Observational studies are not completely devoid of value. They are in many cases the only way we can practically learn about certain aspects of our world.
Randomized controlled trials are better, of course.
Randomized controlled trials are better, of course.
Even if you think epidemiological methods are sound, at best they can only generate hypotheses that then need to be tested in clinical trials. Instead, these hypotheses are often prematurely trumpeted to the public as implicit fact in the form of media headlines, dietary guidelines, and well-placed commission reports like this one.
Tragically, more than 80%(3) of these guesses are later proved wrong in clinical trials. With a failure rate this high, nutrition epidemiologists would be better off flipping a coin to decide which foods cause human disease.
(1) https://www.frontiersin.org/articles/10.3389/fnut.2018.00105... (2) https://jamanetwork.com/journals/jama/fullarticle/2698337 (3) https://rss.onlinelibrary.wiley.com/doi/full/10.1111/j.1740-...
Ref: https://www.psychologytoday.com/us/blog/diagnosis-diet/20190...