Effect of Vitamin D Supplementation on Cardiometabolic Risks and Health-Related Quality of Life among Urban Premenopausal Women in a Tropical Country – A Randomized Controlled Trial

Randomized controlled trial in urban premenopausal women with vitamin D deficiency working at a public university in Kuala Lumpur, Malaysia. In the vitamin D arm, 93 participants were randomized and 93 were analyzed by intention to treat.

Oral cholecalciferol 50,000 IU powder diluted in warm water, given once weekly for 8 weeks and then once monthly for 10 months, for a total treatment duration of 12 months, versus placebo.

Vitamin D supplementation safely corrected vitamin D deficiency and lowered parathyroid hormone, but it did not meaningfully improve cardiometabolic risk factors. At 12 months, 25(OH)D rose to 85.74 nmol/l versus 36.09 nmol/l with placebo, with a mean difference of 49.54 (43.94 to 55.14), and PTH was 4.19 pmol/l versus 5.22 pmol/l, with a mean difference of -1.02 (-1.67 to 20.38). There were no meaningful differences in BMI, blood pressure, glucose, insulin, HOMA-IR, triglycerides, or HDL-C. The regimen also improved some health-related quality-of-life domains, especially vitality and mental health, and no vitamin D intoxication or adverse reaction was reported.

The trial was limited to a single urban population of mostly Malay, generally healthy premenopausal women, which restricts generalizability. The cardiometabolic outcomes were largely null despite a 12-month intervention, and the sample size was modest for detecting smaller clinical effects. Results may not extend to higher-risk groups, other ethnicities, or different dosing regimens.