You Probably Didn't Know These 15 Celebrities Are Vegans

#1 Ellen DeGeneres

Similar to Natalie Portman, comedian and talk-show host Ellen DeGeneres switched to a vegan diet in 2008 after reading several books on animal rights and diets. "I do it because I love animals," DeGeneres told Katie Couric. "And I saw the reality and I just couldn't ignore it anymore." Degeneres' wife, Portia de Rossi, shares the same diet, and their 2008 wedding featured a vegan menu.

Perhaps one of the more vocal celebrities on this diet, she even has her own vegan blog, "Going Vegan With Ellen," and she and de Rossi are slated to open their own vegan restaurant, though its opening date is unknown.

#2 Al Gore

Al Gore is the latest celebrity to hop on the animal and dairy free diet. Forbes broke the news last weekend, saying he's a "newly turned vegan." It's unclear why the former vice president made the swap, but in doing so, he joins the 42nd president he once served in this dietary endeavor.

#3 Natalie Portman

Long-time vegetarian Natalie Portman went vegan in 2009 after reading Jonathan Safran Foer's Eating Animals. She even went on to blog about it on The Huffington Post. "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 wrote.

#4 Mike Tyson

Former heavyweight boxing champion Mike Tyson turned vegan in 2010, and has since loss 100 pounds. "Becoming a vegan gave me another opportunity to live a healthy life. 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," said Tyson earlier this year on "Oprah: Where Are They now?".

#5 Bill Clinton

After undergoing quadruple bypass surgery in 2004 and a later stent surgery, the 42nd president adopted a vegan diet in 2010. He's since lost 20 pounds, and has become an advocate for vegan and meatless diets.

#6 Carrie Underwood

Growing up on a farm, Carrie Underwood says she became a vegetarian at age 13 after witnessing animal killings first-hand. Slightly lactose intolerant, PETA's Sexiest Vegetarian Celebrity of 2005 and 2007 jumped to being a vegan in 2011.

It's not a completely strict meatless and dairy-free diet for this country star, though: She'll slip up for cultural or social reasons if need be. "I am a vegan but I consider myself to be a practical vegan," she told Entertainment Wise. "If I order something on a menu and it has a sprinkling of cheese on top I'm not going to send it back."

#7 Alicia Silverstone

This "Clueless" star went vegan more than 15 years ago at age 21, according to Health Magazine. Prior to the dietary switch, Silverstone told Oprah that she had puffy eyes, asthma, acne and insomnia and constipation.

The New York Times reports that this lifelong animal lover made the switch after watching documentaries on the food industry. Silverstone authored The Kind Diet, a book on vegan cuisine in 2009, and offers other diet pointers and green tips on her website, The Kind Life.

#8 Usher

This singer-songwriter-dancer went vegan in 2012, according to Mother Nature Network. His dad died of a heart attack in 2008, and RadarOnline reports that Usher is determined to take charge of his fate with this healthier diet.

Usher apparently tried to get his protégé, Justin Bieber, aboard the vegan train too, but he hasn't stuck with it.

#9 Joaquin Phoenix

This award-winning actor has likely had the longest bout at veganism of any celebrity. "I was 3 years old. To this day it is a vivid memory," Phoenix told the New York Daily News. "My family and I were on a boat, catching fish The animal went from a living, vibrant creature fighting for life to a violent death. I recognized it, as did my brothers and sisters."

#10 Carl Lewis

World-famous track runner and Olympic gold medalist Carl Lewis says he had the best race of his life at the 1991 World Championships, after he turned vegan to prepare for the race, Mother Nature Network reports. It was that year that he won ABC's Wide World of Sports Athlete of the Year and set a world record.

#11 Woody Harrelson

This Hunger Games star is hungry for all things dairy and animal free, and has been so for over 25 years, according to a previous Huffington Post article. "I was on a bus and some girl sees me blowing my nose," Harrelson is saying of his early years trying to make it as an actor in New York. "I had acne all over my face, which I'd had for years and years. And she's like: 'Hey, you're lactose intolerant. If you quit dairy, all these symptoms you got will be gone in three days.' I was like twenty-four. And I was like, No way. But three days later: gone," he told Esquire.

#12 Thom Yorke

The song "Meat is Murder" by The Smiths is said to have inspired Radiohead's founder and lead singer to adopt a vegan diet, according to Yahoo. He told GQ that meat consumption was tearing up his diet.

#13 Alanis Morissette

After reading Eat to Live by Dr. Joel Furhman and feeling unhealthy from weight gain and processed food, the singer-songwriter became vegan in 2009. On why she made the diet swap, she told OK magazine: "Longevity. I realized I want to live till I'm 120. There's a lifestyle that I am now happily creating that can, as best as is possible, prevent most forms of cancer and other diseases." She also says in the interview that she lost 20 pounds within months of becoming vegan and feels more energetic. Morissette does note, however, that she is 80 percent vegan. "The other 20% is following what my body needs," according to the Guardian.

#14 Russell Brand

After watching "Forks Over Knives," a documentary on rejecting processed food to control common diseases, Russell Brand converted from longtime vegetarian to vegan in 2011, according to Mother Nature Network. Once he made the switch, PETA's 2011 Sexiest Vegetarian Celebrity tweeted, "I'm now vegan, goodbye eggs, hello Ellen."

#15 Morrissey

This long-time vegetarian and vegan made headlines this year for his outspoken views on veganism and animal rights. Most recently, he called the White House's annual turkey pardon "Thankskilling" and wrote on a fan website, "Please ignore the abysmal example set by President Obama who, in the name of Thanksgiving, supports torture as 45 million birds are horrifically abused; dragged through electrified stun baths, and then have their throats slit. And President Obama laughs. Haha, so funny!" according to Rolling Stone.