From what we have seen, we already know that Vitamin D levels and Vitamin D Deficiency have a profound effect on our health and on the efficiency of how our bodies function. It seems that for many, more proof is needed so thankfully, there are plenty of studies in the works.
Caution should be exercised when researching Vitamin D studies on the internet. We don't always know who is behind a study or how it is being funded. Some studies are paid for in order to find a specific conclusion. A company may pay for a study so that it will find in their favor. In order to do this, the research may not include all parameters. For example, if you only give participants a very low amount of Vitamin D3, a study may conclude that Vitamin D3 is not helpful.