The effect of removing or reducing lactose from milk in young children with acute diarrhoea

Acute diarrhoea, typically due to bacterial or viral infection, is a common childhood illness and, in low-income countries, remains an important cause of death. Over two million children under five years of age die each year in poorer countries because of acute diarrhoea. In richer countries, it does not usually cause death but it is a common reason for young children needing medical advice or hospital admission.

Young children with acute diarrhoea may temporarily be unable to digest lactose, the most common type of sugar in milk. Inability to digest and absorb lactose can make the diarrhoea worse and last longer. We looked for evidence that reducing children's lactose intake, either by feeding lactose-free milk or by diluting lactose-containing milk, shortens the duration of diarrhoea and prevents complications such as dehydration.

We looked for research up to 13 May 2013 and included 33 trials in our analyses. Twenty-two trials compared outcomes for children given a lactose-free feed with those for children given a lactose-containing feed and 11 trials compared outcomes for children fed a diluted milk feed with those for children given an undiluted milk feed.

We found evidence that feeds that do not contain lactose may reduce the duration of diarrhoea by an average of about 18 hours (low quality evidence). Lactose-free feeds probably lower the risk of children having prolonged or worsening diarrhoea (moderate quality evidence).

We did not find any evidence that diluted milk feeds reduce the duration of diarrhoea (low quality evidence) but these feeds may lower the risk of children having prolonged or worsening diarrhoea (low quality evidence).

The majority of trials excluded breast fed infants, and none were conducted in low-income countries where diarrhoea can cause death, so the review is relevant to infants and young children who are receiving formula or are weaned in high- and middle-income countries.

Authors' conclusions: 

In young children with acute diarrhoea who are not predominantly breast-fed, change to a lactose-free diet may result in earlier resolution of acute diarrhoea and reduce treatment failure. Diluting lactose-containing formulas may also have some benefits but further trials are required to have confidence in this finding. There are no trials from low-income countries, where mortality for diarrhoea is high, and malnutrition is more common.

Read the full abstract...

Young children with acute diarrhoea, typically due to infectious gastroenteritis, may temporarily stop producing lactase, the intestinal enzyme that digests lactose. This means they may not digest lactose, the main sugar in milk, and this may worsen or prolong the diarrhoeal illness. However, there is uncertainty whether avoiding lactose-containing milk or milk products helps young children recover from acute diarrhoea more quickly.


To assess if avoiding or reducing intake of lactose-containing milk or milk products shortens the duration and severity of illness in young children with acute diarrhoea. We also sought other indicators of morbidity and overall mortality.

Search strategy: 

We searched the Cochrane Infectious Diseases Group Specialized Register (14 May 2013), Cochrane Central Register of Controlled Trials (CENTRAL) published in The Cochrane Library (Issue 4, 2013), MEDLINE (1996 to 14 May 2013), EMBASE (1974 to 14 May 2013), and LILACS (1982 to 14 May 2013), and the reference lists of potentially relevant trials, key conference proceedings, and wrote to individuals and organizations in the field.

Selection criteria: 

Randomized or quasi-randomized controlled trials that assessed the effects of avoiding or reducing exposure to lactose in young children under five years with acute diarrhoea.

Data collection and analysis: 

We extracted data using the standard methods of the Cochrane Infectious Diseases Group, and two review authors independently evaluated trial quality and data extraction. Continuous outcomes were compared using mean difference (MD), and dichotomous outcomes using the risk ratio (RR). We presented all results with 95% confidence intervals (CI) and assessed the quality of evidence using the GRADE approach.

Main results: 

We included 33 trials enrolling 2973 children with acute diarrhoea. Twenty-nine trials were exclusively conducted on inpatients, all from high- or middle-income countries. Fifteen trials included children aged below 12 months, and 22 excluded children who were being breast-fed.

Compared to lactose-containing milk, milk products, or foodstuffs, lactose-free products may reduce the duration of diarrhoea by an average of about 18 hours (MD -17.77, 95% CI -25.32 to -10.21, 16 trials, 1467 participants, low quality evidence). Lactose-free products probably also reduce treatment failure (defined variously as continued or worsening diarrhoea or vomiting, the need for additional rehydration therapy, or continuing weight loss) by around a half (RR 0.52, 95% CI 0.39 to 0.68, 18 trials, 1470 participants, moderate quality evidence).

Diluted lactose-containing milk has not been shown to reduce the duration of diarrhoea compared to undiluted milk or milk products (five trials, 417 participants, low quality evidence), but may reduce the risk of treatment failure (RR 0.65, 95% CI 0.45 to 0.94, nine trials, 687 participants, low quality evidence).