But what about deficiencies?
Iron. Studies have shown that in Western countries, meat eaters and vegetarians get about the same amount of iron. But meat, particularly red meat, contains heme iron, which is much more readily absorbed than the non-heme form in plant foods. Other dietary factors affect the absorption of non-heme iron. Enhancers include vitamin C. Inhibitors include phytic acid in whole grains, legumes, lentils, and nuts; polyphenols in tea, red wine, and other food; and possibly soy protein. In the West, vegetarians do tend to have lower iron "stores" in their bodies. Some studies also indicate lower levels of hemoglobin. But vegetarians don’t have higher rates of iron-deficiency anemia, and some studies suggest that their lower iron stores may have health benefits.
Protein. Studies show that most vegetarians get the 50 grams of protein per day recommended by the FDA as part of a standard 2,000-calorie diet. Beans, dairy products, eggs, nuts, and soy have plenty of protein. Vegetarians used to be told that they needed to be careful about getting complementary proteins because plant-based proteins don’t come with all the amino acids contained in meat protein. Because most vegetarians in developed countries eat an ample supply of protein, they end up getting the full set of amino acids, so juggling foods to get complementary proteins isn’t necessary.
Vitamin B12. Dairy foods and eggs are good sources, so many vegetarians get plenty of vitamin B12. The stricter vegan diet, which doesn’t include any animal-based foods, could theoretically lead to a shortage of B12. The vitamin is added to several brands of breakfast cereal (Total, for example) as well as some brands of soy milk. Note, though, that many "natural" health-food cereals are not fortified with any vitamins, including B12.