by Alejandra "Alex" Ruani — Get free science updates here.
I get this asked a lot:
“What’s WRONG with freshly-made natural fruit juices and smoothies?”
Let me start by telling you that, luckily, in nutrition science there are NO black-and-white answers.
I say “luckily” because the direction of nutrition isn’t blanket advice. It’s personalisation. Your genetics, your needs (biochemical, etc.), your goals, and your preferences all count.
So what’s wrong for you, is probably RIGHT for someone else.
And when it comes to the sugar in fruit juices and smoothies, it depends on the scenario, including the type of drink.
Let’s begin with a practical and very visual analysis of the sugar in a smoothie.
How “innocent” is this smoothie?
I have picked an Innocent smoothie label to illustrate this for you.
This is the nutritional information of an apple and blackcurrant serving of 180ml (1 small glass). Take a look:
Can you see the red arrow? With it, I’ve pointed the amount of “free sugars” in a 180ml glass.
In essence, you get 18 grams of “free sugars” in this small smoothie glass.
So not all 180ml are pure sugar. There are just 18 grams of “free sugars” in this glass.
Sounds like just a “little bit” of sugar, right?
18 grams of sugar in just one glass is a LOT of free sugars.
Now you may wonder: What are “free sugars”? And what amount is too much?
Free sugars 101
Basically, “free sugars” are:
- sugars that have been added to your food, OR
- those sugars which are naturally present in honey, in syrup, or in unsweetened fruit juices.
So yes, fresh juices and smoothies DO count towards your daily limit of free sugars.
What about fruit?
Whole fruits don’t count as “free sugars”. But fruit juices do, even that freshly-squeezed orange juice.
The UK’s Scientific Advisory Committee on Nutrition recommends that “free sugars” should be no more than 5% of your daily calories.
You can find the complete “free sugars” guidelines here.
For the average adult, that’s no more than about 25 grams of free sugars a day.
Remember the amount of free sugars that you’d get from our smoothie example?
18 grams. So drinking this small glass nearly maxes-out our daily limit…
But I think we can personalise things a bit further, and calculate your very own limit of free-sugars in grams.
Ready for some maths? Grab a pen!
How to calculate your free-sugars limit
Here’s how you can calculate your free-sugars intake limit per day:
1. Roughly assess your daily caloric needs.
My daily caloric needs: _____________ calories a day
For practical purposes, let’s say Susy needs 1,800 calories a day.
2. Multiply your daily caloric needs times 0.05 (that’s 5%).
So __________ calories a day x 0.05
The result is your upper limit of calories from free sugars.
In the case of Susy, 1,800 calories x 0.05 = 90 calories.
So, 90 calories is Susy’s daily limit of calories from free sugars.
3. Now divide those calories from free sugars by 4.
___________ calories from free sugars ÷ 4
This will give you your daily limit of free-sugars grams.
In the case of Susy, 90 calories ÷ 4 = 22.5 grams
Which means that Susy’s daily limit of free sugars is 22.5 grams.
Remember: These grams of free sugars a day is not an intake requirement to meet, but rather an upper limit that should not be exceeded!
The exception: endurance athletes
Endurance athletes who, based on more complex formulas, may benefit from a calculated supply of free sugars during a competition.
Think triathlons, ultra-marathons, Tour de France, and so on.
Most of the “free sugars” in fruit juices and smoothies are fructose.
But fructose metabolism tends to differ from person to person.
Okay, so we were saying that your body may metabolise fructose differently at this point in time.
In a more extreme example, the Inuit population (Eskimos) have difficulty metabolising sucrose (fructose and glucose). Imagine that…
This is due to an inherited gene mutation; a condition known as congenital sucrase-ismaltase deficiency.
Note: Unsurprisingly, humans in cold Arctic areas evolved with limited plant-based resources. So that may partly explain why fructose is seen as an offending substance rather than a fuel in these individuals. To get a taste for what Paleolithic humans really ate, go here.
So, how active are you?
Although fructose from drinks is one of the culprits for the current obesity epidemic, it’s not the fructose on its own to be blamed… but rather its excessive consumption (relative to your overall diet, lifestyle, and activity levels).
Hence, if you aren’t an active person, keep an eye on not exceeding the free sugars limit we talked about before.
Now you know how to calculate them!
Note: Excess fructose does have a role in increasing your fat stores. To understand how, first you need to learn how fructose metabolism works. Go here to see how.
Fresh juices vs smoothies
I love to hear from students who run their own juicing and smoothie businesses.
Packed with vitamins and phytochemicals, these drinks can provide potent health benefits – smoothies in particular.
A smoothie with a high-fibre content allows for the sugars to be more slowly absorbed into the bloodstream. That’s desirable for those who need to keep an eye on their blood-sugar management, mental focus, AND cravings.
A quick, large influx of sugar into your bloodstream can make you hungrier. So if you have a good amount of fibre in the mix, it can help slow down the absorption of fructose.
When you’re inactive, a slow and gradual absorption ensures that your food cravings don’t spiral upwards.
But blood sugar control is just one part of the process…
Brain reward needs to be considered too.
A 2015 study found that a high-fructose, fibre-free drink activates reward regions in the brain that make you more likely to seek out food and eat more.
Another good reason to keep an eye on the amount of free sugars and fibre.
Fibre, the ‘friendly’ polyphenol trafficker
There’s another added benefit from fibre that most people don’t know.
The plant fibres in smoothies encapsulate the beneficial antioxidants, protecting them from being destroyed by stomach acid, so more of them can reach your intestines.
A 2012 study shows that after antioxidants like polyphenols are released from the plant cell, up to 80% of them bind to the plant fibre. So, if you discard the pulp, you’ll be discarding those beneficial antioxidants!
Contrary to popular belief, fibre allows those antioxidants to be more bioavailable in your large intestines. So we’re now investigating how this action may help lower colon cancer risk, for instance.
Free sugars in smoothies
The one thing consumers need to be made aware of is the amount of total “free sugars” they consume per day.
Although homemade smoothies and fresh juices may not have “added” sugars, they do have natural “free sugars”, which still count towards the recommended intake limit.
So if you love smoothies, perhaps it’s just a matter of choosing the best one for you. Or maybe prepare them at home so you know what goes in each glass.
Let’s now take some smoothie labels for comparison.
Remember that the free sugars in a glass of apple and blackcurrant totalled 18 grams?
That’s mostly from the apple juice.
Manufacturers tend to go overboard with the addition of apple or pineapple juice.
They do that for palatability, so the drink tastes sweeter and less bitter.
How much apple juice was in our glass of apple and blackcurrant smoothie?
A pressed apple provided 70% of the drink.
So this commercial smoothie (marketed to kids) doesn’t have “added” sugars, but has a preposterous amount of “free” sugars.
Then our next question is, can we find a commercial smoothie with LESS apple juice, or with less free sugars?
I checked, and most Innocent smoothies have at least 18 grams of free sugars per 180ml.
Others have much more.
Like this one, with pomegranate, blueberry and acai:
No more than 5% of your daily calories should come from free sugars.
That’s NOT a target. It’s a limit!
You’ve also learned how to calculate your own free-sugars daily limit, by using the step-by-step formula I gave you, including a practical example.
Watch the labels of commercial smoothies to ensure you don’t surpass your daily sugar limit.
Since manufacturers tend to overdo the apple juice percentage, a better idea is to prepare your smoothies at home – or get them from a store where you can see what they put in them.
And if you run your own juicing and smoothies business, customers like me would love to know what goes in them, nutritionally. Free sugars and fibre content are the first two things I’d look for.
Are you a juicing or smoothie lover? Do you run your own juicing or smoothie biz? Tell me in the comments!
And if you’re on Instagram, share your next pic with the hashtag: #TheHealthSciencesAcademy – and I’ll be sure to check it out!
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