Vitamin D3
Fat-soluble vitamin the skin makes from sunlight, and which regulates how the body absorbs calcium.
What the research shows
Shown repeatedly in humans, in reviews or meta-analyses.
Martineau's 2017 individual participant data meta-analysis found fewer acute respiratory infections, with the clearest difference for daily dosing and in people with low blood levels. Yao (2019) saw fewer fractures only when vitamin D was given together with calcium. Reid (2014) found almost no difference in bone mineral density.
Who it makes sense for: People with low vitamin D levels: older adults, people with darker skin, pregnant women and anyone who gets little sun in winter.
How we weigh evidenceClinical dosage
Scientific sources
The clinical dosages on this page are based on peer-reviewed research.
- Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.Martineau AR et al. (2017)
- Vitamin D and Calcium for the Prevention of Fracture: A Systematic Review and Meta-analysis.Yao P et al. (2019)
- Effects of vitamin D supplements on bone mineral density: a systematic review and meta-analysis.Reid IR et al. (2014)
We keep the dosages and values on this page as accurate as possible based on selected studies. New research may change these values. Nothing on this page is medical advice. If you have any doubts, always consult a doctor.