Do vitamin D supplements prevent cancer or heart disease?

What does the research say?

Taking 2,000 IU of vitamin D a day for around five years didn’t lower rates of cancer or major cardiovascular events in generally healthy adults. That doesn’t mean vitamin D is unimportant — it’s essential for bone and muscle health — but it suggests supplements aren’t a general preventive for these diseases in people who aren’t deficient.

The science

This arm of the VITAL trial compared vitamin D3 with placebo. Neither invasive cancer (HR 0.96) nor major cardiovascular events (HR 0.97) were significantly reduced.

In the UK, where sunlight is too weak for skin synthesis from roughly October to March, public health advice is that everyone should consider 10 µg (400 IU) a day in autumn and winter.

Key findings

• No significant reduction in invasive cancer incidence.
• No significant reduction in major cardiovascular events.
• Supplementation was well tolerated at this dose.

Limitations

• Most participants were not vitamin D deficient at the start.
• US population — sunlight exposure and diet differ from the UK.
• Doesn’t address bone, muscle or immune outcomes, where vitamin D has established roles.

References

1. Manson JE, Cook NR, Lee IM, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. N Engl J Med. 2019;380(1):33–44. doi.org/10.1056/NEJMoa1809944
2. SACN. Vitamin D and Health. 2016. www.gov.uk/government/publications/sacn-vitamin-d-and-health-report