Whole Fruit vs. Blended Fruit

Surely you know that smoothies are better for you than juices because they retain the fiber content of the fruit/vegetable, but have you asked yourself if a fruit smoothie has the same effect on your body as whole fruit? The answer may surprise you!

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This question came up today because a friend of mine has been on Weight Watchers for the past few months, and she was recently switched from PointsPlus to the new SmartPoints program. Under PointsPlus, most fruits and vegetables counted as zero point foods. With the updated points system, whole fruit is still zero points, but blended fruit (i.e. fruit in smoothies) has a SmartPoints value.

My friend said she and everyone else at her Weight Watchers meeting were very frustrated at this change. After all, fruit in a smoothie still technically contains the whole fruit! What gives?

If you’ve been wondering the same thing, I tried to dig up some science to explain it. It surprised me that there isn’t more evidence available documenting the effect of blending a food on glycemic index, satiety, and nutrient absorption. Here’s what I found, though:

  1. A 2007 study published in the International Journal of Obesity studied the effect of liquid meals vs. solid meals on satiety. The results showed that participants consumed on average 12% more calories per day when drinking a carbohydrate-rich drink. This suggests that drinking a blended fruit smoothie is less filling than eating a calorically equivalent portion of fruit. This is likely attributed to the fact that eating fruit takes longer than drinking it. Satiety signals are released as a hormones from the gut, and these must circulate through the bloodstream to your brain before you realize you’re full. That’s why waiting 15-20 minutes after eating a meal before deciding to eat a second helping is a good practice to adopt to avoid overeating.
  2. Chewing increases satiety. This has been documented in a study published in The British Journal of Nutrition in 2013. More chewing led to an increase in secretion of CCK in the gut (hormone that decreases appetite) and decreased secretion of ghrelin (hormone that increases appetite).
  3. Blending fruit changes the insoluble fiber contained in it. While it’s not accurate to say that blending fruit “destroys” the fiber, it does “change” it by breaking it into smaller particles. When you break the fiber compounds into smaller pieces, different things can happen, as explained in The Journal of Food Science article here. This is where the science gets sparse. Robert Lustig, MD, professor of pediatrics at University of California, suggests that blending fruit fiber has a negative effect on the glycemic index of foods. “The blades destroy the insoluble fiber, which means that the ‘gel’ that forms on the inside of the intestine has no structure. The sugar is absorbed at a maximal rate, overwhelming the liver’s capacity to metabolize the sugar, and the excess sugar is turned into liver fat which is the precursor to metabolic syndrome.” (Quote from Time magazine article April, 2015) That sounds reasonable to me, but I would much prefer a peer reviewed article cited to back that claim up!
    **If you want to completely nerd out over the food science of stuff that affects glycemic index, read this as well.

These factors combined help to explain why eating the whole, unprocessed version of a food is more filling than eating a blended, juiced, or puffed version of it. This also helps to explain why pureed or blended fruits have SmartPoints under the new Weight Watchers program. I hope that helps clear things up! Hit me up in the comments if you’d like to see more questions like this answered in the future.

References:

International Journal of Obesity (2007) 31, 1688–1695; doi:10.1038/sj.ijo.0803667; published online 19 June 2007

Zhu Y, Hsu WH & Hollis JH (2013). Increasing the number of masticatory cycles is associated with reduced appetite and altered postprandial plasma concentrations of gut hormones, insulin and glucose. British Journal of Nutrition 110: 384–390.

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Pumpkin Pie Smoothie

Indulge in pumpkin pie goodness without the guilt! This recipe is easy, creamy, and refreshingly chilly. The pumpkin is rich in potassium and beta carotene, while the greek yogurt delivers a good dose of protein!

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Ingredients:
1/3 cup frozen pumpkin purée (freeze in ice cube tray or ziplock bag)
1/2 cup plain greek yogurt
1/2 cup milk
1 tsp vanilla extract
1-2 packets stevia
1/8 tsp cinnamon
Dash of nutmeg, clove, and ginger (optional)
For topping: Crushed graham cracker and whipped cream (optional)

1. Blend all ingredients together until smooth, split between two glasses, and top with whipped cream and crushed graham cracker!

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Kiwi Spinach Green Smoothie

I usually make very basic green smoothies. The only ingredients are green apples and spinach. Today I decided to add a little something special- kiwi! This exotic fruit is rich in potassium, vitamin C, and natural protein digesting enzyme, actinidain. It’s also one of the lowest pesticide containing conventionally grown foods, so you don’t have to buy organic. Here’s how to make a super green smoothie with it:

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Ingredients:
1 kiwi, no need to peel!
1/2 green apple
1 handful baby spinach
1 tsp lemon juice
1/2 c water
Handful of ice cubes

1. Combine all ingredients in a powerful blender and gradually increase speed from low to high until very smooth. Serve immediately.

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I still have lots of kiwi to use up. That’s what I get for buying it at Costco! Maybe I will come up with more kiwi recipes. For now, I’ll be enjoying more of these refreshing green smoothies.

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Fresh Pineapple Smoothie

This pineapple smoothie is creamy and refreshing. The sweetness of the fresh cut pineapple balances the tanginess of the Greek yogurt. It’s gulp-able and reminds me of the fruity lassi drinks you get at Indian restaurants. Enjoy this protein rich drink poolside!

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Ingredients:
1 cup fresh pineapple, cubed
1/2 cup plain greek yogurt
3/4 cup ice cubes

Combine all ingredients in a high powered blender and pulse until smooth. Add extra pineapple for sweetness or more yogurt for tartness.

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Make a Perfect Smoothie

Good morning! Today I took a trip to Jamba Juice to get inspired for the next week or two of recipes for Karolina’s Kitchen. I’ll be posting lots of healthy protein shake and smoothie concoctions for you!

Jamba Juice gave me some ideas to get started.

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There are lots of great choices on the menu- smoothies, breakfast wraps, oatmeal… But what caught my eye today were the yogurt parfait toppers.

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I like that these are part smoothie and part parfait. Frozen fruit is blended with nonfat greek yogurt and topped with granola and banana slices for a smoothie that has some extra bite to it. I picked the 12 oz berry topper. The chunky strawberry banana topper (with fruit and peanut butter) sounded great, too!

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Yum! As I was enjoying my snack, I checked out their “boosts” brochure. Boosts are options you can add to your smoothie to customize it. You can add soy or whey protein, Greek yogurt, chia seeds, caffeine, multivitamins, oats, or immunity boosting zinc and vitamin C to your smoothie. I’ll be putting boosts in my creations, too!

The boosts I plan to use are:
-Chia seeds
-Ground flax
-Whey protein isolate
-Greek yogurt
-Nut butter
-Oats
-Spinach

Check back for smoothie recipes soon! Until then here’s how to make a perfect smoothie every time:
– 1 – 1.5 cups of fruit
– 1/4 – 1/2 cup greek yogurt
– 1/2 – 1 cup liquid

Happy creating!