According to the earliest documents, historical development of vegetarianism started in the 6th century BC in ancient India and ancient Greece. The diet was closely hooked up to the idea of unharmed animals and was encouraged by religious groups and philosophers in both instances.

Vegetarianism is the practice of abstaining from the consumption of meat (red meat, poultry, seafood, and the flesh of any other animal), and may also include abstention from by-products of animal slaughter.

Vegetarianism may be adopted for various reasons. Many people object to eating meat out of respect for sentient life. Such ethical motivations have been codified under various religious beliefs, as well as animal rights advocacy. Other motivations for vegetarianism are health-related, political, environmental, cultural, aesthetic, economic, or personal preference. There are variations of the diet as well: an ovo-lacto vegetarian diet includes both eggs and dairy products, an ovo-vegetarian diet includes eggs but not dairy products, and a lacto-vegetarian diet includes dairy products but not eggs. A strict vegetarian diet – referred to as vegan – excludes all animal products, including eggs and dairy. Avoidance of animal products may require dietary supplements to prevent deficiencies such as vitamin B12 deficiency, which leads to pernicious anemia. Psychologically, preference for vegetarian foods can be impacted by one’s own socioeconomic status and evolutionary factors.

There are many different reasons for adopting a vegetarian lifestyle. Almost all people believe in the benefits of a vegetarian diet, this section will show the health and environmental advantages. First of all, it brings some positive impacts on health. In the article ‘Health benefits of a vegetarian diet’, the author, Mary Krane Derr, supports the advantages of vegetarian diet on reducing disease risk. There are more “phytochemicals”, “plant compounds with many known antioxidant and other cancer-reducing properties” in any vegetarian diet. Moreover, a vegetarian diet “reduces the risk for heart disease, type 2 diabetes, kidney disease, high blood pressure, reduces rates of overweight, obesity and less dementia and other serious diseases”, which make people become healthier and live for a longer time. With much scientific information, Derr’s statements make it extremely clear about benefits when becoming a vegetarian. Changing a vegetarian lifestyle is a good way to keep healthy and avoid serious diseases.

Another benefit of vegetarian diet is conserving environment. According to a 2009 Californian study comparing the environmental impacts of vegetarian versus non-vegetarian diet, the researchers found that a non-vegetarian diet consumed 2.9 times more water (Mach, 2000), 2.5 times more primary energy, 13 times more fertilizer, and 1.4 times more pesticide than a vegetarian diet (Marlow et al. 2009). Another Italian study presented in the European Journal of Clinical Nutrition evaluating the environmental effects of omnivorous and vegetarian diets gave the same results. They concluded that meat diets strain the environment too much and pointed out that water-consuming, in particular, played the most essential role by accounting for 41-46% of the overall effect. As a result, it is very clear that any vegetarian diet contributes to reducing the amount of water, energy, fertilizer, and pesticide, which tends to protect our environment.

Studies on the health effects of vegetarian diets observe mixed effects on mortality. One review found a decreased overall risk of all-cause mortality, cancer (except breast), and cardiovascular disease; however, a meta-analysis found a lower risk for ischemic heart disease and cancer but no effect on overall mortality or cerebrovascular disease. Possible limitations include varying definitions used of vegetarianism and the observation of increased risk of lung cancer mortality in those on a vegetarian diet for less than five years. An analysis pooling two large studies found vegetarians in the UK have similar all-cause mortality as meat-eaters.

The American Dietetic Association has stated that at all stages of life, a properly planned vegetarian diet can be “healthful, nutritionally adequate, and may be beneficial in the prevention and treatment of certain diseases.” Vegetarian diets offer lower levels of saturated fat, cholesterol and animal protein, and higher levels of carbohydrates, fiber, magnesium, potassium, folate, and antioxidants such as vitamins C and E and phytochemicals.