Benefits of Vitamin D3

Evidence-Based Benefits

• Bone health and calcium absorption — vitamin D3 increases intestinal calcium absorption by 30-40%, and deficiency is a primary driver of osteoporosis and fractures
• Immune system support — a 2017 BMJ meta-analysis of 25 RCTs (n=11,321) found daily or weekly vitamin D supplementation reduced the risk of acute respiratory tract infections by 12% overall and 70% in those with severe deficiency
• Mood and depression — a 2014 meta-analysis of 7 RCTs found vitamin D supplementation had a statistically significant effect on depression, comparable to mild antidepressant effects
• Cancer risk reduction — the VITAL trial (n=25,871) found vitamin D3 at 2,000 IU/day reduced cancer mortality by 25% over 5 years in subgroup analysis
• Muscle strength — deficiency is associated with sarcopenia, and supplementation in deficient adults improves lower-body strength and reduces fall risk by 19%

What the Research Says

Vitamin D has one of the largest evidence bases of any supplement. The landmark VITAL trial (2019, NEJM, n=25,871) found that while vitamin D3 at 2,000 IU/day did not significantly reduce overall cancer incidence, it reduced cancer mortality by 25% in follow-up analysis. A 2017 BMJ individual participant data meta-analysis of 25 RCTs demonstrated that vitamin D supplementation reduced acute respiratory infections, with the greatest benefit in those with baseline 25(OH)D levels below 25 nmol/L. Bone health benefits are well-established by decades of research.

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