Well now you're just making things up. Deaths from nutritional deficiency have always been extremely rare in the USA. Outside of some isolated cases of abuse or neglect or mental illness, only the poorest people ever died of malnutrition. It has never been among the leading causes of death. Knowing this or that is necessary in food is mostly just of academic interest and hasn't actually produced better health outcomes.
This is not true. The malnutrition of some kind is not rare and diseases from it were life. Malnutrition is not famine. It is lack of Iron and anemia. It is Rickets due to lacking calcium. It is missing any of vitamins - like being sickly in winter due to lack of vitamin C.
It is missing Iodine which is now commonly added to salt.
You can be overfed in calories and still suffer from malnutrition. Especially without science we have now. And whole classes of sicknesses caused by malnutrition don't exist anymore.
They used to die of malnutrition of all kinds. Not just because of being poor, but because of us not knowing this or that is necessary in food.
The physical work people used to do was body breaking fairly often. The chemicals people used to be in daily contact with were body damaging too.