Went to lecture of Michael Pollen Jan 18 2012, he mentioned how
difficult it is to get good food intake info from people, to help
decide scientifically what makes a good or bad diet (though it's
generally known that modern western diet leads to more heart disease
and cancers than traditional asian, african or european diets.

Part of the problem is the "Food frequency questionnaire" which asks
rather specific information about food intake *in the last month*.