Does Blending Destroy Fiber?
Smoothies are all the rage, but how does liquefying fruits and vegetables affect their nutritional benefits? Nutrition Diva gets to the bottom of the glass.
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Oat bran on the other hand soaks up more water when you reduce the particle size. There's also some research suggesting that grinding up vegetable fiber into smaller pieces makes it more effective in reducing cholesterol.
So, I don't know that we can say that blending "destroys" fiber. But we can certainly conclude that blending "changes" fiber in foods and how they affect the body. Based on my brief tour through the literature, I think I would avoid putting wheat bran in my smoothie. Flax seed, on the other hand, is really only useful as a source of fiber if you grind it (or chew it up really well). Coarsely ground flax appears to be slightly more effective than finely ground flax...so don't overdo it.
Does Blending or Juicing Make Nutrients More Available?
But what about this idea that blending fruits and vegetables releases their nutrients? Although I wondered whether cells would be far too tiny to be affected by a blender, Lee assures me that scientists use blenders to break up cell wells all the time. (They also use heat, enzymes, acids, and other methods to rough up the little guys.)
And, indeed, there is some research showing that certain nutrients in fruits and vegetables may be better absorbed from juice than from whole foods. This may be, in part, because the nutrients have been "released" from their cells. But with juice you've also removed most of the fiber. As helpful as fiber can be in cleaning out the digestive tract, it also traps some nutrients along with the debris. In my opinion, this is usually worth the trade-off.
Assuming that your diet contains a good amount and variety of fruits and vegetables (and for those worrying about the cell wall integrity of their vegetables and particle size of their fiber--I'm guessing this is a safe assumption), squeezing every last microgram of beta-carotene out of every carrot doesn't really add that much additional benefit (although it can turn your skin orange).
Does Blending Foods Make them Better or Worse For You?
I'm afraid there's no simple answer. Blending or juicing foods can make certain nutrients more absorbable. It may decrease the effectiveness of some fibers but increase the effectiveness of others. Honestly, I think this falls into the (rather large) category of things that probably aren't worth worrying about. If you enjoy smoothies or fresh juice, feel free to include them in the rotation. They can be a good source of nutrition. And for tips on how to get the most out of them, please see my previous episodes on How to Make the Perfect Smoothie and Juicing for Health and Nutrition
But I wouldn't suggest liquifying all of your fruits and vegetables. Eating solid foods provides other benefits, such as increased satiation and satiety and better blood sugar control. The debate over whole fruits vs. juice reminds me a bit of the debate over raw food diets. While raw foods have some nutritional advantages, cooking foods provides other benefits. For best results, include both in your diet!
See also Moderation in All Things (Part 1)
What Do You Think?
I'd love to hear your thoughts on this or any other nutrition topic. Post them below or on the Nutrition Diva Facebook page. And please sign up for my free weekly newsletter for more tips, recipes, and answers to listener questions.