The goal of this randomized controlled clinical trial is to investigate the effects of vitamin D3 supplementation on cardiometabolic risk in Chinese adolescents with overweight/obesity and vitamin D deficiency. The main question it aims to answer whether vitamin D3 supplementation can improve cardiovascular metabolic health.
Participants in the intervention group will receive vitamin D3. The control group will receive vitamin D placebo.
Researchers will compare the change in cardiometabolic risk from baseline to post-intervention at 12 weeks between the intervention and control groups.
Students whose caregivers signed informed consents;
Students with serum 25(OH)D concentration of 12-20 ng/mL;
Students with overweight or obesity.
Students with any disease that affects vitamin D metabolism (e.g., functional/organic brain disease, severe infectious disease, chronic gastrointestinal disease, hepatic or renal insufficiency, etc.);
Students with known chronic disease (e.g., cardiovascular disease); use of vitamin D supplements in the past 3 months;
Students with allergies to vitamin D or soybean oil ingredients.
Parallel
Dietary Supplement: Vitamin D3
Drug2000 IU per day for 6 weeks (two capsules of 800 IU plus one capsule of 400 IU), followed by 800 IU (one capsule of 800 IU) per day for 6 weeks.
Dietary Supplement: Vitamin D3 placebo
DrugThree capsules for 6 weeks, followed by one capsule for 6 weeks.
Change in cardiometabolic risk scores
The cardiovascular metabolic risk scores was the sum of the sex-specific standardized z-score for 5 indicators: WC, MAP (MAP=1/3\*SBP+2/3\*DBP), HDL-C (HDL-C value multiplied by -1), TG, and fasting glucose. A higher cardiometabolic risk scores indicates a higher individual cardiometabolic risk. Change in cardiometabolic risk scores from pre to post-intervention were compared between randomized groups, which was the primary outcome of this study
BMI
Measurements were taken by trained researchers using a height and weight meter. The instrument was calibrated before the measurement and the subjects were asked to remove their shoes and wear light clothes during the measurement. We used weight in kilograms and height in metres to calculate BMI. The unit of BMI is kg/m\^2, BMI=Weight/(Height\*2) in kg/m\^2.
Waist circumference and Sum of skinfold thickness
Subcutaneous fat thickness was measured in the upper arm (at the midpoint of the line between the acromion point and the ulnar humerus), subscapularis (1 cm below the subscapularis) and abdomen (junction of the right midclavicular line and the umbilical level) using a skinfold thickness gauge after uniform training, with the results expressed in mm to one decimal place, and all of which required zeroing and pressure testing work of the skinfold thickness gauge before use. Waist circumference was measured using a corrected tape measure, circling horizontally along the midpoints of the lower edge of the ribs and the upper edge of the hip bone, and readings were recorded at the end of expiration to an accuracy of 0.1 cm.
Blood pressure
The researchers measured systolic and diastolic blood pressure using an Omron HEM-7124 digital sphygmomanometer. Measurements were taken with the subject in a sitting position and started after 10 minutes of sitting still, with 2 measurements taken at 5 minute intervals. The average of the two measurements will be taken.
Blood glucose and lipid
After each subject fasted overnight, the next day two professional nurses took their fasting blood samples by venipuncture, the blood samples were stored in an insulated box with ice packs, and all the samples were immediately transported to the laboratory to be tested by the professionals, and the indexes measured included fasting blood glucose, total cholesterol, triglycerides, HDL cholesterol and LDL cholesterol.
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