Photo

With the publication this month of “Eat and Run: My Unlikely Journey to Ultramarathon Greatness,” by the vegan distance runner Scott Jurek, vegan diets have become a wildly popular topic on running-related Web sites. But is going totally meatless and, as in Mr. Jurek’s case, dairy-free advisable for other serious athletes, or for the rest of us who just want to be healthy and fit?

Phys Ed Gretchen Reynolds on the science of fitness.

To find out, I talked with three experts about why, and whether, those of us who are active should consider giving up meat or more. None of the experts are themselves vegan, though two are vegetarian: David C. Nieman, a professor of health and exercise science at Appalachian State University, who’s run 58 marathons or ultramarathons and has studied runners at extreme events; and D. Enette Larson-Meyer, an associate professor of human nutrition at the University of Wyoming, as well as a longtime competitive athlete and author of “Vegetarian Sports Nutrition.” A third expert, Nancy Clark, who describes herself as “two-thirds vegetarian” — she doesn’t have meat at breakfast or lunch, but does at dinner — is a sports nutrition expert in Massachusetts and the author of “Nancy Clark’s Food Guide for Marathoners.”

Q.

Will a vegan diet make someone a better athlete?

A.

Nancy Clark: I was just at the American College of Sports Medicine Annual meeting in San Francisco, and there was a presentation about vegetarian athletes that basically concluded that there’s not enough research to know how vegetarian — let alone vegan — diets affect athletes. But anecdotally, people do fine. It’s possible that some vegan athletes are low on creatine, a nutrient that you get only from meat and that can help during short bouts of intense exercise, like sprinting, though supplementation isn’t necessary. My feeling is that hard training trumps everything. Diet, if it’s healthy, isn’t going to make that much difference.

Q.

Is it hard for someone who’s training vigorously to get enough protein on a vegan diet?

A.

David Nieman: The foods that vegans like Scott Jurek avoid, like dairy products and eggs, are the easy ways to get protein in a plant-based diet, obviously. But you still have grains, nuts, soy. Eat enough of that and you’ll be fine. The one issue is vitamin B12, which is found only in meat; B12 is important for endurance athletes, since it affects red blood cell production. But many cereals and soy milks are fortified with B12 now, or you can take supplements.

Nancy Clark: You do have to be diligent about protein intake if you’re vegan. I have clients, especially women, who say, ‘Oh, I put a few chickpeas in my salad.’ But that’s not going to do it. Women need about 60 to 90 grams of protein a day, and athletes are on the high end of that. That means you have to eat cupfuls of chickpeas. And you can’t eat a quarter of that cake of tofu. You need to eat the whole thing. It’s not that there aren’t good sources of vegan protein. But it’s not as bioavailable as meat. So you need to have more.

Q.

Is it true that you can combine plant proteins throughout the day to create complete proteins? You don’t have to eat them all at the same meal?

A.

D. Enette Larson-Meyer: Years ago, studies in rats showed that if they were fed only one source of protein, like corn, all day, they did not get sufficient amounts of essential amino acids. From that, the idea grew that you had to combine proteins at the same meal. But since then, other studies have found that if you get multiple sources of protein throughout the day, that’s fine. Have rice at breakfast and beans at lunch or dinner.

Q.

Is it hard for someone who’s training vigorously to get enough calories on a vegan diet?

A.

Nancy Clark: It’s not hard at all. My favorite weight gain or weight maintenance advice is to drink juice. Grape juice, pomegranate juice, tart cherry juice. They have plenty of calories, and if you pick the right juice, especially pomegranate or tart cherry juice, it looks as if they can help with recovery. Tart cherry juice was a very popular topic at the recent American College of Sports Medicine meeting. It’s a potent beverage, in terms of speeding recovery. And it’s vegan.

Q.

Will vegan or even vegetarian diets help you to lose weight?

A.

David Nieman: Short answer: No. Vegetarians tend to weigh 6 to 10 pounds less than meat eaters. But that’s probably due to self-selection bias. Many vegetarians are more health conscious to start with. You can overeat on a plant-based diet. There are obese vegetarians. Junk food can be vegetarian. You still have to make healthy food choices, whatever your diet.

Q.

Because of Scott Jurek’s book and others, there’s some sense out there that athletes should become vegans. Do you agree?

A.

David Nieman: I know Scott. He’s been a subject in some of our studies at the Western States 100. He’s a great guy — opinionated, sure, but he’s been very successful as a racer, so he can have opinions. But runners always think they have inside information on nutrition. They don’t. It’s my duty as a scientist to separate out the hype from what’s been validated.

What we know is that when it comes to endurance performance, it’s all about the fuel, primarily carbohydrates, and you can get sufficient carbohydrates whether you’re a vegetarian or a meat eater — unless you follow a really goofy diet, which some people do. It’s possible to eat a lousy vegetarian diet, just as you as can eat a lousy meat-based diet.

Q.

So is there any compelling reason for those of us who are active but not necessarily running ultramarathons to decide to become vegan?

A.

D. Enette Larson-Meyer: In general, vegetarians are healthier, with less risk for heart disease and obesity, although there are obese vegetarians. Many people tell me after they start a vegetarian diet that they feel better, but then again, many of them — and I believe this was the case with Scott Jurek — were eating a pretty poor diet before, so of course they feel better. They could have switched to a healthier meat-based diet and they would probably have felt better.

I like to tell people that if we got most Americans to eat one less serving of meat every day, there would be far greater impact from that, in terms of improving overall public health and the health of the planet, than convincing a tiny group of endurance athletes to go full vegan.

Gretchen Reynolds is the author of “The First 20 Minutes: Surprising Science Reveals How We Can Exercise Better, Train Smarter, Live Longer” (Hudson Street Press, 2012).

We hope you’ll “Like” the new Well on Facebook, where you’ll find news and conversations about fitness, food and family health.