Randomised controlled trialindependent cross-checkabstract checked★ key study I-SOD-121 in-depth review
Fructose and table sugar drinks boost fat production in the liver
Fructose- and sucrose- but not glucose-sweetened beverages promote hepatic de novo lipogenesis: A randomized controlled trial.
Overview
Geidl-Flueck B et al.. J Hepatol 2021 · PMID 33684506 · DOI 10.1016/j.jhep.2021.02.027
In a 7-week trial, men drinking 80 g/day of fructose or table sugar in drinks doubled their liver's fat production; glucose did not.
Does the study support the specific claim? Partly · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test whether fructose drives liver fat production regardless of calories.
- How was the study done?
Randomised blinded trial of sugar-sweetened drinks.
- How many people, animals or samples were studied?
94 healthy men.
- What was actually found?
Fructose and sucrose doubled liver fat synthesis; glucose did not.
- How large was the observed effect?
FSR 20.8 and 19.7 vs 9.1 %/day.
- What do the results mean in everyday life?
Fructose-containing sugars in drinks push the liver to make fat.
- What are the study's limitations?
Healthy men; surrogate outcome.
- What does it say about Elawady's specific claim?
Supports the fructose part; shows table sugar acts the same way.
- Do the results apply to Germany and Europe?
European.
- What can explicitly not be concluded from this study?
Cannot show that this causes fatty liver disease.
Scientific in-depth review
1. Full reference
- Authors
- Geidl-Flueck B et al.
- Journal
- J Hepatol
- Year
- 2021
- Identifier
- PMID 33684506 DOI 10.1016/j.jhep.2021.02.027
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
Authors declare no conflicts of interest (PubMed record); Swiss non-governmental funding listed
2. Research question
Does fructose affect hepatic lipid metabolism independently of excess energy intake?
3. Study design and population
- Study design
- Randomised controlled trial – Double-blind randomised controlled trial, 7 weeks (NCT01733563)
- Population
Healthy lean men
- Country
Switzerland
- Period
7 weeks
- Sample size
94
- Inclusion and exclusion criteria
Healthy men
4. Methods and endpoints
- Exposure / intervention
80 g/day of fructose, sucrose or glucose in SSB added to usual diet
- Comparator
SSB abstinence (control)
- Endpoints
Hepatic fractional secretion rate of newly synthesised fatty acids (tracer); lipolysis; FFA oxidation
- Statistical methods
Group comparisons of medians
5. Actual results
- Results
Median basal hepatic FSR (%/day): sucrose 20.8 (p=0.0015 vs control), fructose 19.7 (p=0.013), glucose 11.0 (n.s.), control 9.1. Fructose did not change basal secretion of newly synthesised VLDL-triglyceride, peripheral lipolysis or FA oxidation. Total energy intake similar across groups.
- Absolute risks
not applicable
- Authors' conclusion
Regular consumption of fructose- and sucrose-sweetened beverages in moderate doses increases hepatic fatty acid synthesis even in a basal state; not observed after glucose.
6. Strengths
- Double-blind RCT
- Tracer methodology
- Moderate, realistic dose
7. Weaknesses
- Healthy young men only
- Surrogate outcome (lipogenesis), not liver disease
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Abstract-level judgement.
9. Assessment of the statistical interpretation
About two-fold increase in lipogenesis with sucrose and fructose versus control; glucose no effect.
10. Relevance to the specific claim
Supports the fructose-versus-glucose contrast in C-SOD-04 at moderate doses; but sucrose (table sugar, 50% fructose, also present in honey and juices) acted like fructose, so the effect is not specific to soft drinks.
11. Independent contrary findings
Chiu 2014 (I-SOD-04) and Lee 2022 (I-SOD-122): no effect on liver fat in isocaloric substitution.
12. Transferability to Germany and Europe
European trial.
13. Overall methodological judgement
High-quality mechanistic RCT supporting a fructose-specific effect on liver fat synthesis.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Clinical relevance for fatty liver disease.