It depends on how you define “vegetarian”. If we are talking about an ovo-lacto vegetarian diet, which includes animal products like milk, dairy and eggs, then acquiring these nutrients is easy. A vegan diet, however, is more problematic, as the vitamin B12 is only available in animal products.
B12 is important for the formation of blood and for the normal functioning of the nervous system. Our bodies can store B12, but only for a certain period of time, so if our B12 intake is lacking, this can lead to deficiency symptoms. I would therefore strongly urge all vegans to take appropriate B12 supplements.
Gisela Olias of the German Institute of Human Nutrition Research (DIfE) in Potsdam-Rehbrücke answered this question.