Periodontal diseases are among the most prevalent oral conditions worldwide (1). In Colombia, the Fourth National Oral Health Survey (ENSAB IV) revealed that 61.8% of the population presented with periodontitis of varying severity, although with a higher frequency of moderate periodontitis (43.46%), followed by advanced periodontitis (10.62%). Only 38.2% of the population was found to be free of periodontitis, demonstrating that it is a highly prevalent oral pathology (2).

Periodontitis is a chronic infectious and inflammatory disease that is multifactorial and complex, affecting the supporting and protective tissues of the teeth. In general terms, it results from an imbalance in the immunological interaction between the host and the subgingival biofilm (3,4). The disruption in the uptake of vitamin D sources, due to various endogenous and/or exogenous factors, diminishes its levels, which may represent an indicator at the time of the diagnosis of these types of periodontitis (5), particularly considering that the critical physiological action of this vitamin is to increase intestinal calcium reabsorption, facilitate its renal absorption and promote bone mineralization. Therefore, vitamin D deficiency may be a risk factor for the development of gingivitis and periodontitis, highlighting the importance of this vitamin for bone and periodontal health (6).

The main clinical interest in vitamin D lies in the discovery of its receptors and the expression of the enzyme 1α-hydroxylase in various tissues. This has led to the identification of a wide range of effects of vitamin D in different tissues and physiological processes, such as antitumor activity, DNA repair, apoptosis control, oxidative stress, immunomodulation, cell adhesion, metabolism and another functions. Although research to date remains inconclusive, an association between low levels of vitamin D and various infectious, autoimmune, chronic and oral diseases has been suggested, linking it to periodontal health, given that insufficient vitamin D levels have been identified in patients with clinical attachment loss in the periodontium (6).

Vitamin D is acquired through dietary intake and cutaneous synthesis triggered by exposure to sunlight. Specifically, solar radiation induces the photolytic conversion of 7-dehydrocholesterol into previtamin D3 (precholecalciferol), which is then rapidly transformed into vitamin D3 (cholecalciferol). Notably, excessive sun exposure does not result in vitamin D toxicity (7,8).

Furthermore, the amount of melanin present in the skin affects the amount of vitamin D that can be produced. Individuals with greater amounts of melanin in the skin (those with darker skin types) have greater protection against the sun; however, they require a greater amount of sun exposure to synthesize vitamin D, rendering them more likely to experience vitamin D deficiency. Therefore, it is necessary to conduct examinations to assess their vitamin D levels and, if required, initiate treatment to improve vitamin D acquisition (9,10).

Several clinical trials have investigated the association between periodontal disease and vitamin D levels. These studies have included diverse patient populations receiving vitamin D supplementation, either alone or in combination with calcium or other medications. The findings suggest that vitamin D supplementation may reduce the risk of tooth loss (11), exert a dose-dependent anti-inflammatory effect on gingivitis (12) and inhibit pro-inflammatory cytokines, such as IL-1, IL-6, TNF-α and IL-10-in individuals with periodontitis (13).

Likewise, cross-sectional studies have demonstrated an association between low concentrations of vitamin D and periodontal disease (14,15); however, no significant association has been found between vitamin D deficiency and age (16). The association between vitamin D and skin phototype has also been evaluated, with findings indicating that in the majority of subjects with dark to very dark skin phototypes, there is a high prevalence of vitamin D deficiency, despite high sun exposure during the summer months (17). This suggests that the dark skin phototype is an endogenous factor that, even in a state o general health, may produce levels below the normal range of vitamin D and a possible tendency for the development of periodontitis.

Therefore, it is crucial to elucidate the association between periodontal disease and the consequences of vitamin D deficiency, particularly in patients with dark skin phototypes, due to their potential susceptibility to developing periodontal disease. Currently, to the best of our knowledge, there are no studies available on the association between vitamin D levels and periodontitis in patients with dark skin phototypes. Thus, the aim of the present study was to evaluate vitamin D levels in patients with dark skin phototypes who have been diagnosed with periodontitis.

A total of 79 patients who met all the inclusion criteria were enrolled. Of these, 72 (91.1%) were male and 7 (8.9%) were female. The average age of the patients was 33.4 years (SD ± 14.6), ranging from 18 to 75 years. As regards oral health, 8 patients (10.1%) had a healthy periodontium, 33 (41.8%) were diagnosed with gingivitis, 35 (44.3%) with stage I-II periodontitis and 3 (3.8%) with stage III-IV periodontitis. Some participants reported having risk factors related to their systemic condition, such as smoking, stress or allergies (Table I).

When assessing various sources of vitamin D uptake, such as sun exposure and the consumption of dairy products, cereals, natural juices and animal-derived protein, no statistically significant associations with periodontal diagnosis were observed; the association for dairy consumption exhibited a borderline trend (P=0.054; Table II).

The serum levels of vitamin D ranged between 2.0 and 43.3 ng/ml, with a mean of 22.6±7.1 ng/ml. Furthermore, all participants were categorized based on their serum vitamin D levels into sufficient, insufficient, or deficient levels. The majority of the patients were classified as having insufficient levels of vitamin D (Table IIIA). Across the periodontal diagnostic categories, serum 25(OH)D levels differed significantly overall (ANOVA P=0.005; Kruskal-Wallis test, P=0.00051) (Table IIIB). Post-hoc tests [applied only to 25(OH)D] indicated lower levels in those with stage III-IV periodontitis vs. healthy subjects (Tukey's test, P=0.041; Dunn-Bonferroni test, P=0.014), vs. those with stage I-II periodontitis (Dunn-Bonferroni test, P=0.034); a difference was also observed between those with gingivitis and stage I-II periodontitis (Dunn-Bonferroni test, P=0.026) (Table IIIC).

Additionally, when applying the Fitzpatrick criteria to determine skin phototype, 8 participants (10.1%) were classified as phototype III, 54 (68.4%) as phototype IV and 17 (21.5%) as phototype V. When these were associated with the patient groups, phototype IV was found to be the most prevalent among those with gingivitis and stage I-II periodontitis. Pairwise exact comparisons of phototype distributions across the diagnostic categories revealed differences for stage III vs. IV periodontitis (P=0.017), stage III vs. V periodontitis (P=0.018), and stage IV vs. V periodontitis (P<0.0001) (Table IVA).

Similarly, phototypes III, IV and V were compared against the vitamin D categories, no significant pairwise differences were detected (stage III vs. IV periodontitis, P=0.999; stage III vs. V periodontitis, P=0.999; stage IV vs. V periodontitis, P=0.673). Notably, both individuals with deficient vitamin D were phototype IV, and the majority of participants with phototypes IV and V were classified as insufficient (Table IVB).

The present study involved 79 patients, with a notable predominance of male participants (91.1%), which may reflect a gender disparity in the pursuit of dental care or a higher prevalence of periodontal conditions among males. This observation aligns with existing evidence identifying male sex as a non-primary risk factor for the development of chronic periodontitis (10). Moreover, the sex distribution within the Colombian armed forces, where males outnumber females at a ratio of ~60:1-may also explain this imbalance (20).

The oral health status varied considerably within the study sample, with a marked number of participants diagnosed with gingivitis or periodontitis at various stages, indicating a high burden of periodontal disease in this clinical setting. This pattern is consistent with reports of a higher periodontal disease burden among individuals with darker skin phototypes and in populations of African origin (21), although causal inferences cannot be drawn from our cross-sectional design. Consistent with the pairwise analyses, phototype distributions differed across periodontal diagnosis categories (Table IIIB). These observations underscore the importance of tailored periodontal care and preventive strategies.

The presence of systemic risk factors, such as smoking, stress and allergies further illustrates the multifactorial nature of periodontal disease and highlights the importance of a holistic, patient-centered approach to oral health and management.

As regards sources of vitamin D uptake, no statistically significant associations with periodontal diagnosis were observed; dairy intake exhibited only a borderline trend (P=0.054; Table II). Diet remains a plausible contributor to the vitamin D status and promoting vitamin D-rich or fortified foods may be considered (22), particularly given the predominance of insufficiency in our sample. Previous research has reported inverse associations between vitamin D and periodontal disease (23); however, the cross-sectional design of the present study and the absence of a direct analysis of dietary intake vs. vitamin D preclude causal inferences. The widespread insufficiency also raises concerns about bone integrity and immune function, both relevant to periodontal health, and supports the need for longitudinal and interventional studies to clarify the impact of improving vitamin D status on periodontal outcomes (21).

Concerning skin phototype and vitamin D categories, no statistically significant pairwise differences were detected (Fisher's test 2x3: stage III vs. IV periodontitis, P=0.999; stage III vs. V periodontitis, P=0.999; stage IV vs. V periodontitis, P=0.673; Table IVB). While both participants with deficient vitamin D levels were phototype IV, this subgroup was very small (n=2), and the pattern should be interpreted with caution. Given the influence of skin pigmentation on cutaneous vitamin D synthesis, phototype remains a relevant clinical consideration when evaluating vitamin D status and its potential implications for oral health (22).

However, certain limitations of the present study should be acknowledged. The relatively small sample size and the potential for selection bias may restrict the generalizability of the findings. Moreover, the lack of a large control group limits the ability to draw definitive conclusions regarding the association between vitamin D levels and periodontal disease within this population. Future research is thus required to prioritize longitudinal analyses for a more accurate investigation of the association between vitamin D status, oral health outcomes and systemic risk factors over time. Additionally, implementing targeted interventions to improve vitamin D levels and evaluating their effects on periodontal health could provide critical evidence to guide clinical practice and public health strategies.

In conclusion, the majority of the participants in the present study exhibited insufficient vitamin D levels, and lower levels were observed in those with advanced periodontitis. While phototype distributions varied across periodontal diagnosis categories, the phototype was not associated with vitamin D categories. No statistically significant associations were identified between sources of vitamin D intake and periodontal diagnosis (dairy intake exhibited only a borderline trend). These findings support considering vitamin D status within periodontal care for patients with darker phototypes and motivate longitudinal studies, ideally with validated dietary assessment and multivariable adjustment, to delineate causal pathways and evaluate targeted interventions.