A plant-based diet is a way of eating that includes mostly or all plant foods. It includes many different types of eating plans that have little animal food and lots of plant foods that are high in fiber, such as vegetables, fruits, whole grains, legumes, nuts, seeds, herbs, and spices. Some plant-based diets are vegan or vegetarian, but others are not. This type of diet is defined by eating many plant foods and few animal foods.
Terminology
The term "plant-based diet" is credited to T. Colin Campbell, a scientist who studies nutrition at Cornell University. In 1980, he shared his research about plant-based diets with the US National Institutes of Health. His work was based on The China Project, a study lasting 10 years that examined eating habits in rural China. This research showed that diets with less animal protein and fat, and more plant foods, could lower the risk of certain diseases. In 2005, Campbell and his son wrote a book called The China Study, which became popular and highlighted the health benefits of eating more plant foods. The book also explained how eating meat can harm the environment.
Some writers explain that "plant-based" and "plant-only" diets are different. A plant-based diet includes foods from plants that are not highly processed.
A review of medical research found that in half of the studies, the term "plant-based diet" was used the same as "vegan," meaning no animal products were included. In 30% of the studies, dairy products were allowed, and in 20%, meat was included.
In 2021, the World Health Organization (WHO) said that "plant-based diets include many types of eating patterns that focus on foods from plants and have less or no animal products. Vegetarian diets are a type of plant-based diet and may avoid some or all animal foods." The WHO lists several types of plant-based diets, including flexitarian, lacto-vegetarian, lacto-ovo vegetarian, ovo-vegetarian, pescatarian, and vegan.
A 2023 review paper described a plant-based diet as "a way of eating where foods from animals are completely or mostly avoided."
In 2024, the International Organization for Standardization created a draft called ISO 8700, which provides definitions and rules for labeling and claims about plant-based foods and ingredients.
Motivation and prevalence
As of the early 21st century, about 4 billion people mainly eat plant-based foods. Some choose this diet, while others do so because of limited access to crops, fresh water, and energy. Common reasons for eating plant-based foods include wanting to be healthy, enjoying the taste, caring about animal welfare, being concerned about the environment, and wanting to lose weight. In the U.S.A., people make personal choices about their diet to help with climate change. Twenty-six percent of those who eat plant-based foods are "alarmed" about global warming, as defined by the Yale Program on Climate Change Communication: these people believe global warming is happening, caused by humans, and an urgent threat. Twenty-seven percent eat plant-based foods because they are "concerned" about global warming—they believe it is real and serious, caused by humans, but think its effects will happen far in the future and are less urgent. About one-third of greenhouse gas emissions are connected to making and moving food. The largest source of emissions from food comes from agriculture and land use. More than two-thirds of farmland is used to raise animals for food, while only 8% is used to grow food directly for humans.
Health guidelines and research
Plant-based diets are being studied for their role in preventing and managing long-term health conditions. The British Dietetic Association said that a plant-based diet can support healthy living at every age and life stage, but it should be carefully planned. The Government of Canada and the Heart and Stroke Foundation of Canada released 2024 guidelines on using plant-based protein in meals, including ideas for replacing meat with plant foods.
Not all plant-based foods are equally healthy. Diets rich in whole grains, unsaturated fats, fruits, vegetables, and n-3 fatty acids are considered healthier.
As more processed plant-based foods become available, there is concern that diets including these may be less healthy.
People who follow lacto-ovo vegetarian or vegan diets often have better overall diet quality than nonvegetarians. This is because they tend to follow health guidelines more closely, such as eating more fruits, whole grains, seafood, and plant protein, and less sodium. The higher diet quality in vegetarians and vegans may explain some of the positive health outcomes compared with nonvegetarians.
Plant-based foods are not naturally rich in vitamin B12. A lack of B12 can lead to health issues. Those on a fully plant-based diet should get B12 from supplements or fortified foods like plant milks, yogurts, nutritional yeast, or cereals.
Even those with a plant-based diet that includes some animal products may not get enough B12 without supplements or fortified foods.
Studies show that vegetarian diets have lower energy intake and that vegetarians, on average, have a lower body mass index than non-vegetarians.
Two reviews found that vegetarian diets over 18 weeks reduced body weight by 2–3 kg, and vegan diets over 12 weeks reduced weight by 4 kg.
In obese people, a 2022 review found that plant-based diets improved weight control, LDL and total cholesterol, blood pressure, insulin resistance, and fasting glucose.
Some reviews suggest that plant-based diets with fruits, vegetables, whole grains, legumes, and nuts lower diabetes risk. Research is ongoing to see how vegetarian and vegan diets affect type 2 diabetes, with early results showing weight loss and better metabolic markers.
Focusing on whole foods in plant-based diets improved diabetes markers, reduced obesity, and improved well-being in diabetic individuals.
The American College of Lifestyle Medicine says that a diet rich in whole, plant-based foods with little meat can help many adults with type 2 diabetes achieve remission. More studies are needed to test long-term plant-based diets as a treatment.
Plant-based diets are linked to lower risks of colorectal and prostate cancer. Vegetarian diets reduce total cancer risk by 8%, and vegan diets by 15%, but not cancer mortality.
Early studies suggest that plant-based diets may improve gut health.
A 2022 review found vegetarian diets lower cardiovascular disease risk by 15% and coronary artery disease by 21%, but no effect on stroke. Vegan diets only reduced coronary artery disease risk.
Plant-based diets may lower cardiovascular risks, including blood pressure and lipid levels. Vegan diets without calorie restrictions can lower blood pressure by about 4 mmHg, similar to medical recommendations.
The effect of plant-based diets on bone health is unclear. Some studies suggest lower bone density, which increases fracture risk.
Plant-based diets may reduce inflammation, as shown by lower C-reactive protein levels, especially in obese individuals.
A 2020 review found that diets rich in vegetables, fruits, legumes, nuts, whole grains, and unsaturated oils, with less processed meat and refined carbs, lower all-cause mortality risk.
A 2023 meta-analysis showed plant-based diets improve aerobic performance moderately but have no effect on strength performance.
Sustainability
Scientific agreement exists that plant-based diets produce fewer greenhouse gases, use less land, and protect biodiversity better than diets high in animal products. Diets that reduce health risks from poor eating habits also help the environment stay healthy.
Many crops worldwide are used to feed animals instead of people. Eating fewer animal products can reduce climate change and protect wildlife. Beef, lamb, and cheese have very high carbon footprints. Although soy farming is a major cause of deforestation in the Amazon, most soy is used to feed livestock, not humans. Choosing plant-based foods can reduce the number of animals raised and killed for food in factory farms.
A 2019 study compared six diets and found that plant-based diets, such as vegan, vegetarian, and pescetarian, had lower carbon footprints than diets higher in animal products. Diets like paleolithic and ketogenic had higher carbon emissions because they rely more on animal-sourced foods.
A 2020 study showed that changing to plant-based diets worldwide could reduce climate change effects. These diets use less land and produce less CO2 compared to meat and dairy. This change could balance out the CO2 emissions from burning fossil fuels over 9 to 16 years. Researchers also created a map showing where these changes could be most effective.
Social influence, such as when people see others eating plant-based foods, can encourage more people to adopt similar habits. A 2020 study found that meat-eaters are more likely to choose vegetarian meals when vegetarians are nearby and when meat and meat-free options are available. As more people adopt plant-based eating, a community may reach a tipping point, where a majority of people change their habits. A 2018 study found that only 25% of a population could influence the majority to change.
A 2021 report by Chatham House, supported by the United Nations Environment Programme, stated that shifting to plant-based diets is needed to protect biodiversity and reduce human harm to the environment. Livestock farming uses about 80% of global farmland for raising cattle, sheep, and other animals. Switching to plant-based diets could free up land to restore ecosystems and support wildlife.
A 2022 study found that if high-income countries adopted plant-based diets, large areas currently used for animal farming could return to natural states. This could remove up to 100 billion tons of CO2 from the atmosphere by the end of the century. About 35% of all habitable land globally is used for raising animals for food.
A 2023 study showed that a vegan diet reduces environmental harm from food production by 75%, lowers water pollution by 54%, and reduces land use by 75%. Another 2023 study found that replacing half of global beef, chicken, dairy, and pork consumption with plant-based alternatives could reduce farmland use by nearly one-third, stop deforestation, restore biodiversity, and cut agricultural greenhouse gas emissions by 31% by 2050. However, the report also noted that growing populations and increased wealth may raise demand for animal products, which could harm the environment.
Politics
To meet climate goals, improve public health, and care for animals, it is important to cut down on meat and eat more plant-based foods. Studies have shown ways to encourage people to make this change.
Some health organizations, like the Swedish Food Agency, recommend eating more plant-based foods because they are better for the environment. A group of researchers from The Lancet also suggest a diet that helps both the planet and people's health. Greta Thunberg, a climate activist, encouraged more plant-based food production and eating worldwide. A 2022 report by the Stockholm Environment Institute and the Council On Energy, Environment and Water suggested protecting animals and eating more plant-based foods to help solve environmental and social problems. In 2023, Denmark and South Korea started plant-based action plans. Plant-based protein is becoming more popular as a healthy and eco-friendly option.