Vitamin D supplements are really only recommended for people who cannot make their own vitamin D or obtain vitamin D from their diet. These are people who are lactose intolerant, or have darker skin or can't absorb fats (vitamin D is a fat soluble vitamin). otherwise, you obtain the best forms of vitamin D through sun exposure or diet.
Science is built on revision of existing information. That information might be plausible one day and then shown to be incorrect the next. That is science and, unfortunately, is not what the public wants to hear. The public wants definitive answers and that is not what science does. However, if a scientist publishing misleading or false information on purpose, that becomes a problem. There are "watchdog" scientists out there that search for misleading and false information. When a journal finds that a publication contains misleading or false information, the journal retracts the article and publishes notice of the retraction.