Researchers have found that children who have access to clean water and soap have improved height growth.
Researchers from the London School of Hygiene and Tropical Medicine, alongside the charity WaterAid, analyzed 14 studies that had been conducted in low- and middle-income countries. Their results have been published in The Cochrane Library.
The studies provided data on 9,469 children under 18 years of age and analyzed the effect of water, sanitation and hygiene programs on their physical growth.
When water quality and access were improved in the household alongside access to soap, the analysis found a 0.5cm increased height growth in children under the age of five.
According to Unicef child nutrition statistics, poor height growth - stunted growth - affects 25% of children under the age of five worldwide. In sub-Saharan Africa and South Asia, almost 40% of children under five suffer from stunted growth.
The Cochrane reviewers say studies have shown that stunted growth in children, which is caused mainly by malnutrition, can result in long-term impacts on physical and mental health development. It is linked to a higher risk of mortality and reduced productivity in adulthood, they say.
Dr. Alan Dangour, a public health nutritionist from the London School of Hygiene and Tropical Medicine, says: "We typically think that providing clean water, sanitation and hygiene is an effective way to reduce the incidence and associated deaths from diseases such as diarrhea - which remains the third biggest killer of under-fives worldwide.
"For the first time, our analysis suggests that better access to these services may also have a small but important impact on the growth of young children."
The researchers estimate that clean drinking water and effective hand washing may reduce the risk of stunting in children under the age of five by up to 15%. Dr. Alan Dangour says:
"This is potentially an extremely important finding, that identifies that improving access to water, sanitation and hygiene could be a key part of the toolkit to tackle the global burden of undernutrition."
Improving access to clean water and soap was likely to contribute to the children's increase in height through lower exposure to microbiological and parasitic infestations in early childhood, the study authors say, since such infestations can negatively impact growth.
Dr. Francesco Branca, director of nutrition for health and development at the World Health Organization, says of the research:
"Until now, we have not had a demonstration of the direct nutrition impact of water, sanitation and hygiene interventions on nutrition."
He adds: "This review shows that a multi-pronged approach is the way to go - bringing together actions to improve food quality and safety as well as feeding and care of children, with others to prevent and treat infections and improve the home environment - to address the scourge of chronic malnutrition."
The study authors caution that the main findings of their review are based on short-term studies lasting 9-12 months, none of which was of "high methodological quality." They say the evidence base may be improved by several large studies that are ongoing.