(CNN) -- Back in his college days, Matt Frazier says he never ran more than three miles at a time.
"I was kind of a recreational athlete at best," he said.
But that was before he adopted a plant-based diet.
The reformed "non-runner" went vegan in 2009 and became an endurance athlete who now competes in races up to 100 miles long.
The vegan performance hack
Elite athletes like Alex Morgan, Kyrie Irving and Venus Williams have turned to plant-based diets in hopes of gaining an edge. Research shows they may be onto something.
A study at George Washington University School of Medicine and Health Sciences found that plant-based diets can lower cardiovascular risk factors like plasma lipid concentrations, body weight and blood pressure.
"Plant-based diets give us the best access to a wide variety of nutrients and fiber and those things really help reduce fatigue, increase oxygen and blood flow to muscles," says Brittany Verras, an Emory University dietician working with athletes.
"It just really helps the overall picture of recovery," she adds. "The faster you can recover the better you can perform."
Journey to no meat
Frazier wasn't satisfied with his performance after he completed his first marathon. He'd hoped to qualify for the Boston Marathon.
"I missed the qualifying time by about 104 minutes," says Frazier.
"So, over five or six years, I really started learning as much as I could about running, learning how to avoid injuries and a big part of all that was my diet," he explains.
Not knowing if changing his diet would really make an impact, Frazier decided to ease his way into a plant-based diet and document his journey through his blog. Frazier first abstained from consuming land animals, then seafood and eventually eliminating dairy.
Verras says switching from processed to whole foods is one of the toughest transitions for those moving to a plant-based diet.
"Using processed meats or meat alternatives can be a great stepping stone for someone really struggling to figure out how a vegan diet works for their life," Verras explains. "The end goal needs to be whole, unprocessed foods."
"My diet evolved, and I started to eat more whole foods, less processed things," Verras says.
For Frazier, one of his biggest worries was losing meat as his source of protein.
"I, like everyone else, thought you have to get the protein from the meat," he said. "I found out that it was actually a misconception that you can't get protein from sources besides meat and dairy and animal products."
As Frazier interviewed people for his blog, he discovered many of the top athletes he spoke to were getting somewhere around 15% of their calories from protein.
"Honestly, if you just eat whole, plant-based foods you're going to end up somewhere near that amount," he said.
Verras says some people irrationally worry about protein when they consider a plant-based diet. She says there are far more protein sources beyond animals.
"People like to go protein crazy, but that's a mistake," the dietician points out. "If we eat too much protein at one time our body can't process it."
Verras says the key is focus on balance of nutrients.
"Carbohydrates provide the fuel and we store it for later use. We pull on that for endurance or really demanding periods like during sprinting, and then protein helps us build muscle and repair tissue," she said. "But as far as the vitamins and minerals, and this is true for all athletes, we need to be getting higher calcium, omega 3s and vitamin D."
Good sources of plant-based protein are soy, tofu, edamame, beans, lentils, legumes, nuts, and minimally processed nut butters, Verras says.
From marathon to ultramarathon
Frazier qualified for the Boston Marathon six months after changing his diet. After a few more marathons, he looked for another challenge and talked to a former high school classmate who ran a 100-mile ultramarathon.
The vegan runner became obsessed.
"I wanted to prove to myself that I could do this thing that seemed so impossible," he said.
With his diet completely plant based, Frazier says he didn't have to ween himself off any bad habits or foods. But he did have to find ways to replace the calories he lost from running upwards of 50 miles each week.
"I found myself just gravitating towards whole foods," he said. "I was spending probably 80% of my time and budget in a grocery store in the produce section and getting nuts and seeds and some whole grains."
Within a few years, Frazier was able to complete a 30, 50 and then a 100-mile ultramarathon. This all just seven years after running his first marathon.
"With the right training program, nutrition and some discipline you can actually do this."
Since meeting his fitness goals, Frazier is using his blog to help other vegan athletes connect and learn more about nutrition. He has more than 100,000 email subscribers. The growing interest has resulted in "No Meat Athlete" running groups across the country.
"They've been one of the most fulfilling things to me," says Frazier. "Just knowing I've shown people that you can do these things as a serious athlete."
"I'm a guy who, with the help of a plant-based diet, managed to do some pretty neat things athletically."
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