A plant-based diet is a diet consisting mostly or entirely of foods derived from plants, including vegetables, grains, nuts, seeds, legumes and fruits, and with few or no animal products. A plant based-diet is not necessarily vegetarian. The use of the phrase plant-based has changed over time, and examples can be found of the phrase "plant-based diet" being used to refer tovegan diets, which contain no food from animal sources, to vegetarian diets which may include dairy or eggs but no meat, and to diets with varying amounts of animal-based foods, such as semi-vegetarian diets which contain small amounts of meat. The Academy of Nutrition and Dietetics issued a position statement proposing that well-planned plant diets support health and are appropriate throughout life, including pregnancy, lactation, childhood, adulthood, and for athletes. As of the early 21st century, it was estimated that four billion people live primarily on a plant-based diet, some because of limits caused by shortages of cropland, freshwater, and energy resources. In Europe, consumption of plant-based meat substitutes was 40% of the world market in 2019, with sales forecast to grow by 60% through 2025 due mainly to concerns for health, food security, and animal welfare. In the United States during 2019, the retail market for plant-based foods was growing at eight times the rate of the general retail food market.
Terminology
Vegan author Ellen Jaffe Jones stated in a 2011 interview: Several sources use the phrase plant-based diet to refer to diets including varying degrees of animal products, defining "plant-based diets" as, for example "diets that include generous amounts of plant foods and limited amounts of animal foods", and as diets "rich in a variety of vegetables and fruits, legumes, and minimally processed starchy staple foods and limiting red meat consumption, if red meat is eaten at all". Others draw a distinction between "plant-based" and "plant-only". In various sources, "plant-based diet" has been used to refer to:
Veganism: diet of vegetables, legumes, fruit, grains, nuts, and seeds, but no food from animal sources.
Vegetarianism: diet of vegetables, legumes, fruit, nuts, and grains, that may include eggs and dairy, but no meat.
* Ovo-lacto vegetarianism: includes dairy and eggs
*Ovo vegetarianism: includes eggs but no dairy
*Lacto vegetarianism: includes dairy but no eggs
Semi-vegetarianism: mostly vegetarian diet with occasional inclusion of meat or poultry.
*Macrobiotic diet: semi-vegetarian diet that highlights whole grains, vegetables, beans, miso soup, sea vegetables, and traditionally or naturally processed foods, with or without seafood and other animal products.
* Pescatarian: semi-vegetarian diet with eggs, dairy and seafood.
* semi-vegetarian diet that includes limiting meat intake daily or being vegetarian only on certain days of the week.
History
Prehistoric life
Although herbivory was long thought to be a Mesozoic phenomenon, evidence of it is found as soon as the fossils which could show it. Within less than 20 million years after the first land plants evolved, plants were being consumed by arthropods. Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibiouspiscivores. While amphibians continued to feed on fish and insects, some reptiles began exploring two new food types: the tetrapods and plants. Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation. In contrast, a complex set of adaptations was necessary for feeding on highly fibrous plant materials.
Modern herbivores and mild omnivory
Quite often, mainly herbivorous creatures will eat small quantities of animal-based food when it becomes available. Although this is trivial most of the time, omnivorous or herbivorous birds, such as sparrows, often will feed their chicks insects while food is most needed for growth. On close inspection it appears that nectar-feeding birds such as sunbirds rely on the ants and other insects that they find in flowers, not for a richer supply of protein, but for essential nutrients such as Vitamin B12 that are absent from nectar. Similarly, monkeys of many species eat maggoty fruit, sometimes in clear preference to sound fruit. When to refer to such animals as omnivorous or otherwise, is a question of context and emphasis, rather than of definition.
Humans
Humans are omnivorous, capable of consuming diverse plant and animal foods. Fossil evidence from wear patterns on teeth indicates the possibility that early hominids like robust australopithecines and Homo habilis were opportunistic omnivores, generally subsisting on a plant-based diet, but supplementing with meat when possible.
Sustainability
The Food and Agriculture Organization defined a sustainable diet as one with ‘low environmental impacts which contribute to food and nutrition security, and to healthy life for present and future generations’, and one that is affordable for all while optimizing both natural and human resources. A sustainable diet can be measured by its level of nutritional adequacy, environmental sustainability, cultural acceptability and affordability. Environmental sustainability can be measured by indicators of efficiency and environmental protection. Efficiency measures the ratio of inputs and outputs required to produce a given level of foods. Input energy refers to processing, transporting, storing and serving food, compared with the output of physical human energy. Conversely, environmental protection refers to the level of preservation of ecological systems. Plant-based diets may contribute to reducing greenhouse gas emissions and the amount of land, water and fertilizers used for agriculture. As a significant percentage of crops around the world are used to feed livestock rather than humans, increasing the practice of a plant-based diet may contribute toward minimizing climate change and biodiversity loss. While "soy cultivation is a major driver of deforestation in the Amazon basin", most soy crops are not destined for human consumption.
Health research
Plant-based diets are under preliminary research to assess whether they may improve metabolic measures in health and disease, and if there are long-term effects on diabetes. When clinical studies were focused to the types of plant-based foods, such as fruits, vegetables, whole grains, legumes, and nuts, improvement of diabetes biomarkers, such as reduced incidence of obesity, was observed. Plant-based diets were also associated with improved emotional and physical well-being, relief of depression, quality of life, and general health in diabetic people. Cognitive and mental effects of a plant-based diet are inconclusive.
Commerce of plant-based foods
In 2019, Europeans consumed 40% of the world total of plant-based alternative meats out of concern for health, food security, and animal welfare. During 2019, the total retail market for plant-based foods in the United States was $4.5 billion, growing at 31% over the previous two years compared to 4% for the entire retail food market. Growth of plant-based food consumption in the United States occurred among flexitarian consumers seeking alternative protein sources to meat, fortification with micronutrients, whole grains, and dietary fiber ingredients, meat flavor and comfort food innovations, and "clean" food product labels. In 2019, the European Union launched a program called Smart Protein to reuse large-scale, plant-based residues, such as pasta, bread, and yeast byproducts together with whole grains, as new high protein, flavorful substitutes for meat, seafood, and dairy products.
