By Samantha Chivers, RESULTS Global Health Campaign Manager

Today, on World Toilet Day, it is worth noting that a shocking 2.5 billion people still do not have access to a safe, private toilet. That’s more than one in three people in the world who live every day without basic plumbing to flush, to wash their hands, to bathe their kids in clean water. If the current trend continues it is estimated that by 2015, 2.4 billion people will lack access to improved sanitation facilities.

Over one billion of these people currently have no choice but to actually defecate outside, often in the open with no privacy.

RESULTS does a lot of work on nutrition and child health. But perhaps what’s not so obvious is why we’re talking about water, sanitation and hygiene, or even about World Toilet Day.

Like nutrition, sanitation is not a sexy issue. No-one talks about their toilet over dinner, or about children squatting in fields around a UN conference table.

The thing is, if you use open defecation, or don’t have access to clean water to do away with your… goods, or even to wash your hands, you’re much more likely to get sick. Lack of sanitation and hygiene means you’re likely to get all sorts of diseases, including cholera, typhoid, polio, diarrhoea and worm infestation. If your body is always fighting infections like that, how does it have the energy or resources to grow and develop?

RESULTS Australia and WaterAid Australia have recently published a paper, A comprehensive approach to addressing under-nutrition, looking at the links between water, sanitation and hygiene (known as WASH), and undernutrition.

What we found is that infections literally drain health from your body: bacterial infections and parasites damage the small intestine and reduce its capacity to absorb nutrients; diarrhoeas dehydrate and evacuate nutrients unabsorbed; and worms and other intestinal parasites steal nutrients.

We also found that children in India, a country where more than half of the population defecates in the open, children are much shorter than they should be.

Every day children are drinking water that has been mixed with their neighbour’s faeces. Turns out that these infections permanently reduce your physical growth, impair cognitive development, and lead to long-term undernutrition.

WTD6.3 million children under the age of five died in 2013. Diarrhoea, a disease caused by ingested contaminated water, is the second biggest single killer of children under the age of 5, accounting for 693,000 deaths each year.

However, the elephant in the room, the thing that kills the majority of children, often goes unacknowledged. Undernutrition is the ultimate cause of 45% of these 6.3 million deaths.

Undernutrition, diarrhoea and sanitation are intimately linked. Diarrhoea is caused by drinking water with bacteria or viruses. Each bout of disease drains your energy and nutrient stores, and if you’re constantly exposed to dirty water, you’re going to have a constant bouts of diarrhoea. At the same time, if you haven’t been eating good food you’re probably already deficient in some vitamins or minerals, which increases your susceptibility to diseases like diarrhoea and measles. It’s a vicious, vicious cycle.

A great deal of the staggering burden of undernutrition can be easily dealt with more sanitation, more clean water, and improving hygiene practices.

RESULTS wants to see the Australian government being a leader in saving children’s lives. This would mean having a strong strategy for child health, based on the evidence that a lack of clean water, sanitation and hygiene causes undernutrition.

The government has stated its commitment to focus on nutrition. If we want our aid to be most effective, we need to invest in things that work, and toilets work.

Check out our paper here: A comprehensive approach to addressing under-nutrition in Development Futures Bulletin

And for a sense of where other people’s toilets are, check out the BBC’s photo guide

Photo Credit: WaterAid/Tom Greenwood