Yes of course it's expensive which is why I said we should have larger scale studies with more test subjects funded by the government.
Also, what does subject reported data have to do with RTCs? What are you even arguing about?
If you have a better approach for study design then I'm sure nutrition researchers would love to hear it.
Yes, to do a proper RCT you need to confine and monitor subjects in a controlled environment. YOU used the word "years" and nobody ever suggested a study that long. If you're implying that you need a study that long to gather meaningful results then that's just simply not true.
Let me put this plainly, you can design RCTs that are:
A) Safe for participants.
B) Aren't too long.
C) Don't rely on subject reported data.
D) Still give meaningful results.
These are not mutually exclusive and they are done all the time. These are gold-standard experiments in the nutrition field.
Like you said, they are expensive to do and usually only have a small number of subjects. That's why I'm suggesting that wealthy governments should collaborate to fund massive-scale trials at maximum quality.
Best of luck to you. I'm out.
Yes, it is relatively expensive, but not prohibitively so.