Cola Zero & Co.: Sweeteners, intestinal flora and metabolism

Why “sugar-free” doesn’t mean “ineffective”

Introduction

Coke Zero, diet sodas, and sugar-free energy drinks have long since become a staple in everyday life. They promise full flavor without the calories – and are often seen as a healthier alternative to traditional soft drinks. But biochemistry shows that sweeteners are not invisible. They interact with our intestinal flora and thus also with our metabolism.

Natural Foods: The Power of the Matrix

In fruit, vegetables, meat or cheese, nutrients are never present in isolation, but are part of a matrix :

• Sugar in apples is combined with fiber and vitamins.
• Phosphates in cheese are bound to calcium and proteins.
• Caffeine in coffee is accompanied by hundreds of plant compounds that influence its effects.

This matrix acts like a biochemical orchestra : it determines how quickly nutrients are absorbed, modulates blood sugar reactions, protects against overload and supplies the intestinal flora with important substrates.

Diet drinks: Isolated molecules

In Coke Zero and similar drinks, things are different:

• Sweeteners such as aspartame or acesulfame-K are isolated and freely soluble.
• Phosphoric acid is added, not bound to calcium like in cheese.
• Caffeine stands alone, without the polyphenols that normally accompany it in coffee.

Such substances therefore come into contact with our digestive system more directly and in a less modulated manner .

Sweeteners and the intestinal flora

The intestinal flora —the billions of bacteria in our gut—is now recognized as a key player in metabolism. Numerous human studies show that even normal amounts of sweeteners can alter the composition of the microbiome.

These changes are measurable—they can be detected directly in stool. And one thing is also clear: a change in the microbiome is never neutral.

Bacteria constantly produce metabolic products that enter the bloodstream or the intestinal mucosa. These substances influence blood sugar, lipid metabolism, the immune system, and even communication between the gut and the brain. If the composition of the bacteria changes, these signals inevitably change as well.

This explains why sweeteners can lead to altered glucose tolerance or a different regulation of energy metabolism in some people – while others hardly react.

Metabolic effects of isolated additives

In addition to the effects on the intestinal flora, other isolated molecules in diet drinks also act somewhat differently than their bound counterparts in food:

• Phosphoric acid can affect the calcium/phosphate balance if consumed regularly and without a mineral-rich diet.
• Caffeine has a more immediate effect because there are no accompanying substances that modulate its absorption.
• Sweeteners provide sweetness without calories – this can influence the perception of sweetness and the insulin response.

Matrix vs. direct effect

The difference lies not primarily in the molecules themselves, but in their biochemical environment :

• In natural foods, the matrix ensures regulation, dampening and interaction with many accompanying substances.
• In diet drinks, isolated molecules have a more direct effect – with direct contact with the intestinal flora and metabolism.

Conclusion

Beverages with sweeteners are low in calories and therefore an alternative to sugary soft drinks. But they are not "empty water": their isolated molecules interact directly with our biochemistry.

Takeaway: Every change in the intestinal flora also means a change in metabolism. Diet drinks save calories – but they are by no means ineffective. What matters is not only which substances they contain, but also how they interact with the body: as part of a complex matrix or isolated in the drink.