Don’t give vitamin D supplements to people who already have enough
Two large trials looked at this issue. One involved 26,000 participants who took supplements for five years; the other included 21,000 older adults on supplements for the same period. For people who already had adequate vitamin D levels, there was no change in cancer rates, cardiovascular problems, or overall mortality — the death rates were 5.3% versus 5.1% respectively. This does not apply to people who truly lack vitamin D, those with osteoporosis, or anyone who rarely gets sunlight; they should follow their doctor’s advice.
Roughly 0.2 to 0.5 yuan per day, or 100 to 200 yuan per ye…
The VITAL trial followed 25,871 participants who took 2,000 IU of vitamin D daily for 5.3 years on average. No…
Roughly 0.2 to 0.5 yuan per day, or 100 to 200 yuan per year. That’s not much money, but the real cost is the false sense of security it gives — the belief that you’ve already taken preventive steps.
The VITAL trial followed 25,871 participants who took 2,000 IU of vitamin D daily for 5.3 years on average. No difference emerged in cancer rates, cardiovascular issues, or overall mortality. For cancers likely to spread, the hazard ratio was 0.96 (a range of 0.88–1.06), meaning no real effect. Similar results appeared for major cardiovascular events and overall death rates. The absolute value of this effect is 0.93. The D-Health trial involved 21,315 Australians over 60; they received 60,000 IU monthly for five years, yet saw no meaningful change in mortality or other outcomes. The apparent benefit often stems from studies that only observe low vitamin D levels without intervention, mistakenly concluding that supplementation helps.
Manson JE et al. (2019). Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. NEJM. https://doi.org/10.1056/NEJMoa1809944；Neale RE et al. (2022). The D-Health Trial: a randomised controlled trial of the effect of vitamin D on mortality. Lancet Diabetes Endocrinol. https://doi.org/10.1016/S2213-8587(21)00345-4
Open source linkThese trials specifically excluded people with proven vitamin D deficiency, so their findings apply only to those already getting enough. Individuals who truly lack vitamin D, have osteoporosis, rarely get sunlight, or are infants still need proper medical guidance. This analysis focused solely on overall mortality, cancer, and cardiovascular health; other effects were not examined.