Vitamin D and calcium status in HYDRIA, Greece: associations with dietary and supplemental sources

Serum vitamin D and calcium levels have been associated with health outcomes, while their deficiency, especially of vitamin D, is prevalent worldwide. This study aimed to estimate serum vitamin D and calcium levels in Greece, describe dietary intakes and supplement use, and identify characteristics associated with their status. The study included 685 HYDRIA participants aged ≥ 54 years. Associations of blood levels with demographic, lifestyle, and nutritional data were assessed via linear and logistic regression models. Mean serum vitamin D was 22.7 ng/ml (95% CI 21.6–23.8), significantly lower in women than men (21.1 vs. 24.6 ng/ml; p = 0.008). Vitamin D deficiency (< 20 ng/ml) affected 54.3% of women and 39.4% of men. Dietary intake was similar between sexes, though supplement use was higher among women (11.6% vs. 1.2%; p = 0.002). Vitamin D levels were significantly associated with supplement use (8.31 ng/ml; p < 0.001), high education (2.96; p = 0.016), sex (− 4.04 ng/ml in women; p = 0.001) and age, with levels rising at younger ages and plateauing or declining at older ages. For calcium, women had lower intake than men (1053.1 vs. 860.4 mg/day; p < 0.001), and were the only group using calcium supplements (12.1%). Only calcium adjusted for a 2000 kcal diet was significantly associated with calcium blood levels (p = 0.024). These findings highlight a high prevalence of vitamin D deficiency, particularly among women. Apart from sex, supplement use was the only significant predictor of higher vitamin D levels, suggesting diet alone may be insufficient. Calcium dietary intake was lower in women. These results emphasize the importance of targeted interventions, such as personalized guidance and awareness campaigns. Further research is needed to quantify the impact of vitamin D and calcium deficiency on human health.