Lactose, gut bacteria and graft-versus-host disease in transplant patients and mice
What it found
In people receiving bone marrow transplants, the sugar lactose fed a gut bacterium called Enterococcus, which was linked to worse outcomes.
Removing lactose from the diet reduced this bacterial growth and lessened disease severity in mice.
What they found
Studies in people
Enterococcus linked to worse outcomes
In transplant patients, when Enterococcus made up 30% or more of gut bacteria, survival was lower. These patients also had more severe graft-versus-host disease. Up to 65% of patients showed this bacterial overgrowth after their transplant.
Lactose intolerance prolonged bacterial dominance
The researchers genotyped 602 patients for a gene variant that affects lactose digestion. Patients who could not absorb lactose well kept high levels of Enterococcus for longer after finishing antibiotics.
Animal and lab studies
Lactose feeds Enterococcus bacteria
In lab tests, both E. faecalis and E. faecium stopped growing when lactose was removed from their food source. Genes for breaking down lactose made up about 3% of the bacterial genomes tested.
Lactose-free diet helped mice
Mice fed a lactose-free diet after transplantation had much less Enterococcus growth. Their graft-versus-host disease was also less severe compared to mice eating regular food.
Studies in people and animals
Butyrate dropped during bacterial overgrowth
When Enterococcus took over, beneficial clostridia bacteria decreased in both patients and mice. This was accompanied by a significant drop in butyrate, a substance that helps protect the gut lining.
What the authors conclude
- They suggest that a lactose-free diet could be a new way to limit harmful bacterial growth after bone marrow transplants.
- Their results show that lactose availability drives Enterococcus expansion and worsens graft-versus-host disease in both mice and people.
- The authors propose that removing dietary lactose might improve patient outcomes by starving these bacteria.
How it was done
After bone marrow transplants, patients often develop a serious condition where donor cells attack their body. The authors wanted to understand why certain gut bacteria multiply after these transplants and worsen this condition.
They studied stool samples from 1,325 adult transplant patients across four centers in the USA, Japan and Germany. They also ran experiments in several mouse models of bone marrow transplantation. In lab tests, they grew bacteria with and without lactose to see how it affected their growth.
What it can’t tell you
- These findings come from transplant patients and mouse models of transplantation.
- They cannot show what happens in healthy people eating normal amounts of lactose.
- The mouse diet experiments cannot prove that cutting lactose would have the same effect in human patients outside a transplant setting.
Who paid
- Funding
- Funded by NCI NIH HHS; NHLBI NIH HHS; NIA NIH HHS; NCATS NIH HHS; NIAID NIH HHS (from the PubMed record).
- Conflicts
- Competing interests : M.V.D.B. is on the advisory board of and has financial holdings in Seres Therapeutics Inc., serves as DKMS chairman, has received speaker honoraria from Merck and Acute Leukemia Forum, holds patents that receive royalties from Seres Therapeutics Inc., has received honorarium and research support (1 January 2017 to present) from Seres Therapeutic Inc., and IP licensing with Seres Therapeutics Inc. and Juno. J.U.P. reports research funding, intellectual property fees, and travel reimbursement from Seres Therapeutics and consulting fees from Davolterra. E.G.P. has received speaker honoraria from Bristol-Myer Squibb, Celgene, Seres Therapeutics, MedImmune, Novartis, and Ferring Pharmaceuticals; is an inventor on patent application no. WPO2015179437A1, entitled ‘Methods and compositions for reducing Clostridium difficile infection’ and no. WPO2017091753A1, entitled ‘Methods and compositions for reducing vancomycin-resistant Enterococci infection or colonization’; and holds patents that receive royalties from Seres Therapeutics Inc.. Other authors have no competing interests.
- Authors work at
- Sloan Kettering Institute, USA; Weill Cornell Medical College, USA; German Cancer Research Center (DKFZ), Germany
The paper
- Title
- Lactose drives Enterococcus expansion to promote graft-versus-host disease
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Stein-Thoeringer CK, Nichols KB, Lazrak A, et al (2019). Lactose drives Enterococcus expansion to promote graft-versus-host disease. Science (New York, N.Y.). doi:10.1126/science.aax3760Free full textPubMed 31780560DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error