Researchers in India and Qatar observed that while a 400IU daily dosage was effective at eliminating deficiency, higher doses of 600-800IU were more consistently associated with attaining sufficiency, with 65.4% of participants receiving 800 IU\/day normalizing their levels by week 12.<\/p>\n
\u201cIn this context, serum 25(OH)D serves as a robust biochemical marker of vitamin D status, reflecting the cumulative effects of dietary intake and endogenous synthesis,\u201d they wrote in Nutrients.<\/p>\n
\u201cEmerging perspectives in precision nutrition further emphasize the role of such biomarkers in guiding individualized nutritional strategies, where biochemical responses may provide a more accurate basis for intervention than intake estimates alone.\u201d<\/p>\n
While high-dose regimens have been shown to achieve rapid normalization of vitamin D levels, the researchers noted their findings indicate that a gradual, sustained improvement in vitamin D status can be achieved with nutritionally relevant daily doses. <\/p>\n
Study details<\/p>\n
The double-blind, randomized controlled trial involved 108 non-pregnant, non-lactating Indian women aged 18\u201335 years with vitamin D insufficiency\/deficiency defined as serum 25-hydroxyvitamin D concentrations <20 ng\/mL.<\/p>\n
The participants were randomly assigned to one of four groups, each receiving a vitamin D3 daily dose of 0, 400, 600 or 800 IU, delivered as a fortified chocolate wafer for 12 weeks. The researchers collected data, including anthropometrics, blood samples, sun exposure, and dietary intake, at baseline, at weeks four and eight and at the end of the study. The supplemented wafer was the participants\u2019 primary source of vitamin D during the trial, as the intake of fortified dietary foods was negligible. <\/p>\n
The results showed that serum 25(OH)D concentrations increased significantly over time in all the supplemented groups, with a dose-dependent response.<\/p>\n
\u201cBy week 12, 65.4% of participants in the 800 IU group achieved vitamin D sufficiency (\u226520 ng\/mL), compared with 37.0% and 26.9% in the 600 IU and 400 IU groups, respectively and only 7.4% in the placebo group,\u201d the researchers wrote.<\/p>\n
They noted that \u201ceven the 400 IU dose (corresponding to Indian EAR) led to substantial improvements by week 4, with 23.1% of participants achieving vitamin D sufficiency\u201d.<\/p>\n
Although parathyroid hormone levels decreased over time, the researchers didn\u2019t observe significant differences in markers for bone turnover. They noted that this is consistent with previous research suggesting that vitamin D supplementation at nutritionally relevant doses, without concurrent calcium intake, has inconsistent and generally modest effects on bone turnover markers. <\/p>\n
The study limitations included a restricted population and the exclusion of physical activity, sun exposure, and dietary intake in the primary analytical models. The researchers noted that a longer future study period may more fully capture structural bone changes and longer-term skeletal adaptations.<\/p>\n