We all know about the deficiencies non-veg kids and adults risk, but here's a new study about began and vegetarian children:
Clinical practice: vegetarian infant and child nutrition PMID: 21912895, Dec 2011
The aim of this review is to give insight on the benefits and risks of vegetarianism, with special emphasis on vegetarian child nutrition. This eating pattern excluding meat and fish is being adopted by a growing number of people. A vegetarian diet has been shown to be associated with lower mortality of ischaemic heart disease and lower prevalence of obesity. Growth in children on a vegetarian diet including dairy has been shown to be similar to omnivorous peers. Although vegetarianism in adolescents is associated with eating disorders, there is no proof of a causal relation, as the eating disorder generally precedes the exclusion of meat from the diet. A well-balanced lacto-ovo-vegetarian diet, including dairy products, can satisfy all nutritional needs of the growing child. In contrast, a vegan diet, excluding all animal food sources, has at least to be supplemented with vitamin B(12), with special attention to adequate intakes of calcium and zinc and energy-dense foods containing enough high-quality protein for young children. The more restricted the diet and the younger the child, the greater the risk for deficiencies.