How the small intestine handles fructose before it reaches the liver in mice
What it found
In mice, the small intestine breaks down fructose before it reaches the liver, and taking in fructose slowly rather than all at once reduced fat buildup in the liver.
The same amount of fructose caused more liver fat when drunk as a liquid than when eaten as a solid gel.
What they found
Animal and lab studies
Gut shields the liver
When mice lacked the main fructose-processing enzyme in their gut, more than twice as much fructose passed straight to the liver. This led to higher levels of newly made fats in the blood and more fat stored in the liver after 8 weeks on sweetened water.
Boosting gut breakdown helped
Mice engineered to have extra copies of this gut enzyme cleared fructose faster. After 5 days of high-dose fructose by feeding tube, these mice made far less new fat in the liver than normal mice.
Speed of intake matters
Giving mice one large dose of fructose triggered fat production in the liver. Splitting the exact same total amount into four smaller doses every 15 minutes prevented this response.
Drinking versus eating
Over 7 days, mice given sweetened water produced more newly made fat than mice eating the same amount of sugar in a solid gel. The slower intake from the gel kept fat production lower without changing how much sugar was taken in overall.
What the authors conclude
- They conclude that the gut acts as a shield, breaking down fructose so the liver is not overwhelmed.
- They suggest that taking in fructose slowly, matched to what the gut can handle, may reduce fat buildup in the liver.
- The authors advise that people with gut problems might need to be especially careful with sweets, and call for longer studies in humans.
How it was done
Fructose intake has risen 100-fold over the last century, and population studies link high intake to fatty liver disease, obesity and diabetes. Scientists wanted to know whether the gut breaking down fructose protects the liver or makes things worse.
Researchers studied mice with genetic changes that either removed or boosted a key fructose-processing enzyme in the gut lining. They gave the mice sweetened water containing 10% sucrose for up to 5 months, or gave them set doses of fructose by feeding tube. They also compared giving fructose all at once versus spreading the same total amount over 45 minutes.
What it can’t tell you
- All of these experiments were done in mice, so they cannot show exactly what happens in people who eat or drink fructose.
- The study measured short-term fat production and liver fat buildup, but it cannot show whether these changes lead to long-term disease in humans.
Who paid
- Funding
- Funded by NIDDK NIH HHS (from the PubMed record).
- Authors work at
- Princeton University, USA; University of California, USA; University of Pennsylvania, USA
The paper
- Title
- The small intestine shields the liver from fructose-induced steatosis
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Jang C, Wada S, Yang S, et al (2020). The small intestine shields the liver from fructose-induced steatosis. Nature metabolism. doi:10.1038/s42255-020-0222-9Free full textPubMed 32694791DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error