Celebrities like Morrissey, Natalie Portman and even Arnold Schwarzenegger have been preaching the gospel of vegetarianism for some time.

Now, they have scientific evidence to back some of their claims.

A new study published in Proceedings of the National Academy of Sciences says that widespread adoption of vegetarian or vegan diets could millions of lives and trillions of dollars by 2050.

“Imbalanced diets, such as diets low in fruits and vegetables, and high in red and processed meat, are responsible for the greatest health burden globally and in most regions,” Marco Springmann, lead author of the study conducted at the Oxford Martin Programme on the Future of Food, told the U.K.’s Independent.

“At the same time the food system is also responsible for more than a quarter of all greenhouse gas emissions, and therefore a major driver of climate change.”

To conduct the study, researchers analyzed four different scenarios with humans consuming various levels of meat and dairy to observe how diet, health and the environment are linked from a global perspective.

In the scenario where humans consumed the least animal byproducts—a near universal adoption of a vegan diet— scientists found that about 8.1 million deaths could be averted by 2050. A vegetarian diet would save 7.3 million lives. Following the minimum global dietary guidelines, which includes eating more servings of fruit and vegetables and less animal proteins, could save 5.1million deaths.

Eating too much red meat has been linked to adverse health effects and the research found that cutting down on red meat alone accounted for half of the avoided deaths. The other half was due to a reduction in obesity rates linked to cutting calories from eating healthier foods.

In addition to noting widespread health improvement, the study also found that reducing meat consumption had a major impact on the environment.

A vegan or vegetarian diet could cut greenhouse gas emissions produced from raising livestock by 70 percent and 63 percent, respectively. Today, raising animals accounts for over 14 percent of global greenhouse emissions while those related to the food sector account for about half of the world’s emissions.

Economically, moving toward vegetarian or vegan diets could save up to $1 trillion annually in healthcare costs and lost working days due to illness worldwide.

The study also looked at the influence of dietary changes regionally. Researchers found that East Asian, Latin American and Western high-income countries would benefit the most from eating less red meat. In South Asia and Sub-Saharan Africa where meat consumption is typically low already, increasing fruit and vegetable intake will be beneficial. The geographic differences could help lawmakers create targeted policies.

But the researchers say individuals can also start simple making changes every day.

Says Springmann, “If society is serious about reducing greenhouse gas emissions, then we should be trying to make savings in every area of our day-to-day activities, including in our diet."