RCT: Oral Vitamin D supplementation (60.000 IU per month) did not reduce mortality in patients 60 years or older (unscreened individuals in Australia, many without insufficiency, average 30ng/mL). Exploratory analyses pointed towards an increased risk of death from cancer.

The D-Health Trial: a randomised controlled trial of the effect of vitamin D on mortality – The Lancet Diabetes & Endocrinology (link to abstract – $ for full-text)

Related:

Randomized Trial: Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease

Meta-Analysis: Vitamin D Not Effective for Cardiovascular Disease Prevention

Association between vitamin D supplementation and mortality: systematic review and meta-analysis – The BMJ

USPSTF Draft Statement: Insufficient evidence to recommend multivitamin supplements for the prevention of CVD or cancer. The statement also recommends against the use of beta-carotene (increases risk of CVD mortality and lung cancer) or vitamin E (clear evidence of no benefit)

Vitamin D, calcium, other vitamins, and supplements do not prevent cardiovascular diseases

Research: Circulating vitamin D concentration and risk of seven cancers

Research: Vitamin D and risk of total and site specific cancers