We took a careful look at the evidence.
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If you've wandered the kitchen section of a department store in recent years, you may have noticed there's a sort of arms race going on among blender manufacturers to create the fastest spinning blades. Technically, these high-powered, industrial-grade machines aren't blenders at all, but emulsifiers—basically, that's any blender with a horsepower of 2 or higher.
Generally speaking, emulsifiers are supposed to be capable of shearing food into particles so small that a silky smooth concoction can even result even from ingredients that don't tend to play nice together—such as oil and water. They can also be useful for amateur chefs, who might want to make thick concoctions, such as nut butters, which could require some extra oomph on the blender's part. Or if you're a "texture freak" who wants "satiny-smooth purees and smoothies," as The Sweethome, a New York Times-owned gear review site, put it.
But the companies that market these machines like to say that high-speed blenders can do more than conquer notoriously difficult substances, such as mayonnaise and peanut butter. Often, they make claims that the blenders can "break open" greater nutritional benefits in your food. (More on that in a moment.) And with entry-level models like the BlendTec Classic 575 and Vitamix 5200 costing $420 and $450, respectively, you'd better hope that you're getting more than just a few extra RPM's.
These nutritional claims are often used as a sales tactic: In 2008, Vitamix's then-president (now executive chairman) John Barnard praised a scientific study that pitted an emulsifying blender against a household blender and a human mouth. He said Vitamix's "2 peak HP motor and new-generation container…work together to break open the cell walls of whole foods. That, according to a 2008 study conducted at the University of Toronto, enables the Vita-Mix machine to deliver maximum nutrition from fruits and vegetables."
Unfortunately, that University of Toronto study remains unpublished—and the link has been scrubbed from Vitamix's website, despite it being frequently mentioned on various wellness blogs. That could be because it's mostly a bunk claim, says Marion Nestle, professor of nutrition, food studies, and public health at New York University. "High-speed blending should make foods quicker to digest, at best, but that's all."
Her cohorts agree: High-speed blenders expose "the issue of food structure…and how people really know little about it," says Bruce German, director of the Foods for Health Institute at the University of California, Davis. Beyond the convenience factor, he adds, they're likely not doing anything more beneficial than the average $20 model from Wal-Mart—or your mouth.
Reached for comment, a Vitamix representative, Jamie Dalton, confirmed the existence of the 2008 study—as well as the accuracy of Barnard's quote—but added that the company's thinking on the subject has evolved in the years since. The focus now, she says, is "using Vitamix as a tool to really achieve the lifestyle you're looking for, instead of a more granular focus. It makes it easier to consume whole foods. It makes it easier for you to do whole food juicing, which is a different process where you get more nutrients versus traditional juicing, because you're keeping the pulp and the seeds and the skin and all of those things that really are beneficial to you."
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On this point, science is actually on her side: Research has shown there's at least a little bit of upside to grinding up whole foods—but there's also a point of diminishing return, and it's one you tend to reach without, well, 2 horsepower required. A study conducted in 2014 found that when common fruits like apple and pear are blended, peels and all, they have a higher antioxidant capacity compared to just blending their "flesh fraction."
But this study doesn't necessarily point to "broken open" nutrition on the part of the blender. It just points to the fact that whole foods deliver more nutrients. And that doesn't suggest mega-nutrition from "broken cell walls." And again, most normal blenders can mash up fruits and veggies just fine. Even your mouth can get you there, if you're a patient chewer.
Yet the Vitamix user's manual tells a different story, claiming that "the rugged blade assembly literally explodes molecules of food" and "tears down the cell walls of fruits and vegetables, making vital nutrients from peels, pulp, seeds and all, more readily available for your body to absorb."
Nutribullet, a competitor, puts similar claims in its user's manual, saying, "Even when we eat healthy foods, our digestive system does not break them down enough to release the full spectrum of vitamins, minerals, and phytonutrients they contain." To which Nestle and others say: Eh, not really. Large particles of food—like a corn kernel—might come out whole on the other end, says Joanne Slavin, a professor of food science and nutrition at the University of Minnesota. But that's not typical.
"Most everything by the time you chew it up has enough surface area to get well-processed in the body and broken down," she says. Blending whole fruits and veggies, she adds, really has the most benefit for infants, the elderly, and maybe perennially busy folks. "Why would you self-select to live on a liquid diet? You have teeth, enjoy them." (Nutribullet did not respond to multiple requests for comment.)
But even if your hectic schedule justifies a daily smoothie habit, it's actually smart to keep some texture in your food. "At the end of the day, some food structure is good, in that it slows the digestion and regulates everything else," German says. One 2007 study, among other research, notes that people had more balanced energy after solid meals versus liquid meals because they had lower levels of insulin and ghrelin, the hormones that regulate metabolism and appetite.
As for busting apart cell walls and such, well, the jury will remain out until the University of Toronto study gets peer-reviewed and published—or until someone else attempts it. So far, Slavin hasn't seen the evidence that it's true: "You'd have to show that to me in a microscope," she says. She says typical blenders have been used in every food analysis study she's ever participated in. For example, "to measure fiber, you first blend stuff up, and then you freeze dry it, and then you measure it. So every food analysis we blend stuff up, and that's the start."
What we do know is that the occasional smoothie can be beneficial if it replaces a mindless snack in favor of whole fruits and veggies. But when it comes to using speed to hasten a mega-nutritious transformation, the only certainty is convenience.
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