To Smoothie or Not To Smoothie, That is the Question

As recently as March 1, 2016 Canada’s Senate Committee on Obesity declared "Canada’s dated food guide is no longer effective in providing nutritional guidance to Canadians. Fruit juice, for instance, is presented as a healthy item when it is little more than a soft drink without the bubbles." 

For me, this statement is an incredible victory for the science of fructose, the sugar found in fruit. Since 2009, when Dr. Robert Lustig’s YouTube video, Sugar: The Bitter Truth, went viral, the word fructose has conjured up much debate. Why? Because we now know through his research and others that fructose is metabolized only in the liver, and it is metabolized into fat when ingested in large quantities. 

That's right, the liver converts fructose to fat, and when your liver produces fat, it becomes insulin resistant. A fatty liver increases small, dense LDL cholesterol (the bad kind) and triglycerides. And the process by which this occurs produces uric acid as a byproduct, which leads to hypertension. A fatty liver, therefore, increases one’s risk for both cardiovascular disease and type 2 diabetes. 

Juice provides a concentrated dose of fructose and thus, it doesn't deserve the health halo it's been wearing for decades. As you can imagine, this news has not made the juice industry very happy.

I know what you're thinking: Is fruit as bad as juice? 

In his book, Fat Chance, Dr. Lustig explains the difference between the two is all in the fiber. 

Whereas fruit does contain fructose, it also has inherent fiber. The reason the fructose in fruit doesn’t cause significant health problems is that it’s balanced by the endogenous fiber that makes up the solid part of the fruit. If you consume both together, as Nature intended, it reduces the rate of flux to the liver; the liver can keep up, which mitigates most of the negative effects of the sugar. In fact, the amount of fructose in most fruits is balanced nicely by the fruit’s fiber content. Conversely, juice is devoid of the insoluble fibre found in whole vegetables and fruit. When “juicing,” you keep some of the essential vitamins and minerals (but not all) inherent in the fruit or vegetable, but you discard perhaps the most important part: the fiber. (page 133-134)

And what about fruit smoothies? 

Although you are using the whole fruit to make the smoothie,

the blades of the blender completely destroy the insoluble fiber of the fruit…. The sugar in the fruit will be absorbed just as fast as if the juice were strained with no fiber at all. Dr. Robert Lustig, Fat Chance, page 134 

Even if you add Greek yogurt as a source of protein, fruit smoothies are a crash and burn meal replacement. Most commercial smoothies are made with a concentrated fruit paste and sweetened yogurt. They are truly sugar bombs!

Homemade or not, fruit smoothies are just not a solution for a meal, and they are a potential metabolic disease activator.

What about shakes made with protein powder? 

When I tell my friends who are sipping protein powder shakes that they may not only be counterproductive to their health goals but could also cause fatty liver disease, I am usually politely (or not-so-politely) dismissed and asked why.

Dr. Lustig explained in a recent talk that the only place to store branched chain amino acids (from protein powder) is in muscle. If you’re building muscle like a bodybuilder, then consuming supplemental doses of BCAAs is fine. If you’re not building muscle, the BCAAs have nowhere to go but the liver. In the liver, BCAAs overwhelm the Krebs Cycle, fat is produced, and liver fat accumulates via a pathway eerily similar to that of fructose. 

This has been shown by Chris Newgard’s group at Duke University and described in the journal Cell Metabolism.

If you’re a bodybuilder and you take protein powder, have at it. If you’re not a bodybuilder, taking protein powder is counterproductive. Dr. Robert Lustig

Truly, I smiled when I heard that.

I would add: bodybuilders should still beware of how much protein powder they use. I have read about and seen bodybuilders and athletes using protein powder who were thin on the outside and fat of the inside (TOFI) with fatty liver disease and type 2 diabetes. Users beware…

And finally, the popular green smoothie. Good or bad? 

I asked Dr. Lustig directly. His answer:

Green smoothies don't have any appreciable sugar to slow down the absorption of. So if the only way you can get your veggies is a green smoothie, have at it. But eat the fruit.

As for me, I will pass on the green smoothie. I’ve tried many recipes—they just do not go down. I will take my mom’s advice on that one, “Eat your veggies or no TV!”


Chantal Bonneau is a Canadian Ambassador for the IRN. She lives in Montreal, province of Quebec. She has a BS in Kinesiology and MS in Exercise Physiology-Metabolism. Chantal is really passionate about real food! Check out her previous blog submissions:

Rethink Your Resolution

Negotiating Real Food with Your Family

Why I Teach My Nieces to Bake

Clean Eating Challenge - Family, Friends and Happiness

Eat Real Food

smoothie juice

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  • commented 2016-03-18 16:24:11 -0700
    So glad you are addressing this - the smoothie craze is sold on the assumption that this is great way to get healthy… you do a great job at de-bunking the smoothie mythology here.
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