Lactose drives Enterococcus growth and worsens graft-versus-host disease
What it found
In patients and mice, lactose feeds Enterococcus bacteria, which can worsen graft-versus-host disease after stem cell transplant.
A lactose-free diet reduced this in mice.
What they found
Studies in people
Enterococcus domination in patients
Up to 65% of transplant patients had Enterococcus bacteria dominate their gut. This was linked to more graft-versus-host disease and lower survival.
Lactose malabsorption in patients
Patients with a genetic trait for lactose malabsorption had longer-lasting Enterococcus domination after antibiotics. This suggests lactose in the gut helps the bacteria persist.
Animal and lab studies
Lactose feeds Enterococcus
In lab tests, Enterococcus bacteria did not grow without lactose. In mice, a lactose-free diet reduced Enterococcus growth and eased graft-versus-host disease.
Mouse models of GVHD
In mice with graft-versus-host disease, Enterococcus expanded and worsened disease severity. This happened even without antibiotics.
Studies in people and animals
Loss of protective bacteria
Enterococcus domination was accompanied by a loss of Clostridia bacteria and a drop in butyrate, a substance that helps protect the gut.
What the authors conclude
“We report lactose as a common nutrient that drives expansion of a commensal bacterium that exacerbates an intestinal and systemic inflammatory disease.”
Also in their conclusions
- They conclude that Enterococcus domination is a significant risk factor for acute graft-versus-host disease and mortality after transplant.
- They suggest that a lactose-free diet could be a non-antibiotic strategy to reduce Enterococcus growth and improve outcomes.
How it was done
The authors wanted to understand how gut bacteria imbalances lead to disease, especially after stem cell transplants where Enterococcus bacteria often take over and are linked to worse outcomes.
They studied 1,325 adult stem cell transplant patients across four centers, tracking their gut bacteria and health outcomes. They also used mice with similar transplants to test how lactose affects Enterococcus growth and graft-versus-host disease.
What it can’t tell you
- This study shows links between lactose, Enterococcus, and graft-versus-host disease, but it cannot prove that cutting lactose will prevent or treat the disease in people.
- The mouse experiments may not reflect exactly what happens in humans.
- The genetic association in patients does not prove cause and effect.
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 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error