Your scenario is the one with no bearing in reality. In the western world, we do not suffer from a lack of calories from macro-nutrient deficiency. There are, however, people who suffer from micro-nutrient deficiency along with a mountain of research that micro-nutrient supplementation is inferior to consuming adequate micro-nutrients in diet. Research about declining micro-nutrient levels in staple crops is both important and more applicable to daily life than whatever non-sense you are imagining with vegans and carrots.