01/08/2013 11:25 BST | Updated 01/10/2013 06:12 BST

Why Half a Centimetre Matters

A new study this week shows that better access to clean water and adequate hygiene practices in developing countries can help reduce the effects of poor height growth in children, or stunting, caused by poor nutrition.

The report, written by scientists and researchers at the London School of Hygiene and Tropical Medicine, the SHARE Research Consortium and the international development organisation WaterAid, demonstrates that the basic services of clean water and soap can lead to around an average of half a centimeter in increased height in children under the age of five.

While half a centimetre may not sound like much, the Cochrane Review - the gold standard for reviewing and analysing the available evidence base - has demonstrated for the very first time, high quality evidence that links water and hygiene initiatives to child nutrition.

Interventions to improve water quality and supply, sanitation and hygiene practices, and their effects on the nutritional status of children, collected study data on nearly 10,000 children under age five in ten lower and middle income countries and examined the effect of water, sanitation and hygiene programmes on their physical growth.

We now know that lack of access to clean water and soap may contribute to poor growth, which increases the risk of illness and death in childhood, as well as other adverse impacts in later life. Simply put, a lack of these basic services leads to increased rates of infections, which in turn limit our bodies, and more profoundly the ability of young children, to absorb the nutrients from the food they eat.

It is estimated that stunting affects 165 million children worldwide and has long term effects on physical and mental development, reducing productivity in adulthood and even increasing the risk of mortality. Under nutrition is also a contributing cause of 3.1 million deaths annually - nearly half (45%) of all deaths in children under five.

Understanding all of the causes of under nutrition, and putting in place the programmes required to tackle them, is the important step towards reducing the death rate of children under five.

A further analysis of the data by some of the authors, separately estimated that clean drinking water and effective hand washing could reduce stunting in children by up to 15 per cent.

As Chairs of the All-Party Parliamentary Group on Child Health and the All-Party Parliamentary Group on Water and Sanitation, we know just how significant these findings are.

Globally nearly one in four children are stunted, which can cause illness and death. Stunting can also lead to impaired brain development, and is linked to reduced school attendance and performance. Three quarters of the worlds stunted children live in sub-Saharan Africa and South Asia, where 40% and 39% of children under five are stunted respectively.

These findings reinforce what we have argued before - real progress in child health will only be achieved when we create a clean and safe environment that prevents diseases from happening.

So while a half centimetre of extra growth may not seem like much to us, it could have a significant impact on the lives of millions of children in the poorest countries. When we consider this in combination with the other benefits of water, sanitation and hygiene programs, such as reduced levels of diarrhoea, increased health and school participation we can see just how vital these basic services are.

- Bill Cash MP, Chair of the Water and Sanitation All Party Parliamentary Group and Conservative Member of Parliament for Stone

- Jim Dobbin MP, Co-Chair of the Child Health All Party Parliamentary Group and Labour Member of Parliament for Heywood and Middleton

- Lord Avebury, Co-Chair of the Child Health All Party Parliamentary Group, Liberal Democrat Member of the House of Lords