alt Hacker NewsWe're far too generous with what we allow to be called "science".
There is no dietary research, because you can't pull off an unbiased dietary study over a meaningful period of time. Practical and ethical problems abound.
Maybe one day we can simulate n=10mm people from the neck down for a period of 30 years, and feed half of them bacon and half of them beans, but even that will have the major problems of being a simulation and that only from the neck down.
Read the original "fat = heart attacks" studies by Ancel Keys from the 1950's. I've done free online 5-minute long data science tutorials with more statistical rigor.
There are ALL kinds of things we can't run experiments on. Climate, society, evolution, tech development, surgery, and more. We don't throw our hands in the air and say "science here is impossible!". Instead we roll up our sleeves and develop more and better causal inference models that improve over time.