[trombonechamp]

> One of the major reasons I hold the medical and bio community is such low esteem - they don't know what they don't know yet act as if they do.

On one hand, this is due to poor science journalism. The media loves nutritional research because telling people what they are doing wrong generates clicks. It is very easy to sensationalize. "A small correlation between celery and colon cancer in a specific population from a specific region" (or whatever) in a scientific paper becomes "Celery slowly killing you, Harvard researchers prove".

One the other hand, this is how science works. We do experiments, get the results of those experiments, and try to make the best use of the data we have. Usually, the truth is much more complicated, but there are always bigger and more complicated experiments which need to be done to understand this more complicated truth. This happens all the time in all fields of science, but isn't as visible to the broader public because most research isn't all that relevant or interesting to non-scientists.

It is REALLY hard to design good (ethical) experiments in nutrition. The scientific consensus now is very different than what it will be in 10 years, because we will have more data and higher quality data. This will allow researchers to continue to incorporate more complexities and nonlinear effects. So you're right in that "linear thinking" is not ideal, but a linear model is better than no model.

[tsimionescu]

> One the other hand, this is how science works. We do experiments, get the results of those experiments, and try to make the best use of the data we have.

That is not how science works. A scientific experiment has to have enough statistical power for the claim you are trying to make. If it doesn't, then you don't make the claim.

As you say, it's extremely hard to make good (I would say even decent) nutritional studies. The vast majority of nutritional studies are not even close. Why then do dieticians pretend to be medical doctors and give advice based on these studies? Why do they give advice to entire nations based on scientific-sounding gobbledygook?

When you don't know something, the scientific thing to do is to say you don't know. Physicists don't claim they know how gravity works at the quantum level just because they have some models that sorta kinda work sometimes. A linear model of a non-linear phenomenon is not in any way better than no model - it's obviously worse.