Myth-buster
Weekly 15,000 IU vitamin D for lactating mothers boosted infant blood levels by 14.7 nmol/L — yet the same trial found no reduction in rickets or improvement in growth or motor development.
While the study reinforces that vitamin D supplementation effectively raises blood levels (a pattern seen across three prior trials), the lack of any clinical benefit for rickets, growth, or motor skills in these infants cautions against assuming that correcting a biomarker automatically improves health outcomes in this population.
In a double-blind trial in rural Ethiopia, lactating mothers who took 15,000 IU of vitamin D3 each week had infants with significantly higher vitamin D levels at 12 months compared to placebo — a rise of about 14.7 nmol/L. However, the same study found no difference in suspected rickets cases, infant growth, or gross motor development, meaning the benefit was limited to a blood test improvement rather than any measurable health gain.
Where this fits in the evidence
Pillser has synthesized 3 studies on Vitamin D for Improved Vitamin D Levels — overall evidence strength: Moderate.
Across 3 studies, 3 reported beneficial moderate-sized effects of vitamin D supplementation on improving vitamin D levels. The most-studied dose ranges were high daily doses (5000-7943 IU) or weekly 15,000 IU, with effects observed at a median duration of 365 days.
The study
- Randomized Controlled Trial (RCT)
- 2025-11
- The American journal of clinical nutrition
This is a plain-language summary of a research finding, not medical advice. Pillser surfaces research signals to help you decide what's worth investigating — always consult a qualified professional before changing what you take.