Your biggest complaint seems to be that nobody is using sample sizes that are large enough to satisfy you. What is your justification for setting the bar so high? Just what kind of confidence levels are you looking for before you think a public health intervention is justified? 10 million people may be only 0.14% of the world population, but the total size of the world population has basically nothing to do with what constitutes a healthy diet for most people - human biology hasn't changed much in the past 300 years even though the population grew by a factor of 10. Huge sample sizes are only necessary if you're trying to study something rare (which is almost by definition not public health), or if the population is very inhomogeneous: an assumption you're making without supplying much evidence.

And the first two paragraphs of your comment read like a conspiracy nut's rant. It significantly lowers your credibility and quite justifies downvoting you for making assertions that contradict scientific consensus without providing any supporting evidence.