Vitamin D

What the evidence says

Vitamin D is required for calcium absorption and normal bone mineralization. Correcting a documented deficiency or meeting nutritional requirements is different from taking extra vitamin D as a general anti-aging intervention.^[1]

The VITAL trial randomized 25,871 midlife and older U.S. adults to 2,000 IU of vitamin D3 daily or placebo for a median 5.3 years. Supplementation did not significantly reduce invasive cancer, major cardiovascular events, or all-cause mortality in this generally healthy primary-prevention population.^[2]

A prespecified VITAL fracture study likewise found no reduction in total, nonvertebral, or hip fractures. This result does not address treatment of severe deficiency, osteoporosis, malabsorption, or other clinical indications that were not the trial question.^[3]

Across 52 randomized trials, a 2019 meta-analysis found no significant reduction in all-cause mortality with vitamin D alone. Later analyses have produced small, sensitive mortality signals, so the most defensible conclusion is that any general-population survival effect is uncertain and not a reason to self-prescribe high doses.^[4][1]

Dose pattern matters. A meta-analysis of intermittent or single high-dose regimens found no fracture or fall prevention and a possible increase in falls. More is not necessarily better, especially when baseline status and indication are unknown.^[5]