There are different types of vegetarians:

Vegans exclude all animal products (e.g. meat, poultry, fish, eggs, milk, cheese, and other dairy products). Many vegans also do not eat honey.

Lacto vegetarians exclude meat, poultry, fish, and eggs but include dairy products.

Lacto-ovo vegetarians exclude meat, poultry, and fish but include dairy products and eggs.

Why are people vegetarians?
People are vegetarians for many reasons, including concern for personal health and the environment, economic and world hunger concerns, compassion for animals, belief in nonviolence, food preferences, or spiritual reasons. People may become vegetarians for one reason, and then later on adopt some of the other reasons as well.

Environment

Most people don't think of diet as an environmental issue, but it is! Meat production is incredibly inefficient. By growing grain which is fed to livestock which is fed to humans, you end up with much less food than you would have by feeding grain and other plant products directly to humans. Annually, an acre of land can produce 40,000 pounds of potatoes, 50,000 pounds of tomatoes, or a paltry 250 pounds of beef.

If Americans would reduce meat consumption by just 10%, enough grain would be saved to feed the 60,000,000 people who die of hunger each year. It's a damn shame that people in third-world countries are going hungry while their land is being used to feed meat to rich people in other countries.

The grain used for livestock feed puts a heavy burden on the land and is responsible for most topsoil depletion. Topsoil depletion is a serious problem in today's world, and it's also historically responsible for the demise of many great civilizations. Will we be next?

What are the health benefits of a vegetarian diet?

Are there any health risks in becoming a vegetarian?
Though being a vegetarian can be a healthy lifestyle, care needs to be taken that this is not a step towards a generally more restrictive, disordered eating pattern. Be sure you fully understand why you are choosing vegetarianism.

Do vegetarians get proper nutrition?
The key to any healthy diet is to choose a wide variety of foods, and to consume enough calories to meet your energy needs. It is important for vegetarians to pay attention to these five categories in particular.

Protein
Protein is found in both plant foods and animal foods. It is NOT necessary to combine specific foods within a meal in order to "complete" the amino acids profile of the proteins found in plant foods. Eating a wide variety of foods and enough calories during the day will fulfill your protein needs. Good sources of protein include whole grains, lentils, beans, tofu, low-fat dairy products, nuts, seeds, tempeh, eggs, and peas.

Calcium
Vegetarians can meet their calcium needs if they consume adequate amounts of low-fat and fat-free dairy products such as milk, yogurt, and cheese. Calcium is also found in many plant foods including dark, leafy greens (e.g. spinach, kale, mustard, collard and turnip greens, and bok choy), broccoli, beans, dried figs, and sunflower seeds, as well as in calcium-fortified cereals, cereal bars and some juices.

Vegans (people who don't eat any animal products) must strive to meet their daily calcium requirements by regularly including these plant sources of calcium in their diets. Many soy milk products are fortified with calcium, but be sure to check the label for this. You can also include a calcium supplement in your diet, which is available at the pharmacy in Health Services.

Vitamin D
Vitamin D helps your body absorb and use calcium. There are few foods that are naturally high in vitamin D, though. Therefore, dairy products in the US are fortified with vitamin D. Many soy milk products are also fortified with vitamin D. Your body can make its own vitamin D, but only when the skin is exposed to adequate sunlight (but that can have its own risks). People who do not consume dairy products and who do not receive direct exposure to sunlight regularly should consider taking supplemental vitamin D. This supplement should contain no more than 100% of the Recommended Daily Value, however, because larger doses can be dangerous. Both multivitamin supplements and calcium supplements with vitamin D are available at the pharmacy in Health Services.

Iron
Iron-fortified breads and cereals, dark green vegetables (e.g. spinach and broccoli), dried fruits, prune juice, blackstrap molasses, pumpkin seeds, sesame seeds, and soybean nuts are good plant sources of iron. Consuming foods high in vitamin C, such as citrus fruits or juices, tomatoes, and green peppers helps your body absorb iron from these plant sources. Cooking food in iron pots and pans will also add to your iron intake.

Vitamin В₁₂
Vitamin В₁₂ is produced in animals and by bacteria in the soil. Vegetarians who consume dairy products and/or eggs usually get enough Vitamin В₁₂ since it is found in these foods. Vegans, however, should add Vitamin В₁₂ fortified soy milk to their diets. Regularly taking a broad-spectrum multivitamin and mineral supplement (available at the pharmacy in Health Services) will also supply the necessary amount of В₁₂.

What about athletes?
Being both an athlete and a vegetarian can be challenging, especially for vegans. It can be difficult to eat a volume of food high enough to meet an athlete's high caloric needs. Vegetarians who participate in sports should be aware of their increased energy needs, and should make a concerted effort to consume sufficient calories. Although there are a lot of vegetarian athletes: Andreas Cahling, 'Mr International' bodybuilder; Ruth Heidrich, Ironman triathlete, age-group record holder; Martina Navratilova, tennis champion; Stan Price, world-record holder in bench press; Debbi Lawrence, Olympic race walking champion; Billie Jean King, tennis champion; Al Oerter, discus thrower and winner of four Olympic gold medals; Dave Scott, six-time Ironman triathlon winner etc.