On World Toilet Day, we’d like to take a moment to celebrate the toilet for not only saving lives – by reducing the risk of deadly diarrhea – but also for helping people to grow taller, a key measure of childhood malnutrition. Indicators of overall childhood well-being, height and weight tell us about the critical period of life when bodies and brains are developing. New studies emphasize the relationship between toilets and height, suggesting that a large share of childhood stunting in India can be attributed to the high rates of open defecation. Worse, the effects are likely larger if you live in an area where many others defecate in the open.

“Stuff from your body I'll happily take,

Liquid or solid, whatever you make.

When you think of all the things that I do,

It's time to say thanks to your loo.” Related Experts Victoria Fan Non-Resident Fellow

In developing countries, one in five people defecate in the open for lack of access to a functioning toilet. Sixty per cent of the world’s population that openly defecates lives in India, with economic costs on the order of US$50 billion each year.

These levels of open defecation (and low levels of toilet use) persist in India, even as different ventures of varying scale and impact to improve sanitation have been pursued – latrines have been built for free or provided subsidies, the country introduced open defecation patrols and even tried to scare bachelor men through the “No Toilet No Bride” campaign. Worse, the problem persists even though hygiene and sanitation promotion are ranked as two highly cost-effective public health interventions by the World Bank – $3 per averted Disability-Adjusted Life Year (DALY) for improved hygiene and $11 per DALY averted for improved sanitation. These figures demonstrate that toilets are incredibly affordable and life-saving.

New research shows that toilets reduce malnutrition and help children grow taller. This paper by Dean Spears attempts to unpack the paradox of why children in India are shorter on average than children in Africa, who are poorer on average. Spears found that much of the cross-country variation in height can be explained by the differing levels of open defecation. After controlling for GDP, the paper suggests that the difference in Nigeria and India’s open defecation rate is associated with an increase in child height that is equivalent to the effect of quadrupling GDP per capita. Crucially, the paper suggests that there are large negative externalities associated with open defecation: an increase in the number of people engaging in open defecation per square kilometer is associated with a decrease in child height. So your neighbor’s behavior matters greatly for your own child.

While such cross-country analyses are not causal, other research by Dean Spears and Jeff Hammer try to estimate the causal effect of sanitation on height by evaluating the implementation of a Total Sanitation Campaign in one district of a large state in India (Ahmednagar, Maharashtra). They estimate that the campaign was associated with an increase of 1.3 cm in the height of a four-year-old (specifically, a 0.3 to 0.4 standard deviation increase in children’s height-for-age z-scores). Granted, this estimate should not be taken as the last word, given a number of the study’s methodological qualifications and challenges.

Nevertheless these studies on sanitation’s role in malnutrition, as measured by height, helps to quell a mischievous notion that Indians are somehow genetically predisposed to being shorter. Indeed, in a recent series in the Economic & Political Weekly, a number of outstanding researchers, including Angus Deaton, Jean Drèze, Seema Jayachandran and Rohini Pande show that the broader determinants of malnutrition in India (such as sanitation) continue to win over the (fairly 19th century) genetic arguments.

There are still few research studies testing whether toilets help one and others grow taller, as shown in a recent Cochrane systematic review. The review also found that, among studies on the effects of interventions that improve access to water, sanitation and hygiene on nutritional status, the study period was very short (9-12 months), suggesting that there is still room for better evidence and the usual research caution.

The relationship between malnutrition and diarrheal disease (as distinct from the interventions of sanitation and hygiene) has arguably stronger evidence. One study on 2-year-olds found that five or more episodes of diarrhea is associated with a 25% probability of stunting. Additionally, poor sanitation and water access may lead to environmental enteropathy, an inflammatory response in the gut that makes one’s gut less able to absorb nutrients from an early period.

New longitudinal studies on this relationship continue to be published, including the GEMS study which found that children with diarrhea who were shorter than average were also more likely to die within the study period and that child height is a serious risk factor for death from diarrheal disease. And the MAL-ED study found that intestinal inflammation due to diarrhea was associated with stunting among infants.

Bottom line: Toilets, diarrhea, height and weight, and mortality are interrelated, though scientific evidence of the precise direction and mechanism of these causal pathways will not be easy to disentangle. So on World Toilet Day, like Matt Damon, let’s give a sh*t about toilets. They not only save millions of children, but they make them healthier and taller too.

Victoria Fan is a research fellow and health economist and Rifaiyat Mahbub is a research assistant at the Center for Global Development. The authors thank Dean Spears, Claire Chase, Stephanie Psaki, and Jenny Ottenhoff for helpful comments. You can follow Victoria Fan at @FanVictoria and Rifaiyat Mahbub at @rifaiyat_mahbub on Twitter.