Coffee consumption and its association with vitamin D level, lifestyle factors, and mental health symptoms among adults in Saudi Arabia.

Coffee is widely consumed in Saudi Arabia, but its relationship with vitamin D status and related health indicators remains unclear. This cross-sectional study examined associations between coffee consumption, serum 25-hydroxyvitamin D [25(OH)D], lifestyle factors, and mental health symptoms in 387 adults aged 20-60 years recruited in Saudi Arabia (February-March 2024). Participants were classified as normal (≤3 cups/day) or high (>3 cups/day) coffee consumers. Anthropometric measures and serum 25(OH)D and parathyroid hormone were obtained from medical records, and diet, physical activity, sun exposure, and mental health symptoms were assessed by questionnaire. Associations were examined using group comparisons and multivariable regression models. Compared with normal coffee consumers, high coffee consumers had higher BMI (p = 0.043) and lower serum 25(OH)D (p = 0.05). In multivariable linear regression, higher caffeine intake was associated with lower serum 25(OH)D (β = -0.04 nmol/L per mg/day; 95 % CI -0.055 to -0.027; p < 0.001). In logistic regression, higher caffeine intake was associated with lower odds of vitamin D deficiency (<30 nmol/L) (OR = 0.98 per mg/day; 95 % CI 0.97-0.99; p < 0.001). High coffee consumers more frequently reported sleep disturbance/insomnia (49.1 % vs 34.2 %), sweating (20.8 % vs 9.6 %), and raised heart rate (27.7 % vs 17.2 %) (all p < 0.01), whereas headache, irritability, anxiety, and depression did not differ between groups. In this sample of Saudi adults, higher coffee intake was associated with lower 25(OH)D, higher BMI, and more arousal-related symptoms. These observational findings warrant confirmation in longitudinal or interventional studies to clarify temporality and inform public health strategies.