The world’s largest organisation of food and nutrition professionals, the American Dietetic Association (ADA), has long-stated that appropriately-planned vegetarian and vegan diets are appropriate for people of all ages (including during pregnancy, lactation, infancy, childhood and adolescence) and for athletes. In an updated paper they now state how vegetarians also tend to have lower levels of cholesterol, blood pressure, type 2 diabetes, body mass index and overall cancer rates.
Craig et al., 2009. Position of the American Dietetic Association: vegetarian diets. Journal of the American Dietetic Association. 109 (7) 1266-1282.