Sweeteners can touch gut bacteria
Scientists at the University of Cambridge tested 39 sweeteners in the lab. They wanted to see if these sugar substitutes affect the tiny microbes that live in our intestines.
What the researchers did
They grew 25 different kinds of gut bacteria, some helpful and some neutral. Each bacterium was given one of the sweeteners. The team measured how fast the bacteria grew.
About three‑quarters of the sweeteners changed the growth of at least one type of bacteria. Some stopped growth completely.
Mixing sweeteners with other foods and drugs
People rarely eat a sweetener alone. It can appear with caffeine, vanilla, or medicines. The scientists mixed sweeteners with eight common drugs and with caffeine and vanilla.
They found more than 100 situations where the effect of a sweetener got bigger or smaller when another substance was present. In 34 cases the effect got stronger; in 68 cases it got weaker.
Biggest surprise: a drug combo
The strongest impact happened when the sweetener isosteviol was paired with duloxetine, a common antidepressant. Together they sharply cut down two important bacteria: Roseburia intestinalis and Parabacteroides merdae. These bugs help with digestion, blood‑sugar control, and the immune system.
What this could mean for health
When the two compounds were added to a simple community of 25 bacteria, the overall variety of microbes fell. Less diversity usually means a weaker, less‑resilient gut.
In lab tests the combo also made some human cells more toxic and disturbed cells that control inflammation.
Are sweeteners dangerous?
The scientists say their work does not prove that sweeteners hurt people. The experiments were done in test tubes, not in real bodies.
In a living gut, sweeteners might be broken down, diluted, or absorbed before they reach the microbes. A person’s diet, genetics, medicines, and existing gut bacteria could all change the outcome.
What comes next?
More studies with real volunteers are needed. Researchers will have to find out:
- If the same bacterial changes happen in humans.
- What doses of sweeteners cause an effect.
- Whether the changes affect weight, blood sugar, or immune health.
The research was funded by the EU Horizon 2020 program and the UK Medical Research Council.