Can a green smoothie transform your life? After watching 56 minutes of Powered by Green Smoothies, I had to say yes. In the new documentary by Sergei Boutenko, ten ultrarunners and CrossFitters kept their typical training and racing regimen unchanged but added a quart of green smoothies—packed with leafy greens and fruit—to their diet every day for six weeks. The result: Those who could follow the program experienced quicker recovery and significantly less soreness.
And we’re not talking just one less day of feeling sore: One participant ran a 100-miler and was logging 15-20 miles after only ten days off, instead of his typical month of recovery. Another runner found that he could run farther than a marathon without ever hitting that wall most people have to grind past—and he felt so good the next day that he went for a 10 mile run.
So how is this possible? “When you do any endurance activity, your body releases free radicals which damage your cells and cause oxidative stress,” says Matt Ruscigno, MPH, RD, an endurance athlete and leading expert on vegetarian nutrition, co-author of No Meat Athlete: Run on Plants and Discover Your Fittest, Fastest, Happiest Self. Phytochemicals—which include all compounds abundant in plant-based foods, like antioxidants, beta-carotene, and vitamins—help fight these free radicals, lowering inflammation, which reduces soreness and recovery time.
Lower inflammation may account for some of the smoothie’s benefits: Many of the CrossFitters in the documentary had existing injuries like sore shoulders and elbows, but after adding the green drink to their diet, their trouble spots started to fade and they were even able to do workouts their injuries normally prevented them from doing. And, when they stopped drinking smoothies after the six weeks, most of their aches started up again.
Depending on the athlete’s pre-documentary diet, the benefit could also simply come from the extra calories smoothies provide, says Lona Sandon, RD and certified fitness instructor, assistant professor of Clinical Nutrition at the University of Texas Southwestern Medical Center at Dallas. “A lot of CrossFitters tend to follow a high-protein, low-carb diet so they’re often shorting themselves on adequate carbohydrates—undermining their energy stores—and on fruit—and all their beneficial nutrients,” she says. And while runners know to carbo-load, many are still restrictive with their energy intake, and an extra 200-400 calories could give them a surprising boost, she adds.
The extra carbs probably account for one of the most interesting results of the documentary: The CrossFitters saw more improvement from their baseline endurance test than the runners did. Almost all the runners added an extra 200 meters to their original 12 minute lap test—which could make or break first place in a race—but the CrossFitters significantly improved the number of kettle bell swings, pull-ups, and sprints they could get through compared to six weeks before. Extra energy would allow the CrossFitter’s muscles to work longer before fatiguing, Sandon explains.
And while athletes may benefit from the vitamins and antioxidants of smoothies, keep it to whole food: High-dose supplements can actually hinder some benefits of high-intensity training, says Sandon. In fact, a recent study from the Norwegian School of Sport Sciences in Oslo found that after a grueling 11-week training program, athletes who had taken a high dose of antioxidants—specifically vitamin C and E—every day saw fewer biomarkers of beneficial fitness gains than athletes who trained sans supplements. This supports past research showing that high doses of inflammation-fighters actually lowers your body’s ability to produce beneficial compounds on its own and lower inflammation naturally, Sandon explains.
But are smoothies the best way to go? “Smoothies are a great way to get a lot of nutrients at once, because you’re blending more whole foods than you could eat in one sitting,” says Ruscigno. And you don’t need to drink a whole quart—which is four cups—to gain the perks: “Everyone could benefit from more fruits and vegetables in their diet, so even a 10-ounce smoothie still provides more fruits and vegetables than most people eat in a day.” If you already packing enough carbs and calories to support your training regimen, you might not see as big of a boost though, he warns.
And you don’t have to drink pure kale to see results: “Most of my participants weren’t big smoothie drinkers, so I started with 60 percent fruit, 40 percent leafy greens,” says Boutenko. “But within 6 weeks, their taste buds adjusted and by the end they were requesting more vegetables in the mix.”
To see how else green smoothies affected the endurance athletes, check out the documentary at PoweredByGreenSmoothies.com.