[can16358p]

If the samples are TRULY random and not within a specific culture/society I doubt we need that. But whether it is is another question.

[loeg]

This is a self-report survey about historical diet. It's basically meaningless regardless. People that think they're healthy will report that they ate a lot of foods they currently think are healthy, not what they actually ate. This is true even if people are asked days later, much less years.

[YetAnotherNick]

Even if the sample is truly random, this is not a controlled study and there are correlated behaviour.