Something I didn't realize until my PhD daughter told me just a couple of months ago: I was already aware that a medical degree with a license to practice medicine is NOT the same as a doctorate degree, but I didn't realize that PhDs (philosophical doctors) are the original ones to earn the title "Doctor". I don't know the history behind how it happened, but she said that the term doctor in reference to a medical degree is only a courtesy title, not a mark of anything remotely like what it takes to earn a PhD.
[I should mention that she earned her PhD in the UK, so I base my description on what she went through - some of the terminology I use, and some of the steps involved may be slightly different in the US, or other countries, depending on what that country's PhD process requires.]
The PhD candidate is required to spend years doing their own research into a specific aspect of their subject matter (the topic itself being specific enough that it is different in some way from every other accepted PhD thesis), write a well documented thesis, then defend their research and conclusions in front of a panel of PhDs experienced in that general topic. Their thesis will be judged not only on the quality and completeness of their research, but also on how well they are able to defend their work - and most importantly, on how thoroughly their research supports their conclusion. Personal bias on a topic has no place in the work of a PhD thesis - it is to be based purely on research, so if you really don't like the conclusions your research proves, probably best to switch to a different topic, because there's no way you can adequately defend conclusions that are not supported by thorough research. If the thesis is deemed acceptable, it may or may not require some minor revisions, or it may require major revisions before being fully accepted. If the thesis is not acceptable because the research is inadequate, or the conclusions are not fully supported by the research, or the entire work can not be properly defended, the PhD candidate will be told to start over. Once a fully acceptable thesis is submitted, properly defended, and fully accepted, it will then be printed and held in the British Library. (the equivalent in the US would be the Library of Congress)
This is vastly different from how a medical degree is obtained. In order to become a medical doctor, they basically do a few extra years of schooling, doing the exact same thing as we all did in school - memorize a bunch of information well enough to recall information as required. Considering that a medical degree is considered to be a scientific degree, it's a travesty that they aren't required to do any more than memorize a bunch of already accepted "medical facts", and as someone pointed out, even if you're doing "scientific research", if your science experiment doesn't show the expected results, then it's automatically assumed that you did something wrong during the experiment. [Which is the exact opposite of what I was taught in 7th grade science - your experiment results are what they are. It doesn't matter if your results conform to the expected results - you record exactly what happened when YOU performed the experiment.] For all intents and purposes, the job of a physician just involves regurgitating the currently recommended drugs, procedures, and diet to every patient who comes their way. (This might be a good time to mention that for hundreds of years, balancing "humors" by bleeding patients - even those who had an injury that resulted in massive blood loss -was the medical treatment of choice for all ills) Even the so called peer-reviewed research and articles that are published in medical journals are not scrutinized nearly as thoroughly as a PhD thesis will be, because their conclusions can and often are accepted, even when they're in direct opposition to what their research proved.
Ironically, most PhDs are not awarded in subject areas that have anything to do with health - there's history, language, Literature, media, communications, mathematics, and many more non-health related PhD areas, even though their research and conclusions have nothing to do with the health and well being of millions of people. But just think if our health research related scientists actually did research the same way that a PhD candidate is required to research, write, and defend their thesis - we might actually have properly conducted research, with honest conclusions, resulting in truly sound advice regarding diet, medications, and procedures.