This question is really several questions, don't you think? I will address the issue of diseases and conditions caused by malnutrition and over-nutrition.
Malnutrition is, as the name suggests, a state in which the body does not have vitamins, minerals, and proteins in sufficient quantity for good health or in which the body is unable to absorb these necessities in sufficient quantities. Deficiencies can result in any number of diseases and conditions, including beriberi, rickets, scurvy, pellagra and spina bifida (which results from prenatal deficiencies.) These are all diseases or conditions which can be the consequence of malnutrition. Sometimes, damage done by malnutrion is reversible, but sometimes it is not and leads to death.
The most obvious condition which over-nutrition might cause is obesity, which leads to conditions and diseases such as hypertension, heart disease, cancer, and diabetes. It is also possible to have too much of a particular vitamin or mineral. For example, too much iron causes constipation. An overdose of vitamin C can result in kidney stones or extreme cases of diarrhea.
Since there are few clear standards on what we really need in the way of vitamins and minerals, it is particularly important for a doctor to monitor the intake of supplements.
The various approaches to solving the problems of malnutrition and over-nutrition are a complexity, and I invite you to solicit responses on each of the facets you are expected to address. Good luck to you!