Following a vegetarian diet, as long as one is educated properly about it, can be healthier and more beneficial to a person's overall health. I see it frequently--people becoming vegetarians, claiming that they are healthier for it; but I see them loading up on pasta, chips, and other processed garbage, and still not eating a diet high in fruit, vegetables, unprocessed and non-GMO grains, lentils, beans, nuts, and seeds....If it is not properly followed, a vegetarian/vegan lifestyle can harm one's health.
I, for one, am almost completely vegan, but I make sure I find other ways to get my B12, zinc, and iodine; these are very common deficiencies seen in vegans and vegetarians who may actually eat a pretty balanced diet.
It is good to get these nutrients, either by supplementation or by use of nutritional yeast in foods. There are also some herbs that secretly contain the very important vitamin B12. It is a common misconception that this vitamin is only in red meat - you just have to do a little research, is all. :)
Bacteria from the soil of some plants consumed by herbivorous animals that people eat contain B12, but we wash our produce so much now, that this is essentially lost. The best bet for Vegetarian/ Vegan people is to find an organic/natural supplement and to take one about every other day or so with meals.
B12 is the one water soluble vitamin that is stored in the liver for many years, which is why it sometimes takes a while for vegans/vegetarians to show deficiency. (we don't want to get to deficiency, because that will cause us problems and could be deadly) This is why you do not need it every day.
People today are going overkill on supplements, which makes me believe that it could be doing more harm than good; thus, it is important to listen to your body as well as to take in a healthy balanced diet for optimal health. :)
Nutritional Science - Dietetics B.S. Candidate, Dec., 2012
Naturopathic Medical Student Candidate, 2013