What is they have diabetes or heart disease? Or even pre-diabetic. That covers something like 3/4 of us.True, you dont want to store just 3 months of noodles and nothing else. But the vast majority of nutrition deficiencies are not going to happen on the short term when emergency food would be used.
The vast majority of people do not have vitamin deficiencies or other significant nutritional deficiencies at baseline. Many of us eat pretty unhealthy as it is, but even a lot of junk food is fortified. So scurvy, beriberi, rickets, pernicious anemia etc are going to be many months away.
So what most people will need during SHTF is a lot of calories and clean water.
So looking at my storage which is mostly mountain house, eating any of those for 2-3 months is not going to cause any significant health issue that normally would be attributed to a "unhealthy diet"