting sustainable aquaculture could significantly improve fish consumption and rural livelihoods in the district.

Introduction: Effect of fasting on human cognition has been a topic of recent research. The results of those studies are contradictory at best. Moreover, fasting as a religious ritual for an entire holy month of Ramadan has many denominators that differs from other pattern of fasting. Data on cognitive functions of physicians during Ramadan is scarce. We had investigated the effect of Ramadan fasting on physicians who are actively engaged in treating patients. Materials and Methods: This was a cross-sectional study conducted on 53 doctors working in a teaching hospital. Basic and task specific data were collected 1 week before and during Ramadan. On each occasion, cognition of each participant was tested using Trail making Test (TMT) part A and B, Simple reaction time (SRT) and Stroop test. Independent and paired t-test and multiple regression analysis were used for statistical analysis of Data in SPSS with significance level set at 0.05 or lower. Result: Overall, Ramadan fasting had no significant impact on cognitive capabilities of the physicians. Female participants (67.9%) performed better in TMT A and B and increased age was related to poorer results in SRT, TMT A and B. Higher diastolic blood pressure was associated with higher TMT B score. Neither sleep nor the blood glucose had any significant impact on cognition during Ramadan. Conclusion: In our study we had found no impairment of cognitive functions of treating physicians from different age group and specialties due the religious fasting on the holy month of Ramadan. Medicine Today 2025, Vol.37 (2): 237-240

Il “dovere del digiuno”. Astinenza dal cibo e sicurezza alimentare Despite the universal declaration of the right to food, global hunger remains a persistent crisis. Paradoxically, many of the world’s major religions incorporate fasting as a central practice, seemingly at odds with the fundamental need for sustenance. This essay explores this apparent contradiction, focusing on major religious traditions to examine the nuanced relationship between the right to food and the duty of fast. It argues that religious fasting, far from undermining food security, can cultivate values such as self-restraint, communal responsibility, and empathy for the hungry, indirectly supporting efforts to ensure more equitable access to food resources. Religious rules on fasting, in fact, can be instruments for managing the challenges of food insecurity. This paper analyses different meanings of fasting in religious laws, summarizing the altruistic view that underpins them. Moreover, this matter could be a point of the “strategy of dialogue” that is currently being developed in the EU under the umbrella of the Article 17 of the Treaty on the Functioning of the European Union The ultimate goal is to demonstrate that religious duties can be considered valuable legal resources in achieving global food security. SOMMARIO: 1. Introduction. The right to food in international law: foundations and challenges - 2. The intersection of religious laws and food security: values, authority, and influence - 3. Duties and practices of fasting in different religious legal traditions - 4. Functions of fasting in a globalised scenario: how duties and rights support each other, a) The critical function of the fasting deontology, b) The solidaristic/altruistic function of the fasting deontology - 5. Conclusions.

Tithinirṇaya is a celebrated astronomical text of the Mādhva tradition, intended primarily to assist in computing the appropriate days for observing a religious fast. For this purpose, it prescribes a procedure to obtain the tithi at sunrise for an observer located at latitude (φ) near 12.780. This work supplies a translation of the text along with mathematical and geometric rationales for the astronomical algorithms presented therein, which are either inadequate or missing in prior publications. The work also investigates the disputed authorship of the text and briefly remarks upon its religious applications.

Aim: to identify sociocultural factors influencing the providing of dental care to foreign students. Material and methods. A survey was conducted among 160 foreign students, the average age was 23,0 years (18÷36), among them 72 were men (45,0 %) and 88 were women (55,0 %). An anonymous questionnaire was provided in paper form in English. The analysis of dependencies was carried out using the Pearson chi-square criterion. Results. the presence of restrictions on taking med-ications during religious fasting was revealed in 122 people (75,8 %), as well as the evaluation of the im-portance of gender when choosing a dentist showed that gender is important for 60 people (42,2 %). The change in the number of students who answered that they have restrictions on taking medications during re-ligious fasting from one year of education to other was statistically significant (p = 0,005). In pairwise compar-ison we obtained a significant decrease in the number of students who answered that they have restrictions on taking medications during lent, from the second to the third year of study. When assessing the importance of gender when choosing a dentist, we found that the number of answers “the doctor’s gender does not mat-ter” increases from the second to the fifth year. The increase in the number of answers is significant both in the overall assessment (total p &lt; 0,001) and in pairwise comparison of the 2nd year with each of the courses (for each pair p &lt; 0,001). Conclusion. Improving dental care through the de-velopment of patient-oriented approaches taking into account socio-cultural factors will help increase the commitment of foreign students to dental treatment, and therefore help maintain and improve oral health dur-ing their stay in the Russia.

BackgroundIt’s crucial for individuals with diabetes to practice effective self-management to reach their treatment goals and to prevent complications.AimThis study aimed to explore needs and challenges in diabetes self-management for patients with type 2 diabetes (T2D) and healthcare providers in Addis Ababa, Ethiopia, between February and April 2023.MethodsThis study employed a mixed method approach, with an exploratory qualitative study, including in-depth interviews with 22 patients with diabetes and key informant interviews with 25 healthcare providers. Additionally, we conducted a quantitative assessment of 26 primary health care facilities to understand facility-related factors that impact diabetes self-management practices. Thematic analysis was performed using a deductive coding approach following the socioecological model, with the help of Open Code software.FindingsThis study revealed that poor diabetes self-management practices are a major risk factor for blood glucose control among patients with type 2 diabetes. Patients struggled with misconceptions, low health literacy, dietary preferences, a lack of glucometers, financial constraints, age-related issues, and comorbidities. Healthcare system factors included insufficient trained staff, the absence of health insurance coverage, inadequate diabetes education, the scarcity of educational resources, and limited access to affordable diagnostic facilities. At the community level, a lack of social support, self-stigma, religious fasting practices, and restricted access to diverse food options were prominent obstacles. Patients expressed preferences for accessible educational materials such as pamphlets, mobile messages, and localized TV programs. Healthcare providers emphasized the necessity for culturally appropriate guidelines tailored to local contexts, emphasizing patient understanding and personalized care.ConclusionsThis study found that inadequate diabetes self-management practices are the risk behaviours for poor blood glucose control in patients with T2D and these issues are associated with challenges at the patient, organizational, and community levels. This study highlights the need for tailored diabetes self-management programs in Ethiopian primary healthcare, considering local contexts, diabetes health literacy, participant demographics, and evolving patient needs.

In this study, we examine whether religiosity affects people's levels of smoking. We use the month of Ramadan, a sacred month for Muslims, as an exogenous change for religiosity. In this month, there is less opportunity to smoke for fasters. First, we conducted a survey at different times: once before Ramadan, four times during Ramadan (one survey per week), and once after Ramadan. Secondly, we utilized monthly administrative cigarette sales data between 2009 and 2020. Individual level data from the survey shows that full fasters reduce their smoking by 53% drop during Ramadan compared to the pre-Ramadan sample. Cigarette sales drop as much as 14% in the month of Ramadan in Turkey overall. A regular Ramadan day lowers cigarette sales around 0.8%. Reduction in Ramadan is much higher in more religious provinces. This study demonstrates that limiting the opportunity to smoke can be an effective way to reduce smoking. Based on two complementary studies-a six-wave survey of 769 individuals and an analysis of provincial-level cigarette sales from 2009 to 2020-this research shows that Ramadan significantly reduces smoking intensity and cigarette sales. Full fasters decreased smoking by 53%, and national cigarette sales fell by 14%. The effect was more pronounced in more religious provinces. These findings suggest that even short-term restrictions on smoking opportunities can lead to substantial behavioral changes, despite the addictive nature of tobacco use. These findings offer valuable insights for public health policies aiming to reduce smoking through culturally sensitive and opportunity-limiting interventions.

Background: Vitamin D plays a key role in bone metabolism and immune regulation. Populations with restricted sun exposure or limited dietary intake are particularly vulnerable to vitamin D deficiency. Orthodox Christian nuns represent a unique group in this regard, due to traditional clothing, limited outdoor activity, and prolonged religious fasting. However, few studies have compared them with lay individuals following similar dietary practices. Objective: This study aimed to investigate predictors of serum 25-hydroxyvitamin D [25(OH)D] concentrations in two female populations: Orthodox Christian nuns and women from the general population practicing intermittent (religious or non-religious) fasting. We also aimed to develop predictive models of vitamin D status for each group based on lifestyle and biochemical parameters. Methods: A total of 85 women (40 Orthodox nuns and 45 laywomen), aged 30-50 years, were enrolled. Serum 25(OH)D, parathyroid hormone (PTH), calcium levels, and anthropometric indices, including body mass index (BMI), total body fat, and visceral fat, were measured. Dietary calcium and vitamin D intake, as well as sun exposure, were assessed using validated questionnaires. Separate stepwise multiple regression models were constructed for each group to identify independent predictors of 25(OH)D concentrations. An additional combined model, including all participants, was also explored. Results: PTH was the most significant predictor, negatively correlating with 25(OH)D concentrations in both groups (p = 0.038), highlighting its regulatory role in vitamin D metabolism. When analyzed separately, the model for Orthodox nuns showed stronger explanatory power (adjusted R2 = 0.718; p = 0.013) compared with the control group (adjusted R2 = 0.362; p = 0.038), with PTH emerging as a key predictor in both. Conclusions: Distinct predictors of vitamin D status were identified in each group, reflecting the complex interplay between lifestyle and physiological factors. These findings suggest that targeted interventions, such as addressing PTH regulation in fasting populations or enhancing sun exposure in the general population, may be more effective in preventing vitamin D deficiency depending on the context.