Simple sugars and fruit juices: let’s shed some light


Disinformation is more contagious than gastro during the fall time (if you have little ones, you know what I mean). The massive growth of internet and social media has brought to the creation of erroneous beliefs that are hard to eradicate. Let’s be clear: I have nothing against media (I also use one of them!), they are powerful means allowing a rapid and effective communication. But it is actually because of their power that we should use them with consciousness. The net is so soaked with disinformation, in particular scientific disinformation, that I might spend the next 100 posts to speak about that (a good idea, when my inspiration is low! ;)).

But I am just wandering. The thing is the other day I had a debate on simple sugars and I realized how much confusion there is about that. I have already mentioned the topic in this post, but yesterday’s discussion has stimulated me to write an article dedicated to sugars in fruit juices.

There is the diffused and erroneous belief that sugars “naturally” contained in juices are of higher nutritional quality than those sold in packages, in every grocery store. When I speak about juices, I mean those obtained by squeezing or homogenization, without sugar added. The misunderstanding is always due to the bogus belief that, for example, the sucrose “naturally” contained in fruit is healthier than the commercial one (“industrial”). Based on this belief, marketing has built fruitful campaigns that have increased the profits of many companies, but didn’t significantly change the life of consumers. Please, follow me. The discussion is long and I will probably annoy you the chemical part of the story.  

Which are the sugars of the fruit

Differently from what most people think, fruit doesn’t contain only fructose, as sugar. For example, a fruit as banana contains a mix of fructose, glucose and sucrose. For the chemistry corner, here the structures of glucose, fructose and sucrose:

Both glucose and fructose consist of only one molecule and are, thus, called monosaccharides. Sugars as sucrose and lactose consists of two units and are classified as disaccharides. Glucose, fructose and sucrose are all simple sugars. This means that our body absorbs and uses them quickly.

The importance of sugars

The outbreaks of diseases as diabetes and obesity have warned about excessive sugar intake. However, we should remember that sugars and complex carbs are our fuel. Our body preferentially, but not exclusively, uses glucose as source of energy. Why? Simply, because the glucose metabolism is the most effective. Shortly, it was an evolutive adaptation. Would you fill diesel in a car that uses gasoline?

Simple sugars are rapidly absorbed and give energy immediately. Unfortunately, it is now well understood that an excess of simple sugars increases the risk of diabetes and obesity. Therefore, we should limit their intake!

What’s about fructose? Is it better than glucose?

Let’s define “better”. If we refer to the caloric intake, you should know that fructose brings as many calories as glucose. A certain type of fructose is often recommended in diets, because it owns a higher sweetening power than the glucose. Therefore, it can be used in lower amount by reducing the caloric intake. However, there are evidences that an excess of fructose promotes the development of diabetes and obesity, seemingly to any other simple sugar. Again, we should limit simple sugars’ intake.

What’s about fruit, then?

Fruit is an excellent food and, doubtlessly, snacking with fruit is a good habit. Fruit is relatively low in calories and contains fibers and vitamins. But...we should also consider the “form” of fruit we select... :)

The discussion that has inspired this post arose the other day, while my hubby was selecting a beverage to quench his thirst, during a hot summer’s Sunday. Grabbing a bottle of apple juice (the very transparent one ;)), he cried: “better a fruit juice that contains natural sugars!” Yes and no. Even if that juice is made with apples, you are not eating an actual apple.  Even if there are “no sugar added”, that juice contains simple sugars (glucose, fructose, sucrose), which are readily absorbed, as they are already extracted from the pulp. And there is no difference among those sugars, contained in the juice, and the crystalline ones you find in the grocery stores. Not to mention that the vitamin level in fruit juices (often fortified) is much lower than in the whole fruits. Unfortunately, most of the vitamins degrade easily and their concentration significantly decreases during processing and stocking.

The conclusion?

Long story short, simple sugars should be limited, dot. Fruit juices (even those without sugar added!) contain simple sugars, fructose, glucose and sucrose, already “extracted”, thus, rapidly absorbed by our body. Therefore, be careful with your choices. Selecting the whole fruit is definitely better.  


USDA Database,

V.S. Malik and F.B. Hu, Fructose and Cardiometabolic Health: What the Evidence from Sugar-Sweetened Beverages Tells Us, J Am Coll Cardiol. 2015, 66, 1615–1624

Stryer, Biochemistry, 339-341