Lactose digestion, intolerance symptoms and gut bacteria in people
What it found
Lactose helps the body take in minerals and feeds helpful gut bacteria in people.
When the gut lacks the enzyme to break it down, undigested lactose can cause gas, pain and loose stools.
What they found
Studies in people
Feeding helpful gut bacteria
Lactose acts as food for helpful gut bacteria like bifidobacteria and lactobacilli in people. Taking in lactose by mouth can raise the numbers of these bacteria in the gut.
Symptoms of intolerance
When people lack the enzyme to break down lactose, it reaches the large intestine and draws in water. Bacteria there ferment it and make gases, leading to loose stools, belly pain, bloating and cramps within 30 minutes to 2 hours after eating it.
Yogurt is easier to digest
People who cannot digest lactose often handle yogurt better. The live bacteria in yogurt carry their own enzyme to break down lactose, and its thicker texture slows digestion so the gut has more time to process it.
Animal and lab studies
Mineral absorption in animals
Animal studies showed that formulas with lactose helped the body take in more calcium, zinc and magnesium than formulas without it. Studies in people have not confirmed these results yet.
Gut defence in lab cells
In lab tests using human colon cells, lactose turned on a gene that makes a germ-fighting protein. This happened no matter how much lactose was used or for how long, suggesting it may help protect a baby's gut from harmful germs.
Other findings
Lactose amounts in milks
Human milk holds about 7 g per 100 mL of lactose, while cow's milk has 4.6 g per 100 mL. First infant formulas contain between 5.4 and 8.2 g per 100 mL.
What the authors conclude
- They advise that any cut in lactose intake should only be temporary and that breastfeeding should always continue even during bouts of diarrhea.
- They warn against swapping milk for plant-based drinks in children and teens because those drinks lack the right mix of nutrients for growth.
- They suggest that slowly adding lactose back into meals can help the gut adjust and ease stomach symptoms over time.
How it was done
The authors wanted to clear up confusion because many people wrongly blame lactose for stomach problems. This fear leads families to cut out dairy or stop breastfeeding without good reason, which can harm a child's growth.
A team of doctors and nutrition experts gathered to read and discuss published research on lactose. They looked at how the body digests it, what happens when people cannot break it down, and how gut bacteria handle it. They then wrote this summary to guide how to manage lactose intolerance in children and adults.
What it can’t tell you
- This work gathers past research rather than running new trials, so it cannot prove that lactose causes specific health changes on its own.
- Animal findings about better mineral absorption have not yet been shown to happen the same way in people.
Who paid
- Funding
- Funded by Nutricia Bagó (from the PubMed record).
- Conflicts
- Nutricia Bagó provided the place to carry out meetings and helped to develop the charts. Nutricia Bagó did not have any participation in the writing of this article and did not interfere with the editorial management. None of the authors has a business relationship with Nutricia Bagó, except for their participation in conferences organized by the company and other events organized by other companies.
- Authors work at
- Hospital de Niños Sor María Ludovica, Argentina; Hospital Italiano de Buenos Aires, Argentina; Instituto de Lactología Industrial (CONICET-UNL), Argentina
The paper
- Title
- Lactose intolerance: myths and facts. An update
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Toca MDC, Fernández A, Orsi M, Tabacco O, Vinderola G (2022). Lactose intolerance: myths and facts. An update. Archivos argentinos de pediatria. doi:10.5546/aap.2022.eng.59Free full textPubMed 35068123DOI
Summary written 1 Oct 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error