It’s worth noting that this was done in a sunny place, it would be better to test this in an a place with a darker winter, that being the reason so many people are deficient in D. What is the incidence of deficiency in the study population?
Ultimately while it would be interesting to know if CVD risk is reduced with vitamin D supplementation in those who are vitamin D deficient, it is largely an academic question as those individuals should be taking vitamin D supplements anyway.
https://wiki.cancer.org.au/skincancerstats/UV_radiation#:~:t....
https://www.ga.gov.au/scientific-topics/energy/resources/oth....