I think the established diet "authorities" could have the following position on this, which is ligitimate from their point of view I guess. Al kind of cohort studies do point towards the direction that saturated fats are bad. We all know that cohort studies have some level of inaccuracy due to not being able to correct for a lot of other parameters that have a lot of influence besides just the one that is measured. Furthermore, these types of studies are able to conclude on correlation, not on causation. On the other hand, the studies that do test for causative relations are limited since they are executed on subjects (in vivo) that are not human, resulting in an extrapolation difficulty towards human applicability. Cell level studies do have even more distance as seen from practical human perspective.
Another issue that is important is the genetic make-up of humans (or any other species for that matter). In animal studies, as far as I do understand (I'm not a bio-professional), "standardised" animals, in most cases mice, are used to create a population of subjects that are consistent in their genetic make-up. That way, the problem of statistical insignificant results (like in normal cohort studies) due to genetic variation can be corrected, but at the same time it still does not increase the possibility to extrapolate to a practical human like you or me.
So, both forms of studies do have their problems and if looked at it without any level of subtlety, none of these types of studies are applicable to our daily individual lives.
So, what do we take for granted? It's my opinion that all types of studies should be taken into account in deciding to try a diet or supplement. If you find something worthwhile to try, do it, but monitor your health up to a affordable level. It all comes down to the level of risk you are willing to take to pursue your health. It's a remarkable and interesting paradox; taking risk to increase your health. If you go with the flow, you know as an approximate mean where you will end. If you do not go with the flow, you do step outside the box, resulting in disbelieve and ridicule. But you do ow it to yourself to be aware of the risks and deal with them, i.e. to take measures against them. Like doing blood work periodically. Or sign up with a genetic service to find out as soon as possible how the statistics should be bended towards your individual genetic constitution. The problem however, is that not much diet related data is available as of yet.
Back to the average doctor, that in addition to the "stay within the box" forces from the medical environment he is in, also has a fear for being sued if he gives a bad advice. Do not expect anything progressive from that area, just use them to your advantage. And, if possible, try to find the intelligent ones that unfortunately are the exception.