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The Best Diet for Athletic Performance

You run, you jump, you walk. What do you eat? This episode features audio from Why All Athletes Should Eat Plant-Based Diets, Do Alkaline Diets Help Athletic Performance?, and The Gladiator Diet and the First Studies on Vegetarian Athletes. Visit the video pages for all sources and doctor’s notes related to this podcast.


Did you know that plant-based diets are gaining in popularity among athletes? In our first story, we discover why folks are drawn to plant-based diets for athletic performance and recovery.

Consumer interest in eating plant-based has surged over the last few years, and athletes are no exception. While in the past, meat was seen as an irreplaceable performance-enhancing food, today, the trend is developing in the opposite direction, thanks in part to documentaries like The Game Changers, for which I was honored to play a role as scientific advisor.

Several high-profile athletes, from heavyweight champion boxers to tennis players, have tried fueling with plants. Athletes have increasingly been adopting plant-based diets––not only for the related health benefits, but for perceived improvements in endurance performance. In fact, even by 2016, there were reports of up to a third of ultra-endurance runners, for example, shunning meat.

Increasing plant-based foods may boost vasodilatory—meaning artery-dilating, antioxidant, and anti-inflammatory properties of the diet–which can lead to improved blood flow, reduced oxidative stress and inflammation, and thus, theoretically enhance endurance performance, reduce muscle damage, and speed recovery. Exercise itself can release free radicals that can also lead to muscle fatigue, reduced athletic performance, and impaired recovery, but the antioxidants concentrated in plant foods can help extinguish them.

Shifting to a dietary pattern with more plants and less animal-sourced food has been shown to attenuate inflammation. A systematic review and meta-analysis comparing common biomarkers of inflammation found that meat-free diets appeared to be favorable in all cases. And not just inflammation, but immune status. Having a strong immune system is important for athletes, especially endurance athletes, as they are often immunocompromised, which increases risk of upper respiratory tract infection. After a marathon, there can be about six-fold higher odds of coming down with an infection, and after an ultramarathon as many as 68 percent fall ill within the ensuing two weeks. But hey, a better immune system could translate into less illness––which means more time training for the plant-based athlete, though this has yet to be studied directly.

We also know there’s an ergogenic, meaning performance-enhancing, effect to nitrates, and nitrates in the bloodstream of vegetarians is about 20 percent higher, and in vegans 40 percent higher, likely due to their eating more nitrate-rich vegetables, such as beets, spinach, and other greens.

And then there are all the health benefits that could boost performance in the long term. It is well-documented that plant-based diets reduce the risk of chronic disease, such as cardiovascular disease, diabetes, metabolic syndrome, and cancer, and all-cause mortality––meaning living a significantly longer life.

But do high-performing athletes really need cardiovascular protection? Surprisingly, endurance athletes may have more advanced atherosclerosis and more heart muscle damage, compared with sedentary individuals. Male athletes had a higher prevalence of atherosclerotic plaques in their coronary arteries compared with sedentary males. A higher prevalence of high coronary artery calcium, a greater number of atherosclerotic plaques, including multivessel plaques, and a greater proportion squeezing off blood flow more than 50 percent.

Marathon runners, found to have increased total atherosclerotic plaque volume—calcified plaques, non-calcified plaques. Paradoxically, worse atherosclerosis in their coronary arteries, which may then translate into more damage to the heart muscle itself—three times more than matched sedentary individuals. They are running the risk of coronary events. It’s the kind of heart damage you see after heart attacks. But wait, why? Why do studies show that well-trained athletes are at significant risk for atherosclerosis and heart damage? It may not be that they’re overstressing their heart with movement, but rather overstressing their heart with saturated fat and cholesterol. Endurance athletes can eat 5, 6, 7,000 calories a day. So, if you’re eating twice the Big Macs, no wonder their poor hearts are getting hammered.

That’s where plant-based diets come in––the only diet shown to be able to reverse the progression of heart disease in the majority of patients. Yeah, such diets may also contribute to improved performance and accelerated recovery, but most importantly, will allow you to recover and maintain your long-term health. Athletic performance suffers, when you’re dead.

In our next story, we look at the benefits of reducing acid-forming foods and boosting alkaline-forming foods.

Theoretically, bathing your muscles in an alkaline environment should enable faster acid removal from muscle cells, delaying the muscle fatigue that’s due to the build-up of lactic acid in the muscle. Given these buffering effects, no wonder sodium bicarbonate—in other words, baking soda—has been found to have such significant ergogenic or performance-enhancing effects on muscular endurance. The problem with loading with baking soda is that it frequently causes severe gastrointestinal distress, and at standard doses you could easily take in twice the recommended upper daily limit of sodium in just that one load. Therefore, what about a low-acid diet, which focuses on high intakes of fruits and vegetables? That may be an attractive alternative to bicarbonate loading for improving anaerobic exercise performance, meaning short-burst activity like sprinting.

Today’s diets are acid-forming, meaning higher in animal foods with fewer vegetables and fruits; whereas, in general, the alkaline-promoting diet is centered around whole plant foods, with few processed foods and less meat, dairy, and eggs, which are accepted as acid-forming foods.

Although alkalinizing chemicals such as sodium bicarbonate have been shown to consistently improve performance, alkalinizing diets do not demonstrate the same effect. A review of ten studies that investigated the effect of high versus low dietary acid loads on athletic performance did not find consistently improved exercise performance at maximal or submaximal exercise intensities. However, maybe they just didn’t go alkaline enough.

For example, in this study, they had people eat more fruits and vegetables, and less meat, cheese, cereals, and eggs, but saw no differences in any performance-related parameters. But a sufficiently alkaline diet is characterized by the production of alkaline urine––a pH of pee at least 7 or higher. If you look at what the participants achieved, most failed to meet the benchmark; so, their diet may just not have been alkaline-forming enough.

In this study showing enhanced 400-meter sprint performance, they were able to swap out enough meat, eggs, cheese, and cereal products, and swap in enough fruits and vegetables that they were just barely able to make 7. And they did get a little performance boost, suggesting that it is possible to improve sprint performance by consuming alkalizing natural foods and beverages, without the ingestion of baking soda. Thus, an alkalizing diet may be an easy and natural way to enhance performance; however, the performance enhancement was only about 2 percent—just a few seconds. But check out this study.

The same general strategy: more fruits and vegetables, and less of the acid-promoting foods, such as meats, cheeses, and refined grains; but they weren’t messing around. Six to eight cups of vegetables, plus more than four servings of fruit a day, got their urine up over 7, and they had a 21 percent performance enhancement. That’s extraordinary.

Now, this doesn’t necessarily mean it has anything to do with the pH. I mean, they ate more vegetables, which contain dietary nitrates, which alone acutely improve exercise performance. It’s possible that nitrates might have enhanced exercise performance during the low-acid trial. However, that would entail extracting more energy from every breath, and they didn’t find that. But any time you make huge changes in people’s diets, it’s hard to pinpoint exactly what made the critical difference. But these extra benefits are a feature, not a bug. Because a more alkaline-forming diet is rich in fruits and vegetables, and deplete of many unhealthy foods, a low-acid diet could not only provide exercise performance benefits, but might also reduce chronic disease risk.

Any performance benefits in non-athletes? The effect of an alkaline diet on body composition and aerobic exercise performance of sedentary women. A randomized controlled trial, swapping in vegetable protein sources like legumes for animal protein sources and…a greater decrease in weight, body fat mass, lactic acid accumulation, and perceived exertion levels, all the while exhibiting a boost in exercise performance duration and VO2Max levels, which is a measure of fitness. Again, pH could just be one of many explanations why eating healthier could make you perform better, but either way, we should recommend athletes of all ages focus on consuming ample amounts of fruits and vegetables, if only to maintain long-term health.

Finally, today, we go back in time – way back – to compare the diets of the Roman gladiator “barley men” to the modern Spartans of today.

Recently, the remains of dozens of Roman gladiators were discovered in a mass grave. The clue to their identities were the rather distinct types of mortal injuries they found, like being speared in the head with a trident. Using just their skeletons, they were able to reconstruct the death blows, show just how buff they really were, and even try to reconstruct their “diet of barley and beans.” You can look at carbon isotopes and see what kinds of plants they ate; “nitrogen isotopes…reflect [any] intake of animal protein.” You can also look at the sulphur in their bones and the amount of strontium, leading commentators to submit that the best athletes in ancient Rome ate largely plant-based diets.

Then, there were the legionnaires, the Roman army troopers, famed for their abilities, also eating a similar kind of diet, suggesting “The best fighters in the ancient world were essentially vegetarian.” So, if the so-called “perfect fighting machine[s],” the great sports heroes of the day, were eating mostly grains and beans, should that tell us anything about sports nutrition and the preferred diets of elite athletes? Well, most of the Greeks and Romans were “basically vegetarian” and centering their diets around grains, fruit, vegetables and beans; so, maybe the gladiators’ diets weren’t that remarkable. Plato, for example, pushed plants, preferring plant foods for their health and efficiency.

So yes, “the Roman gladiators were known as [the] ‘barley men.’” But is that because barley gives you “strength and stamina”? Or was that just the basic food that people ate at the time, not necessarily for performance, but because it was just so cheap?

Well, if you look at “the modern Spartans,” the Tarahumara Indians, the ones that run races where they kick a ball for oh, 75 miles just for the fun of it, running all day, all night, and all day, maybe 150 miles if they’re feeling in the mood. What do you get if you win? “[A] special popularity with the [ladies] (although how much of a reward that would actually prove to be for a man who had been running for two days [straight] is questionable,” though maybe their endurance extends to other dimensions). “Probably not since the days of the ancient Spartans has a people achieved such a high state of [extreme] physical conditioning.” And what did they eat? The same kind of 75 to 80 percent starch diet based on “beans, corn, and squash.” And, they had the cholesterol levels to prove it, total cholesterol levels down at an essentially heart attack-proof 136. And it’s not some special genetics they have—you feed them enough egg yolks, and their cholesterol creeps right up.

Modern day Olympian runners eat the same stuff. What are they eating over there in Kenya? A 99 percent vegetarian diet centered mostly around various starches. But as in all these cases, is their remarkable physical prowess because of their diets, or in spite of their diets? Or have nothing to do with their diets? You don’t know…until you put it to the test.

“In spite of well-documented health benefits of [more plant-based] diets, less is known regarding the effects of these diets on athletic performance.” So, they “compared elite vegetarian and omnivore…endurance athletes for [aerobic fitness] and strength.” So, comparing oxygen utilization on the treadmill, and quad strength with leg extensions. And the vegetarians beat out their omnivore counterparts for “cardiorespiratory fitness,” but their strength didn’t differ. Suggesting, in the very least, that vegetarian diets “do not compromise athletic performance.”

But this was a cross-sectional study. Maybe the veg athletes were just fitter because they trained harder? Like in the National Runners’ Health Study looking at thousands of runners: vegetarian runners were recorded running significantly more on a weekly basis; so, maybe that explains their superior fitness. Though, maybe their superior fitness explains their greater distances.

Other cross-sectional studies have found no differences in physical fitness between vegetarian and non-vegetarian athletes, or even worse performance, as in this study of vegetarian athletes in India. Of course, there could be socioeconomic or other confounding factors. That’s why we need interventional studies to put different diets to the test and then compare physical performance, which we’ll explore next.

In 1896, the aptly named James Parsley evidently led a successful vegetarian cycling club to victory. Their competitors evidently having to “eat crow with their beef.” Evidently some Belgian put it to the test in 1904, with those eating more plant-based supposedly lifting some weight like 80 percent more times, but I couldn’t find the primary source in English. This I could find, though: a famous series of experiments at Yale, published more than a century ago, on the influence of flesh-eating on endurance.

Forty-nine people were compared: regular athletes (mostly Yale students), vegetarian athletes, and then just sedentary vegetarians. “The experiment furnished a severe test of the claims of those flesh-abstainers.” Much to the researchers’ surprise, the results seemed to vindicate the vegetarians, suggesting that not eating meat leads to far greater endurance compared to those accustomed to the ordinary American diet.

Check it out: the first endurance test was how many minutes straight you could hold out your arms horizontally: flesh-eaters versus flesh abstainers. The regular Yale athletes were able to keep their hands out for about 10 minutes on average. It’s harder than it sounds; give it a try. OK, but those eating vegetarian did like five times better. The meat-eater maximum, was only half that of the vegetarian average. Only two meat eaters even hit 15 minutes, whereas more than two-thirds of the meat-avoiders did. None of the regular diet folks hit a half hour; whereas, nearly half of the healthier eaters did, including nine that exceeded an hour, four that exceeded two hours and one guy going for more than three hours.

How many deep knee bends can you do? One athlete could do more than 1,000, averaging 383, but they got creamed even by the sedentary plant-eaters. That’s the crazy thing—even the sedentary abstainers surpassed the exercising flesh-eaters. The sedentary abstainers were in most cases physicians who sat on their butts all day. I want a doctor that that can do a thousand deep knee bends!

And then in terms of recovery, all those deep knee bends left everyone sore but much more so among those eating meat. Among the vegetarians, of two that did like 2,000 knee bends one went straight off to the track to run, and another went on to their nursing duties. On the other hand, among the meat-eaters: one guy reached 254, went down once more and couldn’t get back up, had to be carried away and was incapacitated for days, another impaired for weeks after fainting.

It may be inferred, without reasonable doubt, concluded the once skeptical Yale researcher, that the meat-eating group of athletes was very far inferior in endurance to the vegetarians, even the sedentary ones. What could account for this remarkable difference? Some claimed that flesh foods contained some kind of “fatigue poisons,” but one German researcher who detailed his own experiments with athletes offered a more prosaic answer. In his book on what looks like physiological studies of uber-driving vegetarians—I told you I only know English—he conjectured that the apparent vegetarian superiority was just due to their tremendous determination to prove their point and spread their propaganda; so, they just make a greater effort in any contest than do their meat-eating rivals. The Yale researchers were worried about this; and so, special pains were taken to stimulate the flesh-eaters to the utmost, appealing to their college pride. Don’t let those lousy vegetarians beat the “Yale spirit.”

The experiments made it into The New York Times. Yale’s flesh-eating athletes—sounds like a zombie movie—beaten in severe endurance tests. “Yale professor believes that he has shown definitely the inferiority in strength and endurance tests of meat eaters compared to those who do not eat meat.” Some of Yale’s most successful athletes took part in the strength tests, and Professor Fisher declares they were obliged to admit their inferiority. How has the truth of this result been so long obscured? One reason, Professor Fisher suggested, is that vegetarians are their own worst enemy. In their fanaticism, they jump from the premise that meat eating is wrong—often based on scripture or some kind of dogma—and jump from that to meat-eating is unhealthy. That’s not how science works, and such logical leaps get them dismissed as zealots, and prevent any genuine scientific investigation. Lots of science, even back then, was pointing a distinct trend toward more plant-based eating, and yet the word vegetarian—even 110 years ago—had such a bad, preachy rap that many were loath to concede the science in its favor. The proper scientific attitude is to study the question of meat-eating in precisely the same manner as one would study the question of anything else.

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