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To smoothie or not to smoothie? The skinny on blending your fruits and greens

Wednesday, January 18th, 2012

To smoothie or not to smoothie?  It’s the plant-based fitness expert’s blog.  Of course I’m going to tell you to cram as many greens and fruits in as you can, right?  Not so fast.

With an upsurge in ‘smoothies’ and ‘cleanses’ all over the web this time of year, for health, ‘detox’, or weight loss, it’s good to be mindful of why you might not want to make smoothies a part of your daily diet. Especially f you are trying to lose weight, or keep your weight in check, or have blood sugar and triglyceride challenges. Or satiety challenges for that matter.

2 big reasons you might want to limit smoothies

  • decreased satiety as compared to whole foods
  • increased destabilization of blood sugar compared to whole foods

Blending and whirring vegetables and fruits as happens in the making of smoothies disrupts the fiber of the natural food. This disruption impacts the satiety value of that food.  It seems, doesn’t it, that all of the fiber that was there before you blended it should be there in your smoothie.  After all, you didn’t extract the juice from  the apple, the spinach, the blueberries – you just blended it up.  Fiber is fiber, right?

It doesn’t work that way.  Disrupting the fiber, as happens in the process of making a smoothie, exposes more of the surface area of the food.  This means it  is absorbed more quickly, making it more likely that it will effect your blood sugar and insulin levels.  Not only that, but the more of it you want to consume.  When the food is whole, or even chopped, we have more invested in the project of eating by chewing, an important part of the digestive and satiety process.

Calorie consumption comparisons between whole foods, blended foods, and juiced foods with fiber restored

These numbers of analysis should help. Studies comparing caloric intake at a meal following the consumption of either nothing (no preload), an apple, applesauce, apple juice (with fiber added), apple juice (no fiber added) delivered the following results.

Though the apple, applesauce and apple juice with fiber all had the same amount of fiber, there was a clear (and significant difference) in the effect of these 3 forms of apple on satiety and caloric intake.

  • The whole apple decreased calorie intake by 15% in the meal that followed
  • The apple sauce decreased caloric intake by 6% in the meal that followed
  • The apple juice with fiber decreased calorie intake by  1% in the meal that followed.
  • The plain apple juice actually increased total caloric intake by 3%. *

Dramatic differences over time!

What is the take-away from this study?  There is a clear difference between the satiety delivered by whole fruit and foods in contrast to the same foods blended, where the fiber is disrupted.   I know that I can eat a whole lot of fruit if it’s blended.  And the numbers from the testing detailed above explains to me why a smoothie breakfast doesn’t stay with me nearly as long as a my breakfast bowl of steel-cut oats topped with chunks of fruit.

Does this mean you should never have a smoothie, or that they are ‘bad’ for you?  Settle down. On occasion they can provide a quick meal and I like my Vitamix fruit ice cream just as much as the next guy (frozen cherries with banana and carob.  Man!)

But if weight, blood sugar, and insulin levels are a concern to you, then the answer to the question “to smoothie or not to smoothie?” may be clearer.  Occasional?  Sure.  Every day?  Maybe not.

Dr. Caldwell Esselstyn says,

“Avoid smoothies. The fiber is so finely pureed that its helpful properties are destroyed. The sugar is stripped from the fruit, bypasses salivary digestion and results in a surge of glucose and the accompanying fructose contributes to inflammation and hypertension. “

This can probably be mitigated somewhat by limiting the amount of fruit and thinking ‘green drink’ rather than a smoothie packed with several pieces of fruit.

Show me the plants!

First and foremost, I’m interested in getting people to eat more plants.  And if digestion is a problem, or someone for some reason or another is unable to chew well, green smoothies with some fruit may provide a valuable source of nutrition.  It may serve as a way to draw children in to loving their greens (see Smoothie, the Movie).  And athletes may benefit from the large calorie load and fuel replenishment you can get in the form of a blended plant drink.

Thanks so much for coming by and share your thoughts below.  Please ‘like’ and share this post and if you’re on facebook, please join me now on my facebook page here: facebook.

*Resource:  The effect of fruit in different forms on energy intake and satiety at a meal Appetite, Volume 52, Issue 2, April 2009, Pages 416-422 Julie E. Flood-Obbagy, Barbara J. Rolls

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