Have you ever wondered if there’s a natural way to lower your high blood pressure, guard against Alzheimer's, lose weight, and feel better? Well as it turns out there is. Michael Greger, M.D. FACLM, founder of NutritionFacts.org, and author of the instant New York Times bestseller “How Not to Die” celebrates evidence-based nutrition to add years to our life and life to our years.

The Best Diet for Optimal Athletic Performance

Today on the Nutrition Facts podcast, we explore a variety of nutrient-rich foods that can enhance our workout.

This episode features audio from Foods to Improve Athletic Performance and Recovery, Fennel Seeds to Improve Athletic Performance, and Whole Beets vs. Juice for Improving Athletic Performance. Visit the video pages for all sources and doctor’s notes related to this podcast.


Today we’re going to look at the research on the best diet for optimal athletic performance. Starting with the effects of spinach and berries on oxidative stress, inflammation, and muscle soreness in athletes

Higher fruit and vegetable consumption was found to be “positively associated with muscle power” in adolescents, but that’s not who really needs it. What about the “consumption of fruit and vegetables and risk of frailty” in the elderly? Higher “[fruit and vegetable] consumption was associated with…lower…frailty” as well, “in a dose-response manner”—meaning more fruit, less frailty, and more vegetables, too. But these were all observational studies, which can’t alone prove cause and effect.

What happens when you put foods to the test? Well, “no positive influence…ingesting chia-seed oil on human running performance,” but there was an effect found for “spinach supplementation on exercise-induced oxidative stress.” And, by spinach supplementation, they meant they just gave some guys some fresh raw spinach leaves—one gram per kilo. So, like a quarter of a bunch a day for two weeks, and then they had them run a half-marathon. And, they found that “chronic daily oral supplementation of spinach”—uh, meaning like eating a salad—”had alleviating effects on known markers of oxidative stress and muscle damage.”

Here’s what happens when you run a half-marathon without spinach: a big spike in oxidative stress, blood malondealdehyde levels, that stay up hours or even days later. In the spinach group, the before-and-after two weeks of spinach doesn’t seem to make much of a difference. But, put the body under pressure, and then you can really see the difference. Your body is better able to deal with the stress.

And, if you look at the resulting muscle damage, as measured by creatine kinase leakage from your muscles (an enzyme that should be in your muscles, not leaking out into your blood), you start out at about 100, and go up to 200 after the half-marathon. Right after, two hours later. But, it’s the next day where you really feel it—that delayed-onset muscle soreness, with CK levels reaching 600 before coming back down. That’s without spinach, though. On spinach, you get a similar immediate post-race bump, but it’s that next day where spinach really shines. You don’t get the same next-day spike. So, for a competitive athlete, that quicker recovery may get you back training harder sooner. They attribute this to “the anti-inflammatory effects of spinach.”

Same with black currant juice. After some hardcore weightlifting, muscle damage indicators go up and stay up, whereas the same lifting, drinking berries, and it goes up, but comes right back down. But, these were just measures of a biomarker of muscle soreness. What about actual soreness?

If you look at the effects of tart cherry juice “on recovery following prolonged, intermittent” sprints in soccer players, you see the same kind of reduction in biomarkers of inflammation—but, more importantly, less resulting muscle soreness. Here’s the soreness reported in the days afterwards in the placebo group. Only about half in the cherry group. Then, they measured maximum voluntary isometric contractions of the leg muscles, which understandably took a hit in the days after the intense workout, but not in the cherry group.

They conclude “that participants who supplemented with [a tart cherry concentrate] were able to maintain greater functional performance.” But, that was testing like how high can you vertically jump. They didn’t actually see if they played soccer any better. But, this study on purple grape juice actually showed “an ergogenic effect in recreational runners by promoting increased time-to-exhaustion,” where you ramp people up on a treadmill and see how long they can go before collapsing. After a month of drinking a grape Kool-Aid type placebo control drink, no real change in performance, but a whopping 15% improvement in the real grape group, who hung on for another 12 minutes.

These studies used juice, so they could make a matched placebo control drink. But, you can buy Concord grapes fresh, or tart cherries fresh, frozen, or water-packed in a can. I mix them with oatmeal, cocoa, and mint leaves for a chocolate-covered-cherry type sensation. You may want to try that for a few days before participating in your next big sporting event.

Next up – we look at the pros and cons of fennel fruits as a cheap, easy-to-find, nonperishable source of nitrates.

Dozens of studies now suggest that the nitrates in vegetables, such as beets and green leafy vegetables, may help both sick people, as a low-cost prevention and treatment intervention for patients suffering from blood flow disorders, such as high blood pressure and peripheral vascular disease, as well as healthy people, as an effective, natural performance-enhancing aid for athletes. Most of the studies were done with beet juice, which is why I was so delighted to see a study on whole beets, as I reported before, showing the same benefit, but what about studies on whole green leafy vegetables?

 There was this study a while ago suggesting that one of the reasons that, at the age most Americans and Europeans are dying, the Okinawan Japanese are looking forward to many more years of good health, at least they were, is all the nitrate in their green leafy vegetables, which tends to bring down blood pressures when put to the test. The reason I didn’t report on it at the time is because I had never heard of these vegetables. I know what chrysanthemum flowers are, but I didn’t think most of my viewers would be able to find these at the local store.

What about good old American, red, white, and blue greens, like frozen spinach? It hadn’t been tested… until now. They wanted to test the immediate effects on our arteries of a single meal containing a cooked box of frozen spinach for both arterial stiffness and blood pressure. First, they needed a meal to increase artery stiffness and pressure; so, they gave people a chicken and cheese sandwich, which lowered the elasticity of their arteries within hours of eating, but add the spinach and the opposite happens. After chicken and cheese, the force the heart has to pump goes up within minutes, but the spinach keeps things level. So, a meal with lots of spinach can lower blood pressure and improve measures of arterial stiffness. That’s great for day-to-day cardiovascular health, but what if you want a whole food source that can improve your performance when you’re out hiking or something? Beets and spinach aren’t the most convenient of foods; is there anything we can just add to our trail mix?

If you look at the list of high nitrate vegetables, you’ll see there isn’t much that you can just stick in your pocket—unless, fennel seeds have a lot, which are actually not seeds, rather the whole little fruits of the fennel plant. Let’s find out. Fennel seeds are often used as mouth fresheners after a meal in both the Indian sub-continent and around the world. You’ll typically see a bowl of candy coated fennel seeds as you walk out of Indian restaurants.

 And when you chew fennel seeds you can get a significant bump in nitric oxide production, which has the predictable vasodilatory effect of opening up blood vessels, making them a cheap, easy way to carry a, light-weight, nonperishable source of nitrates. They single out mountaineers, thinking chewing fennel seeds could help maintain oxygen levels at high altitudes and help prevent H.A.P.E. (high altitude pulmonary edema), one of the leading killers of mountain climbers once you get more than like a mile and a half over sea level. Not to be confused with H.A.F.E caused by the expansion of gas at high altitudes, a condition known as High Altitude Flatus Expulsion, known to veteran back-packers as Rocky Mountain barking spiders.

But fennel seeds may help with that too, as traditionally, they’ve been used as a carminative, meaning a remedy for intestinal gas. Fennel has also shown antihirsutism activity, combatting excessive hair growth in women, the so-called bearded woman syndrome, but applying a little fennel seed cream can significantly reduce it. But if fennel seeds have such a strong hormonal effect, should we be worried about chewing them? Well, there have been cases reported of premature breast development among young girls drinking fennel seed tea a couple times a day for several months. Their estrogen levels were elevated, but after stopping the tea, their chests and hormone levels went back to normal.

Current guidelines recommend against prolonged use in vulnerable groups, children under 12, pregnant and breastfeeding women, and perhaps your pet rat, as rodents metabolize a compound in fennel called estragole into a carcinogen, but our cells appear able to detoxify it.

Finally today, what is the latest science on the performance-enhancing qualities of nitrate-rich vegetables? Let’s find out.

Nitrates, concentrated in green leafy vegetables and beets, underwent a great makeover a few years ago from inert substances to having profound effects on the power plants within all of our cells, reducing the oxygen cost during exercise—meaning we can bust out the same amount of work with less oxygen. So, one little shot of beet juice allows free divers to hold their breath for over four minutes; they get about a half-minute longer, and for others, this improved muscle efficiency allows athletes to exercise at a higher power output or running speed for the same amount of breath. I profiled this discovery in an unprecedented 17-part video series, the longest I think I’ve ever done—it was just so fascinating. But that was back in 2012; what’s happened since? Well, this all led to many athletes—elite and amateur alike—consuming beetroot juice prior to competition. But what does the new science say?

Well, most of the studies were done on men; turns out it works on women too—even African-American women, an even more neglected research demographic. Same workload power outputs using significantly less oxygen after drinking beet juice. But forget beet juice; what about whole beets? Cheaper; healthier; can find them in any produce aisle. But there had never been any studies on actual beets, until now.

Whole beetroot consumption acutely improves running performance. They gave physically fit men and women a cup and a half of baked beets, which is equal to about a can of beets, 75 minutes before running a 5K. They started out the same, but during the last mile of the 5K race, the beet group pulled ahead, compared to the placebo group, who were given berries instead.

Though they were running faster, their heart rate wasn’t any higher. If anything, the beet group reported less exertion. Faster time with less effort? They don’t call them block-rockin’ beets for nothing.

But if nitrates are so good, why not just take them in a pill? Nitrate supplements with names like “Hellfire”—although they can work, their long-term safety is questionable. Non-vegetable sources of nitrates may have detrimental health effects; so, if we want to improve our performance, we should ideally obtain nitrates from whole vegetables. The industry knows this, so instead markets an array of nitric oxide-stimulating supplements. However, there is little or no evidence of a performance improvement following supplementation with these so called NO boosters. The evidence is with the vegetables.

How much money can companies make selling beets though? So, how about a novel beetroot-enriched bread product? We’ve tried to get people to eat their fruits and vegetables, and where has that gotten us? But hey, lots of people eat white bread; why not have them eat red bread? And, indeed, it worked; red beet bread brought down blood pressures, and improved the ability of arteries to relax and dilate naturally. Bread, therefore, may be an effective vehicle to increase vegetable consumption without significant dietary changes, because heaven forbid people should have to change their diet to improve their health.

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