Vitamin D supplementation reduces infection rate and promotes wound healing in patients with diabetic foot ulcers

Table 1 The study population's baseline characteristics

Baseline characteristics	VD group (n = 60)	Control group (n = 60)	P value
Mean age/(years)	65.4 ± 8.3	64.7 ± 7.9	-
Sex distribution	53.3% male, 46.7% female	55.0% male, 45.0% female	-
Duration of diabetes (years)	12.1 ± 5.6	11.8 ± 5.2	-
Ulcer size (cm²)	5.6 ± 2.1	5.4 ± 2.3	0.62
Ulcer severity	Moderate to severe	Moderate to severe	-
Baseline serum 25-(OH)D levels	16.5 ± 4.8 ng/mL	17.1 ± 5.0 ng/mL	0.47
HbA1c (%)	8.5 ± 1.2	8.6 ± 1.3	0.74
Other factors (BP, BMI)	Comparable across both groups	Comparable across both groups	-

Categorical variables are represented as percentages, while continuous variables are represented as mean ± SD. No significant differences were found between the vitamin D and control groups for any baseline characteristics (P > 0.05), ensuring comparability between groups. VD: Vitamin D; HbA1c: Glycated hemoglobulin A1c; BMI: Body mass index; BP: Blood pressure.

Table 2 Infection rates and severity in the vitamin D and control cohorts during 12-week intervention period

Infection outcome	VD group (n = 60)	Control group (n = 60)	P value	Absolute risk reduction
Infection incidence (%)	25% (15/60)	45% (27/60)	0.01	20%
Infection rate per 100 patient-days	3.2	5.8	0.01	—
Relative risk reduction	44%	—	—	—
95% confidence interval (infection incidence)	18.0% to 32.0%	36.0% to 54.0%	—	—
Severe infections requiring antibiotics (%)	10% (6/60)	25% (15/60)	0.03	15%
Hospitalization due to infection (%)	5% (3/60)	13% (8/60)	—	8%

The table includes absolute risk reduction values for key outcomes, showing a 20% absolute reduction in overall infection incidence and similar reductions in antibiotic use and hospitalization. VD: Vitamin D.

Table 3 The secondary outcomes: Wound healing, serum 25(OH)D levels, immune markers, and adverse events

Secondary outcome	VD group (n = 60)	Control group (n = 60)	P value
Wound healing
Baseline ulcer size (cm²)	5.6	5.4	-
Ulcer size at 6 weeks (cm²)	3.6 (35% reduction from baseline)	4.3 (20% reduction from baseline)	-
Ulcer size at 12 weeks (cm²)	2.2 (60% reduction from baseline)	3.5 (35% reduction from baseline)	< 0.01
Complete ulcer closure (%)	20%	10%	-
Serum 25(OH)D levels (ng/mL)
Baseline	16.5 ± 4.8	17.1 ± 5.0	0.47
Post-intervention (12 weeks)	35.2 ± 7.5	18.3 ± 5.2	< 0.001
Immune markers
Cathelicidin (change from baseline)	+30%	No significant change	< 0.01
Pro-inflammatory cytokines (IL-6, TNF-α)	-20%	No significant change	0.02
Adverse events
Hypercalcemia	0 cases	0 cases	-
Other side effects	None reported	None reported	-

Vitamin D (VD) supplementation correlated with notable enhancements in wound healing and serum 25(OH)D concentrations, along with an augmented immunological response, as shown by alterations in cathelicidin and pro-inflammatory cytokines. No adverse events were reported in either group, confirming the safety and tolerability of VD supplementation at 2000 IU/day. VD: Vitamin D; TNF-α: Tumor necrosis factor-α; IL: Interleukin.