Disseminating nutrition information, along with hygiene practices, are a huge public health measure.
Long ago, I worked as a tech for a research physician. He came into the lab once and described a guy he encountered on Grand rounds who came in with scurvy. He was, as they say, a well-developed and will nourished young man, but he also pretty much only ate his favorite foods. Those foods did not include a lot of vegetables, and over time he was deficient in vitamin C.