Becoming vegan is all about avoiding foods derived from animals, including meat, eggs and milk.
But many people who switch to the diet say it not only benefits animals, but has a positive impact on their own health and happiness, too.
Here, six celebrities share their experiences.
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Since singer Miley Cyrus adopted a vegan lifestyle she's been vocal about her new choices on social media - including how she sources vegan "leather" for performing.
In one post she said: "So many good plants/fruits/veggies to eat you ain’t gotta eat dead animals!
"Everything that goes into my body is alive! To keep ME alive! Love this life!”
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Liam Hemsworth said he often receives questions like "how do you get protein?" since becoming vegan, but he's never felt better.
"Most of the people who ask you this are not healthy people. It always makes me so confused, because I’m like, 'what are you eating? Whatever you’re eating, it’s not right,'" he told Men's Health
"But there are no negatives to eating like this. I feel nothing but positive, mentally and physically. I love it.
"I feel like it also has a kind of a domino effect on the rest of my life."
Lea Michelle has become an ambassador for animal rights organisation Peta since becoming vegan.
In a video on the charity's website
, she says: "It's about being healthy and being smart and doing good for your body while at the same time being kind and smart to animals."
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Mike Tyson turned vegan in 2010 and has lost weight as a result.
"Becoming a vegan gave me another opportunity to live a healthy life," he said on “Oprah: Where Are They now?”
"I was so congested from all the drugs and bad cocaine, I could hardly breathe, [I had] high blood pressure, [was] almost dying [and had] arthritis. And once I became a vegan all that stuff diminished."
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Speaking after becoming vegan, Ellen DeGeneres said
there's "many reasons" to change your habits.
"I'm healthier for it, I'm happier for it," she said.
"I really truly believe that we take in energy and our thoughts are important... I can't imagine that if you're putting something inside your body that's filled with pain, anxiety and fear, that that isn't somehow going to be inside of you."
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Former president Bill Clinton adopted a vegan diet in 2010.
“I like the vegetables, the fruits, the beans, the stuff I eat now,” Clinton told a CNN reporter
“All 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.”
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In a blog on The Huffington Post
, actress Natalie Portman said her research into veganism has shown the lifestyle is better for people in manufacturing, as well as animals.
"The human cost of factory farming - both the compromised welfare of slaughterhouse workers and, even more, the environmental effects of the mass production of animals - is staggering," she said.
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Ariane Grande became vegan in 2013 and explained her decision to The Mirror, saying: "I love animals
more than I love most people, not kidding. But I am a firm believer in eating a full plant-based, whole food diet that can expand your life length and make you an all-around happier person."