We have had this question for some time as to whether supplementation with vitamin D helps to prevent heart disease and cancer. In the past years, some research studies reported lower rates of death from heart disease and cancer in regions with greater sun exposure than in those with less sun exposure . However, there was no firm data until now.
The New England Journal of Medicine published the result of the Vitamin D and Omega-3 Trial (VITAL), a large-scale clinical trial, early this month. The trial included 25,871 participants with an average 5.3-year follow-up, which is considered the largest and longest duration in this topic .
What they found
No difference in the incidence of cardiovascular disease or cancer among people who received and not received supplemental vitamin D 2,000 IU per day, regardless of their baseline vitamin D levels.
Where do we go from here?
While there is no added benefit from taking extra vitamin D, it is still crucial to maintain your normal vitamin D level. Prior studies recommend maintaining 25-hydroxyvitamin D at the following levels:
- > 20 ng/mL for bone and overall health 
- > 20-25 ng/mL for cardiovascular health 
- > 30 ng/mL for lower risk of colon cancer 
The Recommended Dietary Allowance (RDA) for vitamin D is 400–800 IU per day depending on your age group . But don’t forget that not only supplementals, you also get vitamin D from sun exposure and food such as fatty fish (salmon, tuna, mackerel etc), milk and egg yolks.
In conclusion, eating healthy and getting enough exposure to sunlight should be sufficient to fulfill your body need of vitamin D. However, if you are unable to do so, it is reasonable to take a standard dose of supplemental vitamin D.
Furthermore, having 25-hydroxyvitamin D level checked is another way to ensure you have the healthy level. We recommend it especially if you have symptoms that might be from vitamin D deficiency.
 Manson JE, Bassuk SS, Lee IM, et al. The VITamin D and OmegA-3 TriaL (VITAL): rationale and design of a large randomized controlled trial of vitamin D and marine omega-3 fatty acid supplements for the primary prevention of cancer and cardiovascular disease. Contemp Clin Trials. 2012 Jan;33(1):159-71.
 Manson JE, Cook NR, Lee IM, et al. Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. N Engl J Med. 2018 Nov 10.
 Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.Read More
 McCullough ML, Zoltick ES, Weinstein SJ, et al. Circulating vitamin D and colorectal cancer risk: an international pooling project of 17 cohorts. J Natl Cancer Inst 2018 June 14.