Summarize this article in one sentence.
Marginal zinc deficiency is relatively common, with about 2 billion people worldwide affected. Marginal deficiency results in poor growth, poor physical and mental development, and increased risk of infections. There are a number of risk factors for marginal zinc deficiency including:  Premature and low-birth-weight infants or older breast-fed infants and toddlers who do not get enough zinc-rich foods Children and adolescents Pregnant and breastfeeding women, especially younger women Patients receiving a form of intravenous feedings known as total parenteral nutrition Malnourished or undernourished children and adults People with severe or chronic diarrhea Individuals with malabsorption syndromes or digestive and liver disorders People with Celiac disease, short bowel syndrome, Crohn's disease, ulcerative colitis Alcoholics with alcoholic liver disease Individuals with chronic renal disease and sickle cell anemia Older adults (over 65 years) Individuals on specific medications that interfere with the absorption or function of zinc Strict vegetarians Severe zinc deficiency is relatively rare. It is usually the result of a rare genetic disease called acrodermatitis enteropathica. In these cases, symptoms include slow growth and development, delayed sexual maturation, skin rashes, severe diarrhea, deficiencies of the immune system, poor wound healing, poor taste sensation and poor appetite and clouding of the cornea. If you believe you have this disease, go see your doctor for tests. Though zinc is important for your body’s overall health, you want to make sure you get the right amount. It is difficult to overdose with food alone — usually an overdose occurs from taking too many supplements and/or taking supplements in addition to a high-zinc diet. Excess zinc can cause significant health problems including nausea, vomiting, loss of appetite, cramps, diarrhea and headaches.  High levels of zinc can interfere with copper and iron levels and this can cause copper and iron deficiency anemias. Always talk to your doctor and be aware the some multivitamins may include zinc.
Identify the risk factors of a zinc deficiency. Recognize the dangers of a severe zinc deficiency. Understand the dangers of too much zinc.