A comparative study to assess the effect of a vitamin d supplemented diet versus vitamin d supplementation on hba1cand lipid profile among patients with type 2 diabetes mellitus

Abstract

Abstract: Background: Type 2 diabetes mellitus (T2DM) is commonly accompanied by dyslipidaemia and a high burden of cardiovascular risk. Vitamin D has biological roles beyond bone metabolism, and observational research has linked lower circulating 25-hydroxyvitamin D [25(OH)D] concentrations with insulin resistance and adverse metabolic profiles. However, trials of vitamin D supplementation have produced inconsistent effects on glycated haemoglobin (HbA1c) and lipid fractions. It is therefore important to distinguish a food-based strategy from oral supplementation and to avoid presenting vitamin D as a replacement for established diabetes care. Aim: To compare changes in HbA1c and lipid profile among adults with T2DM receiving a structured vitamin D-rich or vitamin D-fortified dietary intervention and those receiving cliniciandirected oral vitamin D supplementation, in addition to usual diabetes care, at DH, Mohali. Methods: The proposed study is a prospective, two-group comparative intervention study with baseline and 12-week assessments. A target of 100 participants (approximately 50 per group) is proposed as a planning estimate. Participants will undergo clinical assessment, medication review, dietary assessment, HbA1c and fasting lipid testing, and measurement of serum 25(OH)D where feasible. Group allocation procedures, dose decisions, and eligibility for a diet-only strategy must be approved before recruitment. Clinically indicated vitamin D treatment will not be withheld. Primary outcome: Between-group difference in change in HbA1c from baseline to week 12. Secondary outcomes: changes in total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, serum 25(OH)D, body weight, dietary adherence, and safety events. Analysis will use an intentionto-treat principle where random allocation is approved and performed, with baseline-adjusted comparisons and confidence intervals. Expected contribution: The study is intended to generate locally relevant comparative evidence about practical vitamin D strategies in routine T2DM care. No numerical effect is predicted as an observed finding. Vitamin D supplementation will be interpreted as an adjunct for appropriate clinical indications, not as a substitute for glucose-lowering medicines, lipid-lowering therapy, medical nutrition therapy, physical activity, or follow-up. Protocol transparency: The final report should follow the applicable current trial-reporting guidance, provide the ethics approval and registration details, and report all prespecified outcomes regardless of statistical significance (Chan et al., 2025; Hopewell et al., 2025).