Green smoothies started showing up everywhere a couple years ago, followed quickly by the green juice craze. But wait — aren't those two the same thing? No, there is actually a key difference between smoothies and juices, and that difference has a big impact on how you digest the two.

So What's This Big Difference?

In a nutshell, the difference is fiber. Smoothies have a lot of it; juices typically have very little.

A smoothie is made by placing all the ingredients in a container and processing them together. Whether you use a high-powered blender like a Vitamix, a single-serve cup blender like the Magic Bullet, or an immersion blender, the results are the same: You consume the entirety of the fruits and vegetables that go into the mix, including the fiber.

A juicer, on the other hand, filters out much of the fiber from the fruits and vegetables you are juicing, leaving you with the liquid juice and the fibrous pulp, which is discarded. Some juicer models do allow you to regulate the amount of pulp (read: fiber) that ends up in your glass.

Why Does Fiber Matter?

Fiber helps slow digestion, keeping you feeling fuller longer and helping to stabilize blood sugar levels. It also feeds the microbes in your gut, which research is showing play a key role in our overall health.

There are two types of fiber, both of which are present in different types of fruits and vegetables. Insoluble fiber helps keep you regular, attracting water to the intestines and moving everything through your system. It is found in foods like cucumbers, celery, carrots, nuts, and seeds.

Soluble fiber has several health benefits, including helping to lower blood cholesterol, slowing the absorption of carbohydrates from foods, and feeding the beneficial bacteria in your gut. It is found in foods such as oats, apples, berries, plums, pears, nuts and seeds.

Does That Mean I Shouldn't Drink Juices?

The lack of fiber in juices gives them one advantage over smoothies: They cram in a lot more nutrients per serving. That can be a good thing during a week when you are feeling crummy and want a big serving of vegetables in a cup. Vegetable-based juices are a tasty, convenient way to get a lot of vitamins, minerals and phytonutrients in one go.

The downside is that some juices contain a large amount of sugar from fruit — without the fiber to help digest it slowly. And also, do you really need to consume a whole bundle of carrots or a mound of raw kale in one gulp on a daily basis? I'm not so sure.

The truth is, if you're like most Americans, you aren't getting enough fiber in your diet to begin with. Instead of tossing it out, why not make your daily "juice" in a blender (i.e., opt for a smoothie instead)?