Vegetarians, who account for about 5% of the US adult population, do not eat meat (including poultry and seafood). The percentage of Americans who identify as vegetarian has remained steady for two decades. 11% of those who identify as liberal follow a vegetarian diet, compared to 2% of conservatives. 
Proponents of vegetarianism say that eating meat harms health, wastes resources, and creates pollution. They often argue that killing animals for food is cruel and unethical since non-animal food sources are plentiful.
Opponents of a vegetarian diet say that meat consumption is healthful and humane, and that producing vegetables causes many of the same environmental problems as producing meat. They also argue that humans have been eating and enjoying meat for 2.3 million years. 
In Western culture, vegetarianism dates back to Ancient Greece. The mathematician Pythagoras (570 BC – 495 BC) advocated vegetarianism. A meatless diet was commonly called the “Pythagorean diet” until the term vegetarian became popular during the 1800s.  The philosopher Plato (428 BC – 348 BC) described a vegetarian diet as “divinely ordained.” 
Other well-known vegetarians include Leonardo da Vinci (1452-1519), George Bernard Shaw (1712-1778), Leo Tolstoy (1828-1910), Mohandas Gandhi (1869-1948), and Franz Kafka (1883-1924).  More recent vegetarians include César Chávez, Jane Goodall, Paul McCartney, Ellen DeGeneres, Carl Lewis, Russell Brand, Pamela Anderson, and Dennis Kucinich (D-OH).
In 1850, the American Vegetarian Society was formed by Reverend Sylvester Graham (1794-1851), a nutritionist and the inventor of the Graham Cracker. The society advocated vegetarianism and avoiding white flour to promote health and cure alcoholism and lust. 
In the late 1800s, Seventh-Day Adventism a form of Christianity, was developed in the United States. The Seventh-Day Adventist Church preached and practiced vegetarianism as the most ethical, spiritual, and healthy diet. Dr. John Harvey Kellogg (1852-1953), the inventor of corn flakes, was a member.  Adventists believe God intended humans to be stewards of the creatures of the earth, not consumers of them. 
Many Quakers, Buddhists, Hindus, and Rastafarians also advocate vegetarianism as an extension of their belief in practicing non-violence. 
Vegetarianism in the United States
In 1906 Upton Sinclair published The Jungle, a popular book about Chicago’s filthy, unhygienic meat-packing facilities and their exploited immigrant workers. The book’s revelations led to a government investigation and the passage of the Meat Inspection Act and the Pure Food and Drug Act of 1906. 
In 1916 the USDA issued its first food guide, “Food for Young Children,” which included meat and milk in one of five necessary food groups for optimal health.  In 1917, during World War I, the US government advocated “Meatless Tuesdays” to conserve meat for the troops.
In the 1950s post-war prosperity caused demand for meat to increase. With little new grassland left to support expanding livestock herds, farmers began turning to grain and soy, rather than pasture grasses, to feed their animals. By 1960 US soybean production nearly tripled that of China. 
In 1958 US President Dwight Eisenhower signed the Humane Methods of Slaughter Act (HMSA) into law under opposition from the USDA and the meat industry. The law sought to minimize the pain of animals by mandating livestock be stunned unconscious before slaughter. An exemption was made for ritual slaughter under religious law. Poultry are exempt from the HMSA. 
In the 1970s US public interest in vegetarianism grew, fueled by books such as Frances Moore Lappe’s Diet for a Small Planet and Peter Singer’s Animal Liberation. In 1974, the North American Vegetarian Society was founded as was the magazine Vegetarian Times. 
In 1980, People for the Ethical Treatment of Animals (PETA) formed to advocate for a vegan diet and an end to using animals for testing, entertainment, or clothing. PETA remains one of the largest animal rights organizations in the world. 
Between 1982 and 1997, the number of animals on concentrated animal feeding operations (CAFOs) increased by 88%.  This industrialization of meat production lowered US prices and increased consumption. In 1970, Americans spent 4.2% of their income to consume 194 pounds of red meat and poultry per person. By 2005 Americans were consuming 221 pounds of red meat and poultry per person (a 12% increase) while spending 2.1% of their income on it (a 50% decrease). 
On Oct. 18, 1987, the American Dietetic Association (ADA) released its first position paper endorsing a vegetarian diet stating that, “appropriately planned vegetarian diets are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases.” 
Vegetarianism Debate in the 1990s – 2010
In the early 1990s Dr. Temple Grandin devised transportation devices, stockyards, loading ramps, and restraining systems designed to minimize stress and calm animals as they are led to slaughter.  In 1991 Dr. Grandin’s recommendations for humane animal handling and slaughter were adopted by the American Meat Institute, the oldest and largest meat and poultry trade association in the country. 
In Dec. 1995 the USDA stated for the first time  that “vegetarian diets are consistent with the dietary guidelines for Americans and can meet the recommended dietary allowances for nutrients.” 
In 1996 the Center for Consumer Freedom was formed to fight against what it termed “self-anointed ‘food police,'” and “animal-rights misanthropes.” The group lobbies for the food industry against health regulations and lawsuits, and advocates eating meat as a “personal choice.” One of its main targets has been the animal rights organization PETA. 
On Apr. 16, 1996, the Oprah Show aired a debate between former rancher Howard Lyman and Dr. Gary Weber, spokesman for the National Cattlemen’s Beef Association (NCBA). After Lyman described how dead cows were ground into feed for other cows risking the spread of mad cow disease, Oprah Winfrey stated: “It has just stopped me cold from eating another burger.” The show caused a fall in cattle futures on the Chicago Mercantile Exchange and prompted the NCBA to sue Oprah for “disparagement” of beef – a case they eventually lost.  After the Oprah controversy, the USDA implemented a ban prohibiting “the use of most mammalian protein in the manufacture of animal feed intended for cattle and other ruminants.” 
In 1999 the Weston A. Price Foundation was founded to promote the consumption of organic “nutrient-dense” foods including raw cow’s milk, butter, and meat. The foundation actively cautions people against vegetarian diets, and promotes eating meat and saturated fat for good health. 
The health benefits of their vegetarian diet were shown in a 2001 study published in the Archives of Internal Medicine. 
On Apr. 10, 2001, the Washington Post re-ignited public debate about slaughterhouses with their exposé “They Die Piece by Piece.” The investigation found that animals in slaughterhouses were often cut apart “piece by piece” while still conscious.  The public outcry that followed led Congress to earmark funds specifically for enforcing the HMSA, which the USDA used to hire a veterinarian in each of its 15 districts to oversee enforcement. In 2002 Congress passed a resolution urging the USDA to fully enforce and track violations of the HMSA. 
In 2005 Dr. T. Colin Campbell published the results of a 20-year study conducted by Cornell University, Oxford University, and the Chinese Academy of Preventative Medicine. The China Study found that people who ate the most plant-based foods were the healthiest, and that people who ate the most animal-based foods developed the highest rates of diseases such as diabetes and cancer.  However, the study was criticized in Wise Traditions, the magazine of the Weston A. Price Foundation, as “biased” with evidence “selected, presented, and interpreted,” in favor of a vegetarian or vegan diet. 
In 2006, the US market for processed vegetarian foods, such as faux meat, non-dairy milks, and frozen vegetarian entrees, was estimated to be $1.17 billion and growing. 
A 2008 Vegetarian Times poll conducted by Harris Interactive showed 7.3 million vegetarians in the US—3.2% of the total population (1 million, or 0.5%, of those vegetarians are vegan).  In most countries vegetarians are a small minority, comprising about 3-5% of the population. India is an exception where approximately 35% of the population has followed a traditional vegetarian diet for many generations.  The average American gets 67% of his or her dietary protein from animal sources, compared with a worldwide average of 34%. 
Post-2010s Polls, Studies, and Political Figures
In 2010 President Bill Clinton adopted a vegan diet (no meat, eggs, dairy, or other animal products) after his second heart surgery. In Aug. 2011 President Clinton stated, “my blood tests are good, and my vital signs are good, and I feel good, and I also have, believe it or not, more energy.” 
On June 2, 2011, Michelle Obama unveiled the USDA “My Plate” image representing the five essential food groups and replacing the previous Food Pyramid “My Plate” renamed the “Meat & Beans” category to “Protein,” and changed the “Milk” category to “Dairy.” The other three categories (Grains, Vegetables, and Fruits) remained the same.
A 2012 Gallup poll found that approximately 5% of Americans (15,695,702 people) considered themselves to be vegetarian, and 2% (6,278,281 people) considered themselves to be vegan.  Total US meat consumption in 2012 was estimated to be 165.9 pounds per person—18.1 pounds fewer than the 2004 high of 184 pounds per person. 
In Jan. 2013, the Active Learning Elementary School in the Flushing neighborhood of Queens, New York, became the first public school in the United States to serve an all-vegetarian menu in its cafeteria. 
In 2015, the World Health Organization (WHO) classified processed meats as carcinogenic to humans, and red meat as probably carcinogenic.
In 2018, Oxford University researchers estimated that red and processed meat consumption could lead to health care costs upwards of $285 billion by 2020, and be associated with 2.4 million deaths globally.
Researchers from UC Davis found that health was the most common motivation for switching to a vegetarian diet. The results of the three-year, 8,000-person study, published in Apr. 2020, found that concern about the environment and animal rights had less impact on the decision to give up meat. The authors noted that people following a plant-based diet for health reasons are also the least strict and compliant with vegetarianism. 
Impact of COVID-19 on Meat Supply
During the COVID-19 (coronavirus) pandemic, the closure of meat processing facilities due to the spread of the coronavirus led to concerns about a global meat shortage.  Beyond Meat, a plant-based meat substitute that generated over $150 million in 2019 revenue, experienced a 41% jump in stock price due to threats of a disruption in the meat supply in Apr. 2020. 
On Apr. 28, 2020, President Trump signed an Executive Order directing the US Department of Agriculture “to ensure America’s meat and poultry processors continue operations uninterrupted to the maximum extent possible.”  The Executive Order stated that closing a single large beef processing plant results in a decrease of 10 million servings of beef per day.
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