alt Hacker NewsAs a complete non-expert, as far as I can tell, the only true agreement out there is that certain very specific substances are bad for you if you consume them too often. That's tobacco, alcohol, painkillers...and that's about it for consensus ones, with alcohol having wiggle room among the public thanks to some poor studies.
Just about every other piece of nutrition advice out there can easily be categorized as controversial. Not in the sense that one side is obviously stupid or malicious, but in the sense that both sides earnestly think they are right.
> that certain very specific substances are bad for (for the general population) if you consume them too often
There are people who smoke their entire lives, die at 90, and tobacco had nothing to do with their individual deaths or even really any tangible negative health outcomes. There are people who drink or smoke pot every day and it has nothing to do with their deaths or quality of life. There are people who have steak and eggs cooked in butter every morning with no cholesterol or cardiac problems.
As a whole, people who do these things have a statistically higher probability of having negative outcomes. On an individual basis, there is a lot of variation as to what the actually effect might be.