Some people still worry about the ease with which a vegetarian diet can provide all essential nutrients. The fact is, as hundreds of millions of healthy vegetarians around the world demonstrate, it is very easy to have a well-balanced diet with vegetarian foods. Vegetarian foods provide plenty of protein; careful combining of foods is not necessary. Any normal variety of plant foods provides more than enough protein for the body's needs. Although there is somewhat less protein in a vegetarian diet than a meat-eater's diet, this is in fact an advantage. Excess protein has been linked to kidney stones, osteoporosis, and possibly heart disease and some cancers. A diet focused on beans, whole grains, and vegetables contains adequate amounts of protein without the "overdose" most meat-eaters get.

Calcium is easy to find in a vegetarian diet. Many dark green leafy vegetables and beans are loaded with calcium, and some orange juices and cereals are calcium-fortified. Iron is plentiful in whole grains, beans, and fruits.

Vitamin B12 is a genuine issue for strict vegetarians (vegans), although very easy to deal with. Traditionally, getting this vitamin has not been difficult. In cultures with plant-based diets, the microorganisms that produce B12 grow in the soil and cling to root vegetables, and traditional Asian miso and tempeh contain large amounts of the vitamin. But with industrialized production and improved hygiene, this source of B12 has been eliminated. Meat-eaters get B12 through microorganisms living in the animals they eat.

Although cases of B12 deficiency are very uncommon, it is important to make sure that one has a reliable source of the vitamin. Good sources include all common multiple vitamins (including vegetarian vitamins), fortified cereals, and fortified soymilk. It is especially important for pregnant women and breast-feeding mothers to get enough vitamin B12.

During pregnancy, nutritional needs increase. The American Dietetic Association has found vegan diets adequate for fulfilling nutritional needs during pregnancy, but pregnant women and nursing mothers are advised to supplement their diets with vitamins B12 and D. Most doctors also recommend that pregnant women supplement their diet with iron and folic acid, although vegetarians normally consume more folic acid than meat-eaters.

Vegetarian women have a lower incidence of pre-eclampsia in pregnancy, and significantly more pure breast milk. Analyses of vegetarians' breast milk show that the levels of environmental contaminants in their milk are much lower than in non-vegetarians. Studies have also shown that in families with a history of food allergies, when women abstain from allergenic foods, including milk, meat, and fish, during pregnancy, they are less likely to pass allergies onto the infant. Mothers who drink milk pass cow antibodies along to their nursing infants through their breast milk. These antibodies can cause colic.

Vegetarian children also have high nutritional needs, but these, too, are easily met by a vegetarian diet. A vegetarian menu is life-extending. As young children, vegetarians may grow more gradually, reach puberty somewhat later, and live substantially longer than do meat-eaters. Do be sure to include a reliable source of vitamin B12.