Image caption Poor growth is linked to dirty water

Access to clean water and soap not only improves hygiene but may boost growth in young children, research suggests.

A review of global data found evidence of a small increase in height - about 0.5cm - in under-fives living in households with good sanitation.

The studies took place in Bangladesh, Ethiopia, Nigeria, Chile, Guatemala, Pakistan, Nepal, South Africa, Kenya and Cambodia.

Poor growth affects 265m children globally with long-term health impacts.

The evidence from 14 studies involving nearly 10,000 children comes from a review of evidence known as the Cochrane review, led by the London School of Hygiene & Tropical Medicine (LSHTM) and the international charity WaterAid.

Repeated illnesses

Dr Alan Dangour, a public health nutritionist at the LSHTM who led the report, said providing clean water, sanitation and hygiene is an effective way to reduce deaths from symptoms such as diarrhoea.

It makes absolute sense that there should be a link between dirty water, diarrhoea and growth outcomes but it's interesting that it's never been shown before Dr Alan Dangour, Report author

The analysis suggested, for the first time, that better access to these services may also have a small but important impact on the growth of young children, he said.

"What we've found by bringing together all of the evidence for the first time is that there is a suggestion that these interventions improve the growth of children and that's very important," he told BBC News.

"This is the first time really that evidence has been provided to support the provision of water sanitation and hygiene interventions to improve growth."

He said there is a clear link between a child drinking dirty water, getting diarrhoea and having poor growth, because repeated illnesses in early childhood can impair growth.

'Scourge of malnutrition'

"It makes absolute sense that there should be a link between dirty water, diarrhoea and growth outcomes but it's interesting that it's never been shown before," said Dr Dangour.

"Half a centimetre doesn't sound a lot but in our estimates that increase in growth equates to a reduction in stunting of about 15%, which is quite important."

Commenting on the research, Dr Francesco Branca, director of nutrition for health and development at the World Health Organization (WHO), said: "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."

Poor height growth, or stunting, affects 165m children worldwide, increasing the risk of death and reducing productivity in adulthood, according to the WHO.

Undernutrition is a cause of 3.1m deaths annually - nearly half of all deaths in children under five.