Key points from article :
Study tested more than 25,000 adults over the age of 50 in the US over 5 years.
Randomised controlled trial (RCT) of high-dose (50mcg) vitamin D.
No difference in the number of people who developed cancer or cardiovascular disease.
No different in deaths from any cause.
These chronic diseases can take a long time to develop.
Most people had vitamin D levels above the recommended level at start of study.
The study was published in The New England Journal of Medicine.