Everyone can be vegan - just eat vegan, and maybe go further. Veganism is for everyone, in every industry, with any occupation, and situation, and any levels of awareness or ethics. Calling anyone "not real vegan" - especially knowing that being vegan is not a rewarding social position - is unnecessary demanding and even intimidating fashion among vegans, detrimental to the spread of veganism, imho. I observed it for years, and never witnessed anything good or productive resulting from it.
Undernutrition is a form of malnutrition. (Malnutrition also includes overnutrition).
Undernutrition can result from:
inadequate ingestion of nutrients,
loss of nutrients due to diarrhea,
increased nutritional requirements.
Undernutrition progresses in stages: it may develop slowly when it is due to anorexia or very rapidly. First, nutrient levels in blood and tissues change, followed by intracellular changes in biochemical functions and structure. Ultimately, symptoms and signs appear. Diagnosis is by history, physical examination, body composition analysis, and sometimes laboratory tests.
Undernutrition from micronutrient deficiencies, or "hidden hunger", affects over 2 billion people globally and can lead to reduced growth and cognitive development, birth defects, blindness, and overall poor health. Vitamin A deficiency, iron deficiency anaemia and iodine deficiency disorders are among the most common forms of micronutrient malnutrition.