In this randomized trial of oral vitamin D ₃ supplementation (60,000 IU per month) in Australians 60 years or older, no reduction in all-cause mortality was achieved by vitamin D ₃ monthly supplementation in these unscreened older people. Point estimates as well as exploratory analyses excluding the early follow-up period were consistent with an elevated risk of death due to cancer. In people who are vitamin D-replete, this dosing regimen might not be appropriate.

• Participants were randomized (1:1) to receive one oral gel capsule of either 60,000 IU vitamin D ₃ or placebo once a month for 5 years.

• Post-intervention, 1100 deaths were documented (placebo 538 [5·1%]; vitamin D 562 [5·3%]).

• For the impacts of vitamin D ₃ on all-cause mortality and cardiovascular disease mortality, the estimated hazard ratios (HRs) were 1.04 and 0·96, respectively.

• The estimated HR for cancer mortality was 1·15 and for death from other causes it was 0·83.

• The odds ratio for the per-protocol analysis was OR 1·18.

• In exploratory studies excluding the first 2 years of follow-up, a numerically higher hazard of cancer mortality was reported in those who received vitamin D vs the placebo group (HR 1·24).