There's a myth that vegans don't get enough nutrients, but then there's athletes like ultramarathoner Brendan Brazier, whose book "Thrive" explains how a plant-based diet helps improve performance and recovery when training, and superstar sprinter Carl Lewis, who credits a vegan diet for helping him win all those Olympic gold medals. Brendan and Carl are not the only ones to tout a plant-based lifestyle -- check out how it has helped these five vegan and vegetarian female athletes stay fast and fit.
• Debbie Lawrence: Racewalker Debbie Lawrence has been a vegetarian for many years, including when she competed in three Olympics and various world championships. She's also held the world record for the racewalker 5K and is a Pan American Games silver medalist.
• Fiona Oakes: Cyclist Fiona Oakes has been a vegan for over 20 years, in which time she's competed as a track cyclist in the 1992 Olympics. She's won several titles for the UK as a cyclist, and when she's not on her bike, she's running. With 24 marathons under her belt, Fiona's currently taking part in the six-day, 151-mile Marathon des Sables endurance race.
• Ruth Heidrich: Ruth Heidrich knows about running. The author, athlete, and raw food advocate, who's been a vegan for over 30 years, holds gold medals in races ranging from 5Ks to ultramarathons and has competed in several Ironman triathlons.
• Martina Navratilova: Before Martina Navratilova competed on "Dancing With the Stars", she was winning titles in the tennis world. The tennis champ credits a plant-based diet for allowing her to compete -- and win -- well into her 40s. "It made me mentally sharper and made it possible for me to endure the physical conditioning that is required to compete at that level," Martina has said.
• Venus Williams: After a diagnosis of the rare autoimmune disease Sjögren's Syndrome (which caused her to drop out of last year's Australian Open), Venus drastically changed her diet. Now the tennis star, who competed in a match last month, is sticking to a raw vegan diet in the hopes that it will help reduce the symptoms of her disease.