Answers to questions about smoothies, such as “why am I hungry after I have one?” And “what are good ways to make them more healthful?”

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ON NUTRITION

Smoothies are a delicious way to take advantage of fresh fruit in the summer or frozen fruit in the dark days of winter. The can also be a vehicle for dark leafy greens (hint, hint). But are they really as healthful as they seem? Let’s investigate.

Are smoothies a good way to get extra nutrients?

Nutrients in whole fruit and vegetables are trapped within fibrous cell walls. As we chew, our teeth and saliva start breaking down those walls to release the goodness within. The acid in our stomachs and digestive enzymes in our small intestines continue the process. Because some nutrients remain stubbornly bound to fiber in fruit and vegetables, you reap even more nutrients when yet-to-be digested fiber is fermented by bacteria in your large intestine (colon). Generally speaking, smaller particles release more nutrients, and your blender can chop your food into significantly smaller particles than your teeth ever could. This is of particular benefit with some antioxidants and phytonutrients, for which a smaller particle size may enhance absorption.

But does blending produce “kill” the fiber?

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Blending has one major advantage over juicing, in that you keep the fiber from your fruit and veggies, making smoothies a “whole” food in that respect. When you eat solid fruits and vegetables, some fiber makes it through to your colon undigested so your gut microbiota has something good to eat. But if your blender chops up that fiber into minute particles, will it get digested before it gets to your microbiota? Research says no.

Do smoothies spike your blood sugar?

When you eat a piece of whole fruit, its intact fiber slows digestion of the natural sugars inside the cell walls. When you drink juice, you get a concentrated dose of sugar without fiber to slow it down. But what happens when you break down those cell walls in a blender? Will this cause a sharper rise in blood sugar? With some fruits, the answer is yes. But with berries, a smoothie staple and one of the most nutritious fruits around? No. Research shows that blended berries promote stable blood sugar.

Why am I still hungry after I have a smoothie?

Our bodies tend to not notice calories from liquid the way we do from solid food. Studies have shown that eating whole fruit is more satisfying than drinking a smoothie, and drinking a smoothie is more satisfying than drinking juice. Oddly, studies also show that eating pureed vegetables in a soup is more satisfying than eating solid vegetables. Why would soup be different from a smoothie? It’s the way that you eat it. A Purdue University study served participants a solid fruit salad, a smoothie in a glass or a smoothie in a bowl, and found that the fruit salad and the smoothie in a bowl, which were eaten with a fork and spoon, respectively, left participants more satisfied than the smoothie drinkers. So there you go!

What should I put in a smoothie?

Just as it’s a good idea to limit juice intake, it’s best to avoid juice in your smoothie so it doesn’t turn into a sugar bomb. Better alternatives include unsweetened coconut water or plant-based milks (almond, soy, coconut), dairy milk, or kefir and yogurt, which also give you a probiotic boost.

Then, add some greens with your berries. Hesitant? Use spinach as a gateway green (it’s mild), test the waters by using one handful to start, then opt for dark berries (blueberries or blackberries) to hide any discoloration from the greens. Bon appétit!