The Study
Added sugars, gut microbiota, and host health
This study didn't test if sugar directly causes changes in gut bacteria—it just looked at lots of other studies that watched people and animals eat sugar and saw what happened. It says sugar might be linked to changes in gut bugs, but it can't prove sugar is the cause.
Analysis score
Maximum 5 for a narrative review.
Where the score came from
When you eat a lot of added sugar, especially in drinks, it changes the good bacteria in your gut, making some bad ones grow and others disappear.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 51 / 100
Quality score
Systematic reviews and meta-analyses of cohort studies. They sit above a single cohort study but below a single randomized trial, because the underlying evidence is still observational.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This change may leak toxins into your blood, causing inflammation linked to obesity, diabetes, and liver disease.
- 2Sugar-rich diets increase bacteria like Enterobacteriaceae and reduce bacteria like Ruminococcus that make protective gut fats.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Gut Microbes
Year
2025
Authors
Yanbo Zhang, Ryan W Walker, Robert C. Kaplan, Qibin Qi
Related Content
Claims (7)
If you cut out starchy foods and sugary snacks for a long time, the good bacteria in your gut have less to feed on, which may lead to less harmful toxins and less body-wide inflammation that's linked to autoimmune problems.
Eating a lot of added sugar, especially in sodas and sweet drinks, might change the good bacteria in your gut, letting some bacteria that love sugar grow too much while reducing others that help keep your gut healthy—this could lead to leaks in your gut lining and inflammation that’s tied to diseases like diabetes.
Drinking sugary sodas might change your gut bacteria more than eating the same amount of sugar in candy or cookies, because the liquid sugar goes through your stomach faster and reaches your intestines in bigger amounts.
Eating too much added sugar might kill off the good bacteria in your gut that make helpful chemicals, which could weaken your gut lining and cause body-wide inflammation.
Whether sugar makes certain good gut bacteria grow or shrink depends on your genes—specifically, a gene called Fut2 that affects the mucus in your gut. So, sugar might help bacteria in some people but hurt them in others.
Eating too much added sugar can irritate your gut, making it more oxygen-rich, which helps bad bacteria thrive and hurts the good ones—this imbalance might contribute to metabolic problems like obesity or diabetes.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.