vegetarianism, theory and practice of eating only fruits and vegetables, thus excluding animal flesh, fish, or fowl and often butter, eggs, and milk. In a strict vegetarian, or vegan, diet (i.e., one that excludes all animal products), the nine amino acids that must be supplied by the diet can be obtained by eating foods that include both grains and legumes (e.g., beans or tofu) at any point during the day. Vitamins B12 and D can be obtained through supplements or the addition of a cup of nonfat milk or yogurt to the daily diet. Ovolactovegetarians obtain complete proteins by including milk, cheese, and eggs in their diets.
The basis of the practice of vegetarianism may be religious or ethical, economic, or nutritional, and its followers differ as to strictness of observance. Certain Hindu and Buddhist sects are vegetarian, as are Seventh-day Adventists. As a general movement vegetarianism arose about the middle of the 19th cent.; it made considerable progress in Great Britain and in the United States. In the contemporary United States, vegetarianism has gained acceptance as a practice that lowers one's risk for the "diseases of affluence," e.g., high blood pressure, heart disease, diabetes, and certain cancers.
See C. Spencer, A History of Vegetarianism (1995); T. Stuart The Bloodless Revolution (2007).