The Truth About Fruit Smoothies

In 1998, I went for a morning workout after hitting a fruit smoothie place and Starbucks. I figured, a little caffeine, a little healthy fruit smoothie action, and BAM! Plenty of energy to build the guns. What a horrible gastronomic gargantuan mistake that was. Between the smoothie and the coffee, my workout lasted about 10 mins.

It didn’t hit me then that a fruit smoothie and coffee could crush a workout like that. I thought, its crushed fruit, yogurt and juice, it has to be good for you right? Wrong. Between skyrocketing my blood sugar and amplifying that with a mocha (double shot no less + more sugar!) I annihilated my physiology to the point where I started shaking forcing me to stop the workout. Keeping in mind this was pure operator error, but it illustrates an extreme example of what can happen why you blow your blood sugar sky high.

I learned the hard way that a “healthy” smoothy is loaded with sugar, and very often can have more sugar than a 12oz can of coke (39g/can). That number has the potential to go up as high as 95g of sugar depending on if you add any  “boosts.”

Now, I’m not a registered dietician or nutritionist, but I’ve got a decent understanding of how the body works at this level, and I’ve heard Dr. Clyde Wilson talk, andI’ve read his research,  so I think I’ve got a better idea than most. I know a massive influx of sugar (regardless of its fructose or sucrose) into your body spikes your blood sugar in a manner that is nothing but bad news.

So, you’re looking for a healthy snack, and in the process you have the potential to put well over two cans of Coke’s worth of sugar in your body. Sign me up! Do it often enough, and that amount of sugar will add weight on you like nobodies business and here’s why.

“The faster sugar enters the bloodstream, the less goes to muscle, and the more goes to fat,” says Dr Wilson in his book What, When and Water: Nutrition for Weight Loss Wellness. “Eating rapidly digesting carbs will spike blood sugar and insulin levels resulting in a blood sugar crash with an increased hunger once the sugars are cleared into fat stores.”

Wilson also says when you replace a natural food with a processed food (juicing falls into this category) you “reduce the fiber and nutrient content significantly and make the resulting food one step closer to pure sugar.”

Microbiologist and NASM-CPT Lea Swenson agrees with Wilson.

You get the most benefit by eating fruits and vegetables in their ‘raw’ state.  When you juice a fruit or a vegetable you remove all of its fiber and bulk (as well as increase oxidation, thereby destroying nutrients),” she said. “The bulk is there for satiety and keeps us from eating 7 apples at a time and the fiber acts as a ‘control valve’ for releasing
glucose into our bloodstream.”  

By ingesting foods in a juiced state, you violate the glycemic index (GI is a measure of the effects of carbohydrates in food on blood sugar levels) in big way. Foods with protein and fat have a much lower GI rating than those with simple sugars

Swenson also said if you “flood the bloodstream with sugar and your pancreas floods your bloodstream with insulin in an attempt to deliver the glucose to your cells.”

Do this enough, and you become “insulin resistant.” When this happens, your muscles will absorb fewer calories. The ones your body does absorb have a much higher likelihood of going straight to fat storage.

“Circulating glucose fuels our brain (continuously) and goes to short-term storage in the liver and muscles as glycogen, ” says Swenson. “Once these glycogen stores are full the excess goes to long-term storage as fat.”

If you have a hard time losing weight when you’ve got carbohydrates in your diet, you are probably insulin resistant or your body may be addicted to sugar. There is a way around this.

Dr Wilson suggests if you are having a hard time losing weight, you should:

1) Only use legumes as your starch.

2) Temporarily eliminate grains, rice and potatoes from your diet.

3) If you are going to have a dessert, have a LARGE dark green salad prior to to slow the rate at which your body absorbs food.


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  • Al Painter

    I got this from Dr Wilson the other day:
    “The health impact of sugars is not dependent on how much sugar you eat, but how fast sugar enters the blood stream. When it comes to liquids (juice or blends), the sugars go to the bloodstream fast, so the more you eat the worse the effect (this is the opposite of eating vegetables, which improve their effects when you eat more even though the calories from them goes up). I met with one of the founders of Jamba Juice in January; his knowledge of nutrition was severely limited (I was surprised).”

  • Al Painter

    Commercial smoothie joints were the primary target for the article!!

  • Oh and btw, potatoes are healthy for you, too, but only if you avoid frying them and eat them with the skins ON. Additionally, the GI is lower when you eat them cooled.

  • Nice information you have supplied Rapunzel and you are right when you say not “all” juices etc are bad for us. Takes a lot of work to figure our bodies out and for what will/wont work :)

  • I have to share and clarify a few things that may cause a “regular” reader some confusion. First off, a smoothie you get at some smoothie bar or (HEAVEN FORBID) at Sbux (::fishslap::) is NOT healthy! HOWEVER, that does NOT mean all smoothies call into that category! If someone were to read your post and not have their own research or training, they might easily make that assumption.

    In fact, smoothies can be very healthy when done correctly. I make a smoothie for breakfast every day. (Occasionally, I juice my own fruits as breakfast.) Ever since I made the change from eating a grain and/or egg+cheese kind of breakfast to this fresh (or fresh-frozen fruits) for breakfast, I’ve felt much, much better. (Granted, I do not mean to imply that everyone should do this. It might work for some–like me–but not others.)

    What do I put in mine? I never, ever use a juice I bought in a jar, plastic bottle, or carton. EVER. Filtered reverse-osmosis water is the base in my all smoothies – loads of it. I put in half of a fresh avocado, a mixture of berries, maybe a 1 teaspoon of local honey [only 20 calories] and some real stevia. [Not the “-uvia” crap.] I often add some chlorella and sometimes cooked sweet potato or yam…or a veggie or two. That’s about it. Depending on the day, this smoothie comes to a grand total of ~250-275 calories. If I add some veggie protein, it might jump up an extra 30-50 calories, but I don’t use protein powders much b/c of how my kidneys react. (Side story that’s not related to this post.)

    Now before I made tremendous, wholesale changes to my diet 10 years ago, I used to have a regular problem with hypoglycemia. This was a problem that went back to my childhood…and yes, it was confirmed by that dreaded 5 hour glucose test. (That was one of the worst experiences of my life.) Prior to making such huge changes, I still ate what I considered to be a fairly healthy diet, and I avoided junk foods and drive-throughs. I watched my sugar intakes, ate plenty of protein to balance my sugar processing, etc. All that stuff. I was very sensitive to certain types of sugar and could tell when something would “set me off”. I share all this, because with the changes I’ve made, raw, local honey no longer makes me react – not at all. Nor does a fresh juice – as in it was juiced only a minute or two prior to when I consumed it.

    Not all juices are evil. If you buy one that’s pasteurized and is in a jar, bottle or carton, you are drinking loads of sugar. All the good enzymes have been destroyed, and most of the nutrients have been destroyed, too. Enzymes are killed off starting at 105 degrees and all are destroyed at 118+ degrees. Depending on what study you read, at least 30% and up to 70% of nutrients are destroyed by cooking and/or pasteurization. Let it sit on the shelf for a while longer, and the nutrients left in the container are even less. Better to toss those juice containers and drink a good quality water, instead.

    If you are going to drink juice, a fresh juice made using a low-speed juicer is best. (I use one that has a single auger and is able to juice just about anything, including wheat grass.) High speed juicers introduce high amounts of oxidation. To give you an example: Before I had a quality juicer, OJ made with one of those cheap, high-speed machines would oxidize [meaning nutrients and enzymes are lost] within 10 minutes. Once those ten minutes were up, the OJ had turned sour and was inedible/not drinkable. Only very small amounts of oxidation are introduced with a low-speed juicer. So, most of the nutrients and enzymes are retained

    When you do juicing correctly, you can get concentrated nutrients, and by making good choices, you can keep your sugar intake low.

    Also please note that fructose in a pasteurized/cooked juice will affect the body very differently from a “raw”, fresh juice. Once again, I do not react at all to fresh juices, no matter the amount. However on the very rare occasion that should I make the mistake of taking in a packaged juice, my body will react, unpleasantly. Bleah, no thanks.

    With the riding season in full swing, I like to make different variations of a fruit & veggie juice. With the high mileage I tend to do and in the temps in which many of these rides occur, my body needs higher levels of nutrients. Juicing is how I can accomplish this w/o taking in extra meals (and more calories than I need). Also, I notice the difference in how I feel and how hungry I am, overall. Does that sound weird? Well, that’s because when your body is in need of a certain nutrient (or several nutrients), it will stir your cravings, even if you just ate. It makes you think you are hungry when logically, you shouldn’t be. [Side note: Too little intake of water will cause your body to do the same thing.] I find that when I take in a dose of a fruit & veggie juice that those cravings disappear in short order.

    Keep in mind that most of us are deficient in potassium. This is true of nearly all Americans. For those of us who ride more than an hour at a time, our potassium needs greatly increase.

    During the winter and early spring, I had bouts of muscle weakness. At first, I couldn’t figure it out. After some research and trial-and-error, I finally realized that my potassium levels were way too low. (Duh! It was staring me in the face, but it took “hit by a barn door” to get my attention to figure it out.) Once I handled the issue, the muscle weakness disappeared. How did I handle it? By consuming certain vegetables and fruits that are high in potassium (as well as other nutrients of course). Sure, I could eat them whole. However, my body needed a great deal, and I do eat plenty of fruits and vegetables, already. My body needed concentrated doses. So, I juiced them. Presto, issued solved. Within a couple of days, I felt like a different person!

    My juicer and my Vita-Mix are vital elements in my kitchen!

    Okay…I’m done…for now. :-)

  • This is great info Al! Thanks for keeping us pointed toward the healthy path!

  • Great article as always Al :)

    Sugar really is a major problem in todays societies and it seems a lot of people who exercise are not aware of its pitfalls, either short or long term.

    I know for myself that sugar is not a friend of my bodies systems and therefore I avoid it as much as I can.