Determinants of Treatment Response and Bone Health Outcomes with Calcium and Vitamin D Supplementation: Influence of Comorbidities, Lifestyle, Absorption and Nutrient Synergy

Background: Calcium and vitamin D are essential for skeletal health, yet treatment responses vary due to comorbidities, lifestyle factors, absorption issues, and nutrient interactions. Real-world data on how Indian physicians evaluate these determinants remain limited. This study examined physician-reported predictors of response, misconceptions, and practical factors influencing clinical outcomes with calcium and vitamin D supplementation. Methods: A cross-sectional, questionnaire-based study was conducted among 128 physicians across India using a structured 38-item form, of which 13 items relevant to treatment determinants were analysed. Physicians provided anonymised, experience-based responses based on their last 10 patients treated with calcium and vitamin D for osteoporosis or metabolic bone disorders. Key parameters included nutrient synergy, lifestyle advice, comorbidity-related variations, changes in muscle strength and BMD, dosing approaches, absorption barriers, common misconceptions, and methods for assessing long-term effectiveness. Data were summarised using descriptive statistics. Results: A total of 128 physicians participated in the survey. Vitamin K₂ was most frequently identified as the preferred adjunct to calcium and vitamin D (32.03%), while dietary modification was the most common lifestyle recommendation (42.97%). Comorbidities-particularly chronic kidney disease (37.50%), were perceived as key determinants of therapeutic response. Physicians reported moderate improvements in muscle strength (46.09%) and bone mineral density (39.06%). High fibre intake (42.97%) and proton pump inhibitor use (21.09%) were cited as major factors impairing absorption. Misconceptions included the belief that supplementation is only needed in the elderly (32.81%). Fracture reduction (40.63%) and composite assessments were the most used indicators of long-term effectiveness. Conclusion: The study highlights that comorbidities, nutrient interactions, lifestyle practices, and absorption factors significantly influence response to calcium and vitamin D supplementation, underscoring the need for individualised strategies and further research to optimise bone health.