Acne vulgaris is a prevalent chronic inflammatory skin disorder affecting the pilosebaceous units, particularly during adolescence. It is estimated to affect approximately 80–90% of teenagers worldwide, often leading to significant psychosocial distress and potential scarring (1). The pathogenesis of acne involves a multifactorial interplay of increased sebum production, abnormal keratinization, Cutibacterium acnes colonization, and inflammatory responses (2). Recently, attention has turned toward the role of micronutrients, particularly vitamin D, in modulating inflammatory skin conditions, including acne (3).

Vitamin D, a fat-soluble secosteroid synthesized in the skin through ultraviolet-B exposure and obtained through dietary sources, plays a crucial role in calcium metabolism, immune modulation, and skin barrier function (4,5). It exerts anti-inflammatory effects by regulating cytokine expression and T-cell differentiation, thereby influencing various dermatological conditions (6). Emerging studies have suggested a potential link between low serum 25-hydroxyvitamin D [25(OH)D] levels and increased severity of acne vulgaris, proposing that vitamin D may influence sebum production and keratinocyte proliferation (7,8).

Despite growing interest, the relationship between serum vitamin D levels and acne severity remains inconclusive, with conflicting evidence across populations and study designs. Some reports have indicated a higher prevalence of vitamin D deficiency among individuals with moderate-to-severe acne (9), while others found no significant association (10). Given the rising incidence of vitamin D insufficiency in adolescents due to lifestyle and dietary factors, it is imperative to explore its role in acne pathogenesis.

This study aims to evaluate the correlation between serum vitamin D levels and the clinical severity of acne vulgaris in adolescents, potentially paving the way for new preventive or adjunctive treatment strategies.

This cross-sectional observational study was conducted over a period of six months at the dermatology outpatient department of a tertiary care hospital. Ethical clearance was obtained from the institutional ethics committee prior to the commencement of the study, and written informed consent was collected from all participants and/or their guardians.

Study Population:

A total of 120 adolescents aged between 13 and 19 years, clinically diagnosed with acne vulgaris, were enrolled using purposive sampling. Exclusion criteria included individuals with other dermatological or systemic diseases, those on vitamin D supplementation in the past three months, and patients using oral retinoids or systemic antibiotics within four weeks of enrollment.

Acne Severity Assessment:

The severity of acne was evaluated using the Global Acne Grading System (GAGS), which considers lesion types and anatomical locations to assign a cumulative score. Based on GAGS, participants were categorized into three groups: mild (GAGS score ≤18), moderate (19–30), and severe (≥31).

Biochemical Analysis:

Venous blood samples (5 mL) were collected under aseptic conditions and centrifuged to separate serum. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured using a standardized chemiluminescent immunoassay method. Vitamin D status was categorized as sufficient (≥30 ng/mL), insufficient (20–29 ng/mL), or deficient (<20 ng/mL), in accordance with the Endocrine Society guidelines.

Statistical Analysis:

Data were entered into Microsoft Excel and analyzed using SPSS version 26.0. Continuous variables were expressed as mean ± standard deviation (SD), while categorical variables were summarized as frequencies and percentages. One-way ANOVA was used to compare serum vitamin D levels across acne severity groups. Pearson’s correlation coefficient was applied to assess the strength and direction of the relationship between GAGS scores and vitamin D levels. A p-value <0.05 was considered statistically significant.

A total of 120 adolescents with acne vulgaris were included in the study, comprising 58 males (48.3%) and 62 females (51.7%), with a mean age of 16.4 ± 1.9 years. Based on the Global Acne Grading System (GAGS), 40 participants (33.3%) had mild acne, 40 (33.3%) had moderate acne, and 40 (33.3%) had severe acne.

Serum Vitamin D Levels and Acne Severity

The mean serum 25(OH)D levels decreased progressively with increasing acne severity. Participants with mild acne had a mean vitamin D level of 28.7 ± 5.4 ng/mL, those with moderate acne had 21.3 ± 4.9 ng/mL, and those with severe acne had 14.6 ± 3.7 ng/mL. This difference was statistically significant (p < 0.001), as shown in Table 1.

Table 1: Mean Serum Vitamin D Levels According to Acne Severity

A significant negative correlation was identified between serum vitamin D levels and GAGS score (r = -0.72, p < 0.001), suggesting that lower vitamin D levels are associated with increased acne severity.

Distribution of Vitamin D Status Across Groups
Among participants with severe acne, 82.5% were found to be vitamin D deficient (<20 ng/mL), compared to 60% in the moderate group and 25% in the mild group. This distribution is summarized in Table 2.

Table 2: Distribution of Vitamin D Status by Acne Severity

The findings indicate a clear trend of lower vitamin D status among those with more severe forms of acne (Table 2).

The present study demonstrates a significant inverse correlation between serum 25-hydroxyvitamin D levels and the severity of acne vulgaris in adolescents. Participants with more severe acne exhibited notably lower serum vitamin D concentrations compared to those with milder forms of the condition. These findings support the growing body of evidence that vitamin D, beyond its well-established roles in calcium homeostasis and bone health, also modulates skin inflammation and immune responses (1,2).

Vitamin D influences the innate immune system by regulating the expression of antimicrobial peptides such as cathelicidin, which helps maintain skin barrier integrity and protect against microbial colonization, including Cutibacterium acnes (3,4). Furthermore, vitamin D suppresses pro-inflammatory cytokines, such as interleukin-6 and tumor necrosis factor-alpha, which are implicated in acne pathogenesis (5,6). This anti-inflammatory mechanism may explain the reduced severity of acne observed in individuals with sufficient vitamin D levels.

Several earlier studies have reported similar associations. Yildizgören and Togral (7) found significantly lower vitamin D levels in patients with moderate-to-severe acne compared to healthy controls. Likewise, Lim et al. (8) demonstrated that vitamin D inhibits the proliferation of sebocytes and reduces lipid production, further suggesting a mechanistic role in acne development. In a case-control study, Abdel Meguid et al. (9) observed that vitamin D supplementation improved acne lesion counts in deficient patients. These findings are consistent with the results of our study, where the majority of severe acne patients were vitamin D deficient.

Conversely, not all studies have found such associations. A study by Al-Shobaili (10) reported no significant difference in vitamin D levels between acne patients and controls, indicating that other environmental, hormonal, or genetic factors might also contribute to acne severity. Furthermore, methodological variations in acne grading systems, season of sample collection, and geographic sun exposure may account for discrepancies across studies (11,12).

The high prevalence of vitamin D deficiency observed in our study could also reflect broader lifestyle trends in adolescents, including reduced outdoor activity, sunscreen use, and dietary inadequacies (13). These lifestyle factors may amplify the inflammatory pathways associated with acne, especially in genetically predisposed individuals (14,15).

While our findings suggest a potential role of vitamin D in acne management, it remains unclear whether supplementation alone can serve as a primary therapeutic strategy. Future randomized controlled trials are warranted to evaluate the efficacy and safety of vitamin D supplementation in improving clinical outcomes in acne patients.

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