Current dietary guidelines often treat the sugar in fruit juice and the sugar in sweetened beverages as “metabolic twins.” The World Health Organization (WHO) classifies both as “free sugars,” a label that suggests these sugars behave the same way in the body and enter the bloodstream at the same speed and in the same amounts, producing the same physiological response.
However, this classification overlooks the complex, nutrient-rich environment known as the food matrix, sometimes referred to as the “matrix effect.” A food’s matrix is the complex structural and chemical environment created by the nutrients it contains. It is not simply a list of components, but also the way those components interact with one another.
In a recent study conducted by researchers at the Centro de Edafología y Biología Aplicada del Segura, scientists sought to determine whether the sugars in freshly squeezed orange juice are absorbed differently from those in a beverage containing only those same sugars.
To investigate this, they compared the effects of consuming four 300 mL beverages in 25 healthy young men. Three of the beverages were adjusted to contain 25 grams of a sugar mixture composed of glucose, fructose, and sucrose: freshly squeezed orange juice, an orange juice drink with 50% added sugars, a sweetened water beverage, and a glucose-water drink.
The results, published in Food & Function, showed that blood glucose levels were significantly lower 15 minutes after drinking freshly squeezed orange juice than after consuming the sugary liquid. According to the researchers, “The presence of the fruit’s natural matrix acted as a regulator, moderating both the speed and intensity of the rise in blood sugar.”
This effect may be explained by the action of polyphenols such as hesperidin, which interfere with intestinal glucose transporters; minerals such as potassium, magnesium, and calcium, which support glucose metabolism; and factors such as acidity and residual fiber, which slow gastric emptying.
These findings challenge the assumption that all sugar is absorbed in the same way, revealing that the fruit matrix functions as an internal regulatory system that helps blunt glucose spikes.
“People often assume that because fruit juice contains naturally occurring fruit sugars, it must behave the same way as a sugary drink. Our findings clearly show that this is not the case. Food structure matters,” said Professor Francisco A. Tomás-Barberán of CEBAS-CSIC and lead author of the study. “Although public health recommendations often group all free sugars together, our work shows that the sugars naturally present in fruit juices do not produce the same metabolic response.”
The nutritionist’s perspective
According to British nutritionist Carrie Ruxton, “The matrix of freshly squeezed orange juice slows the absorption of sugars, creating a more gradual rise in blood glucose levels. This results in a more sustained release of energy after having a glass of juice with breakfast.”
“Freshly squeezed orange juice also contains vitamin C, which supports immune function and skin health; potassium, which helps regulate blood pressure; and a variety of fruit bioactives that support cognitive and cardiovascular function,” she added.
The study also found that not all participants responded in the same way. Researchers identified two profiles: high responders, in whom orange juice clearly reduced glucose spikes compared with the sugary beverage, and low responders, who showed only minimal differences between the two drinks.
Using advanced metabolomics techniques, the team found that these differences may be linked to how each person’s body metabolizes the juice’s bioactive compounds. Some individuals may deactivate the polyphenols responsible for slowing glucose absorption more quickly, thereby reducing their regulatory effect.
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