Well... with sugar for example we know for a long time that there is only about 50deciliters*80mg/DL=4grams of glucose in blood in average healthy adult. As people are eating tons of sugar a day (snickers bar has 27g, half a liter of cola has ~50g, half of it fructose but still) it's clear stuff doesn't just go into bloodstream as we would all die before finishing that snickers bar. Somehow though fat magically getting into blood and clogging arteries was something which was accepted as common sense. I do blame policy makers and scientists as healthy amount skepticism was clearly missing.