I’m not sure that it’s safe to say “the majority” of medical research is wrong, but there is a strong push to publish or perish at most academic medical centers. This drives people to put together and publish studies which many times are small, underpowered, or dedicated to disproving a previous study just to get their names in print. Academia has made it so that publishing is even a requirement to graduate from a medical residency.
Add to this the fact that at least some percentage of physicians at these centers are dyed-in-the-wool liberals who do not hesitate to incorporate things like cost-per-life-year-saved into their studies when making recommendations and you have a receipe for a lot of bad science.
My personal policy is to reject any single study that goes against what I know to be true about human physiology and treat patients on an individual basis as I see to their personal well being without trying to play Obamacare cop.
But I’m old school like that.
I could be wrong but I would think that most medical research isn't done in academia.